Simionato v The City of Tea Tree Gully & the State of SA - [2004] SADC 93

DISTRICT COURT OF SOUTH AUSTRALIA
(Civil)
SIMIONATO & ORS v THE CITY OF TEA TREE GULLY & THE STATE OF SA
Judgment of His Honour Judge Herriman
30 June 2004
TORTS - NEGLIGENCE - ESSENTIALS OF ACTION FOR NEGLIGENCE - DUTY OF CARE - REASONABLE FORESEEABILITY OF DAMAGE - PARTICULAR CASES - DUTY OF OCCUPIER
Nuisance and negligence - encroachment of tree roots and structural damage - change in ownership of adjoining land - timing of encroachment - right of support - delegable duty
"The Law of Torts" John G Fleming (7th ed. Law Book Co) , referred to.
Young v Wheeler (1987) Aust Torts Reports 80-126; Xuereb v Viola (1990) Aust Torts Reports 81-012; Acton v Blundell (1843) 12 M & W 324; (1843) 152 ER 1223; Hargrave v Goldman (1963) 110 CLR 40; Burnie Port Authority v General Jones Pty Ltd (1992-94) 179 CLR 520; Kondis v State Transport Authority (1984) 154 CLR at 687; Northern Sandblasting Pty Ltd v Harris (1997) Aust Torts Reports 81-435, applied.

DAMAGES - GENERAL PRINCIPLES
Mitigation - contribution - betterment
Murphy v Brown (1985) 1 NSWLR 131; Harbutt's "Plasticine" Ltd v Wayne Tank and Pump Co. Ltd [1970] 1 QB 447; Hoad v Scone Motors Pty Ltd (1977) 1 NSWLR 88; Bellgrove v Eldridge (1954) 90 CLR 613; Rentokil Pty Ltd v Channon (1990) 19 NSWLR 417; British Westinghouse Electric and Manufacturing Co Ltd v Underground Electric Railways Company of London Ltd [1912] AC 673; Payzu Ltd v Saunders [1919] 2 KB 581; Hoad v Scone Motors Pty Ltd (1977) 1 NSWLR 88; TCN Channel 9 v Hayden Enterprises Pty Ltd (1989) 16 NSWLR 130; Banco de Portugal v Waterlow & Sons Ltd [1932] AC 452; Johnson v Perez (1988) 166 CLR 351, applied.

SIMIONATO & ORS v THE CITY OF TEA TREE GULLY & THE STATE OF SA
[2004] SADC 93

The first and second plaintiffs (respectively “Mario” and “Mila”) are husband and wife and the joint owners of a house property situated at 8 Kevin Road, Modbury (“No. 8”). They were involved in constructing their house and have resided in it since about 1976. It faces west.
The third plaintiff (“Liliana”) is their daughter and she owns the house directly opposite theirs at No. 7 Kevin Road (“No. 7”). She has never resided in it: it was purchased by her as an investment in about 1980 and was then let out, more or less continuously, until November 1995. It has remained unoccupied since then. It is believed to have been constructed in the late 1960s.
Both properties are situated on more or less level ground and are the last houses on either side of a cul-de-sac at the southern end of Kevin Road where it abuts the North‑East Busway Reserve.
That Reserve had at one time been the property of the second defendant (“the State”) and had been undeveloped. In about 1980, the State, through one of its agencies, began work to incorporate it into what was then described as the “North‑East Busway Project” (“the Project”), a plan to create a dedicated bus route to the north‑eastern suburbs of Adelaide. The plan involved the excavation of a substantial east‑west ditch, or valley, to the south of Kevin Road and the construction within it of a permanent way for the bus route. The earthworks were thus substantial and resulted in a land contour that was convex in shape and descended southwards from the southern fences of Nos 7 and 8, gradually, at first, over a lineal distance of about ten or eleven metres, but thereafter quite sharply over a similar distance to the busway platform. The upper level of the slope was separated by a wire fence from the steeper, lower section and was set aside for public use. It was designed and implemented as a meandering, undulating, paved bike and walking track (“the track”) within a planted, park‑like setting, the whole area being described as “the linear park”. It is accessible, inter alia, from a pathway at the cul‑de‑sac end of Kevin Road and, at one point just to the east of that point, the track separates into northern (upper) and southern (lower) arms. The linear park is thus a continuous stretch of public land fringing the bus route (itself now known as “the O’Bahn”).
The linear park was designed, constructed, landscaped and planted by the State, with the assistance of consultants, contractors and through its own agencies, between about 1980 and 1989 (on all the evidence, planting of vegetation occurred in 1988 or 1989). In a completed state it was then transferred to the first defendant (“the Council”) in July 1991. The lower section of the excavation, being the O’Bahn route, remains the property of the State.
For relevant purposes, at the points where it passes to the south of Nos 7 and 8, the track meanders in a roughly east‑west direction and up to about 7.5 metres distant from their southern side fences. The intervening space was landscaped and planted in 1988 or 1989 as part of the plan to develop the linear park concept. Various species of native shrubs and trees were planted there for aesthetic purposes and, as well, to screen the nearby residential areas from the park and bus route and to provide them with some measure of noise protection (“the plantings”). As a result of events leading to this litigation, all of the plantings were first cut back to stumps – in about December 1996 – and later, in February or March 1997, completely removed. The relevant spaces are now barren and mulched.
This case concerns the acknowledged impact, upon the building structures at Nos 7 and 8, of the plantings. It is common ground that they caused desiccation of the subsoil beneath those structures, with resulting footing subsidence and wall cracking, but there are substantial disputes as to the precise cause of that desiccation, its timing, the State’s liability for it and the remedial measures that ought to be adopted to repair the house structures.
Before discussing these matters further, I should note the following:
(1)A pre‑construction (or dilapidation) report on No. 8 was undertaken by or on behalf of the State on 21 January 1982, and it became Exhibit D6. A similar inspection was undertaken with respect to No. 7, but, for reasons which did not emerge at trial, no report was either prepared or preserved. None was produced at trial.
(2)In late 1986 and just prior to the commencement of further construction works, an additional inspection of No. 8 took place by engineers D N Sandery & Associates and the report D7 was prepared on 10 December 1986.
(3)Then, during the course of those works, in 1988, the first and second plaintiffs wrote to the Project Director complaining of cracking to No. 8 which they attributed to the vibrations from nearby rolling operations.
In consequence, D N Sandery & Associates again inspected and reported, on 28 March 1988 (D9), that “Since the original inspection, quite substantial cracking has occurred”. Their report suggested, however, that the cracking was due not to construction works, but to plumbing problems within No. 8.
In response, the first and second plaintiffs obtained a report from B C Tonkin, Engineers (P38) which partly supported their assertions as to the cause of cracking, but which suggested that it was of a minor nature and was “not of an order to cause concern from an engineering point of view”. Further, the author of that report commented upon the high volatility of the soil and concluded:
“In addition, during discussion with Mrs. Simionato, mention was made of the intention of the Authority to plant trees in the vicinity of the southern boundary of their property. It is recommended that the selection of flora to be planted is made judiciously as the effect of trees dewatering soil is a major contributor to cracking in Adelaide houses. It is therefore important that should this course of action be pursued by the Authority responsible, it accounts for this fact in the determination of what is to be planted, and where it will be placed in relation to the Simionato’s residence.”
As a result of solicitors’ correspondence, a settlement was then reached whereby the Project Director paid and the first and second plaintiffs accepted $600 by way of compensation for cosmetic and other repairs. I have not treated the terms of that settlement as implying any concession by either party.
In a letter to solicitors for the first and second plaintiffs (at p.2 of P37), the Project Director took up that issue of tree planting and commented:
“I concur that tree planting needs to be carefully considered. It is our intentions (sic) to plant trees at least 4 m clear of the property boundary. At this distance there should be no risk of damage.
Shrubs will be densely planted adjacent to the fences and I am advised that such planting and the associated mulching is likely to ‘even out’ the water content of the soil.”
That exchange has some resonance in the events which were either then taking place or which followed.
It was not clear from the evidence exactly when the plantings took place, but the exhibit P19 and the evidence of the parties, including that of the landscape architect engaged by the State (Dexter), suggest it must have been in or after early to mid‑1988. It was plainly intended that there would be a relatively thick or screen‑like coverage of vegetation in those sections. On the unchallenged evidence of Mila, there were in fact no less than 90 individual plants propagated in the section immediately to the south of No. 8 and as many as 107 to the south of No. 7. Further, both she and Liliana described the “screen” presented by those plantings, once mature, as thick and, indeed, impenetrable. The first engineer to inspect them, Mr J Woodburn (“Woodburn”), also described the plantings as “thick” and “dense” and spoke of the difficulty he had in accessing the site of borehole 2. The exhibits P19, 20, 32, 42 and, indeed, D4 corroborate these descriptions.
There was some small dispute at trial as to the distance between the southern fence of each property and the nearest plantings, but I am satisfied from the evidence of the plaintiffs, of Dexter and, indeed, the photographs produced, in particular P20, 21, 22, 31, 32 and 42, that that distance was in some cases less than one metre.
The north‑south width of the planting beds contiguous to each house, according to the scaled plan in the report of Woodburn (P5), in the case of No. 8 ranged between 2.5 and five metres and, in the case of No. 7, ranged between five and 7.5 metres. Otherwise, I am satisfied, having regard to the evidence of Liliana, Mila, Woodburn and Dexter, most of which was uncontentious, and to the drawing P19 and the exhibits P8, D16 and D17, that those beds contained mixed varieties of Australian native plants, shrubs and trees. Further, it is clear from that evidence and the document P8, that those plantings did not correspond, in all respects, with the varieties specified by Dexter in the plan P19; in particular, they contained specimens of the genera grevillea and eucalyptus and species of acacia and eremophila, none of which were specified. No detailed plan or catalogue of their actual varieties or plantings was produced, but amongst those identified were specimens capable of growing to heights of five metres (Melaleuca armillaris), three to four metres (Myoporum insulare and Hakea suaveolens) and one to two metres (Eremophila maculata). Further, I note the observations of Mr Whitehill (D16) that the roots of Melaleuca armillaris are capable of spreading as much as 6.5 metres and that the roots of shrubs can be as aggressive as tree roots.
No estimate was placed on the achievable height of the lone eucalypt adjacent No. 8, but on the evidence of the plaintiffs and Woodburn, it appears to have grown to a substantial height (Woodburn estimated six metres) prior to being lopped. Whilst that specimen was not specified in P19, it came to be there in somewhat unusual circumstances. According to the evidence of Mila (which I accept), it was actually a ceremonial tree placed there by the Premier of the day and it was placed 1.5 metres south of the fence of No. 8. By any measure, that was an imprudent planting.
There was otherwise no evidence put before me to the effect that other planting departures from the P19 specification were the subject of any horticultural or engineering advice; indeed, Dexter disowned them.
The actual heights reached by those various plantings before they were cut down was not the subject of precise measurement or evidence, but the exhibits P20, P21 and P32, supported by the evidence of Liliana, Mila and Woodburn, make it plain that, except for the six-metre eucalypt, they reached heights of at least three metres; indeed, in Woodburn’s report P5, he says that was the average height.
There is no question but that foliage from these plantings touched the southern fence of each property and, plainly in the case of No. 7 (see Exhibit P20) and probably in the case of No. 8, extended into each property above the fence line. The driveway to each house is located on its northern side and there is a relatively short space between the southern walls of each and its southern fence. In the case of No. 7, on the scaled plans of Dr Mitchell (“Mitchell”) and Woodburn, that distance is one to 1.5 metres and, in No. 8, that distance (see Woodburn) is about one metre.
I accept the plaintiffs’ evidence that these plantings were, at first, very heavily irrigated by the State until they became relatively self‑sustaining, and that this point was reached prior to transfer of the park to the Council in 1991 – exactly when it was, did not clearly emerge. I am satisfied, however, that irrigation continued for much longer than the three‑month period initially proposed by Dexter and, indeed, to a time close to when the land was transferred to the Council. Dexter thought it had been carried out for possibly six or twelve months. At all events, it seems not to have been disputed that, after July 1991, the Council did not irrigate the plantings and they were left to rely on natural moisture sources.
It was common ground amongst the geotechnical experts called by both parties and, indeed, it was an agreed fact, that over the several years after planting occurred and up to at least 1996, the roots of these shrubs and trees took up substantial moisture from the subsoil in the linear park and, in time, caused desiccation of the subsoil beneath each of Nos 7 and 8, leading to shrinkage in volume of that soil and damage to the structures upon it. This impact was exacerbated by two factors:
(1)the propensity of some native varieties to more aggressively seek out subsoil moisture, and notably among these are species of grevillea and hakea (P4.65) and eucalyptus (D1.228); and
(2)the fact that the properties, the linear park and the busway are all situated in an area where the soil profile is typically described as black earth overlying Hindmarsh clay. Such a soil profile is well known to be variable in depth and content over short distances and highly reactive to changes in moisture content, such that the addition of moisture will cause heaving of the soil mass and desiccation will result in shrinking and subsidence.
The house at No. 7 was of a solid masonry construction with timber floors and, so far as could be ascertained, was founded on deep strip footings – a typical form of footing construction in the late 1960s. The first and second plaintiffs had, however, themselves been involved in the construction of No. 8 (in 1976) and were able to say that the footings they used were of a larger than normal size and constructed with a view to the known soil conditions.
In November 1995, all plaintiffs became concerned at what they regarded as new or aggravated cracking in their respective dwellings. In consequence, on 28 November 1995 they wrote to the State via the Department of Transport, complaining of this. The Department thereupon commissioned a report from Woodburn, which was prepared in February 1996 (P5). He expressed the view that the vegetation to the south of each fence line was responsible for the structural problems and recommended its removal as the most appropriate solution. The Department accordingly referred the matter to the Council for attention. The Council at first took little interest in the matter. The plaintiffs then consulted solicitors and in mid‑1996 commissioned a report from John Goldfinch, consulting engineer (“Goldfinch”) (P9.1). He agreed with Woodburn. As of November 1996, he noted, the trees were still in place and, as summer was approaching, recommended their removal as a matter of urgency.
Ultimately, late in that year, the Council arranged for the trees and shrubs to be cut close to ground level and the area mulched.
On the plaintiffs’ accounts, that intervention did not alleviate their problems and, indeed, by early 1997 the stumps were sprouting new growth, suckers were emerging in other locations, including inside the property at No. 7, and their house cracks were continuing to expand. They complained again to the Council. In consequence, there was a site meeting held on 29 January 1997, attended by engineers Goldfinch and Trevor John (“John”) and representatives of the Council and the State, at which the matters recorded in Goldfinch’s letter of 4 February 1997 (P9) were agreed. The agreement was to the effect that all vegetation and shallow roots be removed in both areas (that is to say, that the stumps and adjacent root material be taken out), that they be mulched and that moisture be reintroduced to the subsoil by irrigation lines, installed 300 millimetres south of each fence with variable flow drippers. A flow rate was agreed and the Council undertook to provide the irrigation materials and contribute to the water.
That agreement was put into effect, the grubbing and mulching were done and the plaintiffs thereafter installed, activated and monitored the irrigation system.
Soon afterwards, say the plaintiffs, the cracks in their respective properties ceased to widen and, indeed, began to close up.
The irrigation recommendations were, I am satisfied, diligently complied with by the plaintiffs, Mila attending to this, adjacent to both properties, three times per day and more frequently in hot weather, over two years. In the event, partial closure of all cracking was achieved.
In about August 1999, Goldfinch advised the plaintiffs that it appeared that the suction capacity of the subsoil had by then reduced to a negligible figure and that the introduction of further water was not likely to be accepted or effective. That assessment was considered by Woodburn, who then conducted moisture suction tests. He agreed with the Goldfinch opinion.
Mitchell had by this time been engaged by the State. He was not at first aware of the irrigation measures then in place and first reported under the misapprehension that natural moisture recharge had been partly effective, albeit, he went on to say, that a specific form of irrigation (involving the introduction of water at points closer to the house footings) would speed up the process of soil rebound and crack closure. Ultimately, when he learned of his misapprehension, he adhered to his original prescription, expressing the view that further moisture could still be added and would achieve further rebound. His specification was not adopted by the plaintiffs, who accepted and acted upon the Goldfinch/Woodburn opinion that furthering artificial watering would not likely achieve additional structural improvement.
In the event, each house remains cracked and the plaintiffs contend that no further irrigation will improve the status of either. The State disputes this, relying upon Mitchell’s opinion.

All engineers agree that removal of the vegetation and rewetting of the subsoil did indeed result in some correction of footing subsidence and crack closure, but it is plain that complete correction and closure has not been achieved. There is a dispute as to whether further irrigation will improve that position and, in any event, as to what should be done to repair the properties, either in their present conditions or if further closure were achieved.
The plaintiffs have sued in nuisance and negligence, contending that the State is liable for the structural and other damage caused to their respective properties by footing settlement and that it should compensate them by indemnifying for the costs of underpinning and repairing them.
By a previous judgment in this action (Judgment No. 156 of 2001), it was held that the Council was not liable for this damage at the suit of the plaintiffs, by virtue of s.315(3) of the Local Government Act 1934. In consequence, this action proceeded against the State, only.
The State has denied responsibility as a matter of law and fact, contending that it owed no duty of care to the plaintiffs (or if it did, it was not breached), that no act of nuisance had been proven as of July 1991, that any damage to either premises was the result of inadequate footing design, reactive soil and the failures of the plaintiffs to properly repair leakages and otherwise maintain their gardens. It says there is no evidence of root encroachment and contends that, in any event, it properly delegated any duties it owed with respect to the plantings to its landscaping consultants and that in July 1991 it transferred ownership of the linear park to the Council, which thereafter assumed responsibility for it and for the actions of the plantings upon it. Finally, it disputes the plaintiffs’ remediation proposals and argues they failed to properly mitigate the asserted damage by following the Mitchell recommendations.
Evidence was given by each of the second and third plaintiffs, reports were tendered and evidence led from consulting engineers Goldfinch and Woodburn, as well as a valuer, Mr Horner, and other documents were tendered by consent. The State called Mitchell and Dexter, and a statement of agreed facts (P1) was tendered.
It is unnecessary to canvass the lay evidence in any detail. In the most part, it was non-contentious and the principal issues fall to be determined upon the expert evidence.
I will come to discuss the factual issues in a moment, but first I should touch upon the legal ones.
LEGAL PRINCIPLES - LIABILITY
It is useful at this stage to discuss those legal issues touching upon the question of liability.
The plaintiffs’ claims in this matter are brought in negligence and nuisance. They warrant discussion of legal principles.
- Nuisance
An appropriate starting point might be “The Law of Torts”, John G Fleming (7^th ed., Law Book Co.) at page 379:
“Few words in the legal vocabulary are bedevilled with so much obscurity and confusion as ‘nuisance’. Once tolerably precise and well understood, the concept has eventually become so amorphous as well nigh to defy rational exposition.”
Nevertheless, the author of that text goes on to proffer a definition which for present purposes is of some assistance. At page 385:
“The gist of private nuisance is interference with an occupier’s interest in the beneficial use of his land ... (p.386) ... The interest in the beneficial use of land protected by the action of nuisance is a broad and comprehensive notion. It includes not only the occupier’s claim to the actual use of the soil for residential, agricultural, commercial or industrial purposes, but equally the pleasure, comfort and enjoyment which a person normally derives from occupancy of land, not excluding recreational amenities like television reception. Accordingly, harmful interference may be manifold: it may consist in physical damage to land, buildings, and chattels thereon, through vibrations, flooding, fire and the like; or in disturbance of the comfort, health, and convenience of the occupant by offensive smell, noise, smoke, dust, by reasonable fear for one’s safety or health, or even by the use of an adjoining residence for prostitution.”
In that same context, it is accepted law that:
“an owner of land on which a tree grows is liable, if its roots encroach on adjoining land and cause damage, to an action of damages for nuisance at the suit of the owner of the adjoining land. That such an encroachment is not regarded as a trespass but as a nuisance is settled law ...” (cf Young v Wheeler (1987) Aust Torts Reports 80-126 at 68,969 per Wood J).
That statement is supported by numerous authorities in the United Kingdom and Australia, and without seeking to traverse them all, I refer to Davey v Harrow Corporation [1958] 1 QB 60; Morgan v Khyatt [1964] 1 WLR 475; Leakey v National Trust [1980] QB 485; Proprietors of Strata Plan No. 14198 v Cowell (1989) 24 NSWLR 478; City of Richmond v Scantelbury [1991] 2 VR 38; Malliate v Sharpe [2001] NSWSC 1057 and Valherie v Strata Corporation No. 841 [2004] SASC 170.
Even so, complications have arisen from time to time in considering the potential liability of a person acquiring land from a vendor who has, himself, initiated the mischief. The ordinary liability of the vendor for any nuisance committed by him has not been doubted, but the purchaser has been held to be liable for the continuance of a nuisance only if he has known or ought to have known of its existence and has failed to take such steps as were reasonable to eliminate the risk of reasonably foreseeable damage (cf City of Richmond, Malliate and Valherie, supra).
That distinction between the liability of an instigator of a nuisance and a party continuing it has potential relevance in this matter, because it is common ground that the plantings upon which these claims focus were made by the State in about 1988 or 1989 and that the land on which they were placed was transferred to the Council on 24 July 1991.
- Rights of support
Whilst the law has traditionally recognised the right of an owner of land, as against his neighbour, to the maintenance or support of the surface of his land in its natural condition, there are important limitations on that principle and one of them falls for consideration in this case.
Its history is usefully discussed in Xuereb v Viola (1990) Aust. Torts Reports 81‑012 per Giles J at 67,680, but the earliest expression of the principle appears to have been in Acton v Blundell (1843) 12 M & W 324 at 353; (1843) 152 ER 1223 (at 1235), where the court described the:
“... principle, which gives to the owner of the soil all that lies beneath his surface; that the land immediately below is his property, whether it is solid rock, or porous ground, or venous earth, or part soil, part water; that the person who owns the surface may dig therein, and apply all that is there found to his own purposes at his free will and pleasure; and that if, in the exercise of such right, he intercepts or drains off the water collected from underground springs in his neighbour’s well, this inconvenience to his neighbour falls within the description damnum absque injuria, which cannot become the ground of an action.”
Later authorities dealing with the topic include Chasemore v Richards (1859), 7 HL Cas. 349, 11 E.R. 140, [1843-60] All ER 77; Mayor of Bradford v Pickles [1895] AC 587; Popplewell v Hodkinson (1869) LR 4 Ex 248; Langbrook Properties Ltd v Surrey County Council [1969] 1 WLR 161 and Stephens v Anglian Water Authority [1987] 1 WLR 1381.
Most of the authorities on this matter concern the activities of a landowner in drawing water from beneath his own property or mining on it, but the principle is equally applicable to any act undertaken solely beneath a person’s land (save with respect to running water) and which has the effect of desiccating neighbouring land. The roots of trees which remain wholly within their owner’s land may yet desiccate that of a neighbour. The principle remains. I can find no basis for distinguishing such a situation on the ground advanced by plaintiffs’ counsel, namely, that moisture diffusion was to be differentiated from the water percolations so frequently the subject of many of the decided cases.
It follows that if I am not satisfied that roots from trees and shrubs on the State’s land have crossed the plaintiffs’ property boundaries or that, having crossed, they caused no desiccation, then the rule in Acton v Blundell (supra) would deny the plaintiff a remedy in nuisance or negligence.
Pertinently, too, Langbrook, Stephens and Xuereb (supra) hold that just as no liability in nuisance can attach in such circumstances, nor can there be liability in negligence.
- Negligence
It is trite to say that in many cases where an adjoining owner has committed an act of nuisance, he may well also be liable in negligence. In Hargrave v Goldman (1963) 110 CLR 40, the defendant was a grazier who had discovered that lightning had struck a tree on his property and set it alight. He arranged for the tree to be felled, but did not subsequently put out the fire in it. In due course, it spread to his neighbours, causing loss. In the joint judgment of Taylor and Owen JJ, it was held that the defendant was liable in nuisance and negligence.
Their Honours referred to the dissenting observations of Scrutton LJ in Job Edwards Ltd v Birmingham Navigations [1924] 1 KB 341 (later approved in Sedleigh Denfield v O’Callaghan [1940] AC 880):
“There is a great deal to be said for the view that if a man finds a dangerous and artificial thing on his land, which he and those for whom he is responsible did not put there; if he knows that if left alone it will damage other persons; if by reasonable care he can render it harmless, as if by stamping on a fire just beginning from a trespasser’s match he can extinguish it; that then if he does nothing, he has ‘permitted it to continue’, and become responsible for it. This would base the liability on negligence, and not on the duty of insuring damage from a dangerous thing under Rylands v Fletcher ... I appreciate that to get negligence you must have a duty to be careful, but I think on principle that a landowner has a duty to take reasonable care not to allow his land to remain a receptacle for a thing which may, if not rendered harmless, cause damage to his neighbours.” (at 357/58)
Their Honours went on (at 53):
“But when the tree in question here was cut down a hazard of a different character was created and it is beyond doubt that the respondent was under a duty to use reasonable care to prevent it causing damage to his neighbours in the countryside. The finding that, in the circumstances prevailing, he failed to discharge this duty with the result that the appellants sustained the damage of which they complain is we think unassailable. We add that on this view it is of no consequence whether his liability rests in negligence or nuisance.” (my emphasis)
In the separate judgment of Windeyer J, his Honour found liability in negligence only and expressed reservations about the general concept of nuisance (at 61):
“The distinction between nuisance and negligence is not altogether clear cut. Until the recognition in modern times of negligence as a tort in itself, many actions of case which we would to-day say were based on negligence were described as being for nuisances ... The distinction between nuisance and negligence as separate torts may be of little, if any, importance for the ultimate decision of this case ...
“In nuisance liability is founded upon a state of affairs, created, adopted or continued by one person (otherwise than in the reasonable and convenient use by him of his own land) which, to a substantial degree, harms another person (an owner or occupier of land) in his enjoyment of his land.
“In negligence liability is founded upon the negligent conduct of one person causing, to any degree, foreseeable harm to the person or property of another person (not necessarily an owner or occupier of land) to whom a duty of care was owed.”
He then went on to discuss the notion of duty of care, found that the test of proximity did not assist him and ultimately fell back on what he considered the ordinary responsibility of an occupier of land “for consequences flowing from the state of his land and of happenings there ...” (p.66). At 67, he observed:
“To hold that the respondent had a duty to his neighbours to take reasonable care to prevent the fire on his land spreading would be in accordance with modern concepts of a land occupier’s obligations. If it be a new step in the march of the law – and I do not think that really it is – then it is not a step which we need hesitate to take if nothing stands in the way.”
That case, of course, concerned the occupier’s duty with respect to a burning tree trunk on his land and in today’s context, the duty is an obvious and well‑accepted one.
Does it bear comparison with the factual scenario asserted by the plaintiffs in this case, namely, the planting by the State on its own land, but adjacent to structures on the plaintiffs’ land, of trees and shrubs known to cause desiccation by tree root penetration beneath neighbouring land? Desiccation caused simply by bringing about migration of moisture from beneath neighbouring land will not be actionable under the Acton v Blundell principle, but does the situation become different if it is caused by “trespassing” or encroaching tree roots? In the words of Taylor and Owen JJ, do the adjacent plantings create “a hazard of a different character” and impose upon the State a “duty to use reasonable care to prevent [them] causing damage to [the] neighbour”?
These issues will arise as I discuss and make findings about the facts.
- Betterment
The issue of betterment is discussed in the authorities. In Murphy v Brown (1985) 1 NSWLR 131 at 133:
“Where a plaintiff claims the cost of the work necessary to put him or his property in the pre‑injury condition, the work must not merely be necessary for that purpose but ‘it must be a reasonable course to adopt’ to do that work: (Bellgrove v Eldridge (1954) 90 CLR 613). And, as the defendant’s argument here suggested, it will not normally be reasonable to spend, for example, $4,000 to restore a vehicle which, undamaged, was worth, say, $1,000.”
Such an outcome is not necessarily an unusual one (see Harbutt’s “Plasticine” Ltd v Wayne Tank and Pump Co. Ltd [1970] 1 QB 447 and Hoad, infra). In the latter case, Samuels JA observed, at 102:
“There may be a rule which requires a plaintiff to account for any advantage or betterment which he has obtained by repairing an old article with new materials, or by acquiring a new article for old in the case of replacement after total loss. Or there may be a rule which requires a plaintiff to bring to account, in reduction of his damages, any savings or profits which he has made by his use of the new article. There is undoubtedly a rule of the second kind which I will consider; but there is no rule of the first kind.”
Again, as the authorities illustrate, the determination must fall to be decided on having regard to the particular circumstances of the matter.
In Bellgrove (supra) the court observed (at 619):
“As to what remedial work is both ‘necessary’ and ‘reasonable’ in any particular case is a question of fact. But the question whether demolition and re-erection is a reasonable method of remedying defects does not arise when defective foundations seriously threaten the stability of a house and when the threat can be removed only by such a course. That work, in such circumstances, is obviously reasonable and in our opinion, may be undertaken at the expense of the builder.”
In Rentokil Pty Ltd v Channon (1990) 19 NSWLR 417, the court was faced with a factual situation similar to the present case. The subject property had been purchased in reliance upon a pest report that it was free of termites. In fact, it was so infested as to require demolition. The claim was based on negligent misstatement. The court reviewed general principles and at 429 Mahoney JA observed:
“In tort, the plaintiff is to be put in the position she would have been in if the tort – negligent statement – had not occurred. In the present context, this can more easily be done and it was, I think, this approach which essentially the learned judge adopted. But this ‘restitution’ approach is also subject to difficulty in particular circumstances. Sometimes it is impossible or not realistic to attempt, by money, to put the plaintiff in the position she was before she was injured because the circumstances have changed: see Murphy v Brown (supra). And sometimes the nature of the loss from which the plaintiff has suffered makes it difficult to calculate damages upon this basis.”
His Honour went on to observe that the rules relating to damages for economic loss arising from negligent misstatement contain special features applicable to that cause of action.
Meagher JA commented in that case, at 432:
“Within this general framework the law has developed subrules relating to the different torts, and sometimes within each tort differentiating torts affecting realty and torts affecting personalty. But it is important to remember that the various subrules are not inflexible, and if (sic) the application of any particular subrule may be disregarded if it would produce disconformity with the general principle. This is well illustrated by the decision of the House of Lords in Lodge Holes Colliery Co v Wednesbury Corporation [1908] AC 323. That was a case involving trespass to land, where the subrule provides that the proper measure of damages is the diminution in value of land (see Jones v Gooday (1841) 8 M & W 146; 151 ER 985); nonetheless, the House of Lords considered that the appropriate damages in the circumstances were the costs of reinstatement, a considerably higher figure, because the latter figure would be more in harmony with the purpose of the general principle of reinstating the plaintiff to the position he would have been in had the tort not been committed.”
- Mitigation
The question of mitigation was here raised and I adopt the test in British Westinghouse Electric and Manufacturing Company, Limited v Underground Electric Railways Company of London, Limited [1912] AC 673 at 689:
“The fundamental basis is thus compensation for pecuniary loss naturally flowing from the breach; but this first principle is qualified by a second, which imposes on a plaintiff the duty of taking all reasonable steps to mitigate the loss consequent on the breach, and debars him from claiming any part of the damage which is due to his neglect to take such steps ... this second principle does not impose on the plaintiff an obligation to take any step which a reasonable and prudent man would not ordinarily take in the course of his business.”
The question of whether a plaintiff has acted reasonably or unreasonably in not taking steps to mitigate is a question of fact (Payzu Ltd v Saunders [1919] 2 KB 581).
Although that was a contract case, the same test applies to damages claims in tort (c.f. Holmark Constructions Pty Ltd v Willis Faber Johnson & Higgins [1990] Aust. Torts Reports 81-029).
That authority was also considered in Hoad v Scone Motors Pty Ltd (1977) 1 NSWLR 88, where Samuels JA remarked at 100:
“But I think that the true rule is that a plaintiff need not risk his money too far, as he need not risk his person too far in the hands of surgeons.”
There is no need to further discuss that line of cases.
The onus with respect to mitigation lies on the defendant: “The plaintiff does not have to show that he has fulfilled his duty; the onus is on the defendant to show that he has not, and to show the extent to which he has not done so” (TCN Channel 9 v Hayden Enterprises Pty Ltd (1989) 16 NSWLR 130 at 158).
That onus is not easily discharged. In Banco de Portugal v Waterlow & Sons Ltd [1932] AC 452, Lord Macmillan said at 506:
“Where the sufferer from a breach of contract finds himself in consequence of that breach placed in a position of embarrassment the measures which he may be driven to adopt in order to extricate himself ought not to be weighed in nice scales at the instance of the party whose breach of contract has occasioned the difficulty. It is often easy after an emergency has passed to criticize the steps which have been taken to meet it, but such criticism does not come well from those who have themselves created the emergency. The law is satisfied if the party placed in a difficult situation by reason of the breach of a duty owed to him has acted reasonably in the adoption of remedial measures, and he will not be held disentitled to recover the cost of such measures merely because the party in breach can suggest that other measures less burdensome to him might have been taken.” (my emphasis)
- Delegable duty of care

Although the Further Amended Defence of the second defendant is not as specific as it might be about this matter, paragraph 2 appears to infer that the second defendant was not responsible for the design and planting of the vegetation because it delegated that duty to Land Systems Pty Ltd.
That matter was not much advanced in addresses, but it bears some consideration.
In Burnie Port Authority v General Jones Pty Ltd (1992-94) 179 CLR 520 at 550, the court spoke of those categories of case in which a duty to take reasonable care under the ordinary law of negligence is non‑delegable. It commented:
“In most, though conceivably not all, of such categories of case, the common ‘element in the relationship between the parties which generates [the] special responsibility or duty to see that care is taken’ is that ‘the person on whom [the duty] is imposed has undertaken the care, supervision or control of the person or property of another or is so placed in relation to that person or his property as to assume a particular responsibility for his or its safety, in circumstances where the person affected might reasonably expect that due care will be exercised’.
(The court was there quoting from Kondis v State Transport Authority (1984) 154 CLR at 687.) It went on (at 551):
“The relationship of proximity which exists, for the purposes of ordinary negligence, between a plaintiff and a defendant in circumstances which would prima facie attract the rule in Rylands v Fletcher is characterized by such a central element of control and by such special dependence and vulnerability.”
And at 552:
“It follows that the relationship of proximity which exists in the category of case into which Rylands v Fletcher circumstances fall contains the central element of control which generates, in other categories of case, a special ‘personal’ or ‘non-delegable’ duty of care under the ordinary law of negligence.”
I will not expand upon the reasons in that case, nor, indeed, comments with respect to it in Northern SandblastingPty Ltd v Harris (1997) Aust Torts Reports 81-435.
For reasons which will emerge, I am satisfied that this case falls within that category of case to which the rule in Rylands v Fletcher might formerly have applied.
ISSUES
1. The cause of desiccation beneath Nos 7 and 8
On the basis of the statement of agreed facts and the evidence of the geotechnical engineers, I find that desiccation of the soil beneath the structures at Nos 7 and 8 was caused by the migration of moisture from beneath them to the plantings. On all the evidence, this might have occurred in all or any of these ways:
1.1by direct transference of the moisture via tree and shrub roots penetrating beneath Nos 7 and 8 - the plaintiffs contended this, but the State argued it was not proven, Northern SandblastingPty Ltd v Harris (supra);
1.2by diffusion or natural migration of moisture from the wetter areas beneath those structures to areas south of the fence lines which had become desiccated because of the action of the root systems of those plantings operating within the linear park - the State argued this was the only relevant cause of desiccation; the plaintiffs did not dispute that this process may have contributed, but said the first or direct transference mechanism was the relevant one; and
1.3by direct movement of moisture southwards to the planted areas through cracks or fissures in desiccated soil – whilst this was recognised by all as a moisture transfer mechanism, it was not argued that it was a significant one in this particular case.
The dispute as to the occurrence or relevance of the first two of those causes has particular importance in the context of whether the State, by desiccating its own ground, merely deprived the plaintiffs’ land of support within the meaning of the rule in Acton v Blundell (supra) or whether, by actual root penetration, it committed an act of nuisance or neglect.
I will therefore discuss the question of root penetration.
2. Did roots from the plantings encroach upon either property?
The State contended that there was no good evidence that roots from the plantings had entered beneath either property and directly caused desiccation; alternatively, that the only evidence of root penetration was in an area of high moisture content and was thus not shown to be a cause of desiccation.
The State pointed to the following matters:
2.1the evidence of Dexter and others to the effect that the plant varieties used tended to have deeper tap roots and otherwise surface‑rooted systems and that they generally extended only as far as the canopy width or drip line;
2.2that the specified planting centres of 1.0 to 1.5 metres meant that no roots would likely penetrate under, or north of, either fence line;
2.3that the Woodburn borehole 1 showed fine tree roots in depths between 0.2 metres and 0.8, and what were more likely tap roots at depths of two to three metres, that borehole 2 indicated fine tree roots at depths of 0.2 to 1.2 metres and that both boreholes were amongst the plantings adjacent to No. 7; in other words, this was a typical root pattern for plants in that vicinity and there was little likelihood they had entered beneath either property;
2.4that borehole 9, beneath the house at No. 7, indicated fine tree roots at a depth of 1.5 to two metres but, significantly, too, there was a high soil moisture level and the soil suction factor was close to average. This indicated that the tree roots found at that location were not desiccating the local soil;
2.5there was no evidence of tree roots in Woodburn borehole 10, also taken under No. 7;
2.6there was thus no evidence that there were any significant root encroachments beneath No. 7 or, if there were, that they had had any desiccating effect;
2.7there were no boreholes drilled beneath No. 8, but I infer that the State was also contending that there was no evidence of tree root penetration beneath that land.
I have considered those submissions, but on all the evidence, I am satisfied that roots from the plantings did indeed penetrate the subsoil beneath each property and cause desiccation and subsidence of soil. I so find for these reasons:
(1)It is of no particular consequence whether or not I am satisfied there has been root penetration beneath the actual footings or superstructure of either building, indeed, as far as borehole 9: it is enough if I am satisfied that there has been root penetration beneath the surface of the land on which either No. 7 or No. 8 is situated and that that has had a desiccating effect.
(2)In the first place there is the early and very thorough investigation of Woodburn (P5). Whilst he does not comment specifically on the “trespass” of roots beneath Nos. 7 and 8, he plainly assumes that such has occurred and, indeed, that must be the context in which he discusses the possible installation of a deep cut‑off root barrier at the southern fence lines. That he has made that assumption is apparent, too, from his observations about the presence of tree roots in boreholes 5, 7 and 8 beneath No. 7 (as well as in borehole 9), where roots are found down to depths approaching one metre. Much the same observations are made with respect to borehole 12 at No. 8. Of those boreholes, it is significant to note that numbers 7 and 12 have high suction ratings at various depths, in other words, that desiccation is present.
(3)From the evidence of Mila and Liliana and, indeed, the photographs P20, P21 and P32, it is plain that the canopies of various plantings overhung the fences of Nos 7 and 8. Having regard to the expert evidence as to roots extending at least to the drip line of the plantings, the photographs (Exhibits P20, 21, 22, 31, 32 and 42) and the evidence showing that certain of the plantings were within one metre of the southern fence line of each property, there is an irresistible inference that roots from these plantings extended beneath the fence lines of each property, that is to say, they encroached.
(4)Goldfinch, in his report of 21 October 1998 (P4.47), observes:
“The photographs indicate that the offending trees and shrubs when first planted were most probably prolifically watered thereby satisfying the establishment of root systems in the year or two following their initial planting. In subsequent years the watering pattern ceased causing the tree/shrub roots to extend well into the properties at Nos. 7 and 8 ... in search of soil moisture.” (my emphasis)
(5)In his report of 17 December 1997, Mitchell observes:
“It is estimated that prior to the effects of trees at the site, the area around and under the house was in a wet condition, from the influence of lawns and plumbing leaks. This created a situation attractive to the roots in their search for subsoil moisture, and the resulting magnitude of subsoil moisture loss from the trees is greater than if the original moisture condition was drier.” (my emphasis)
Elsewhere, in his evidence (p.374), Mitchell suggested that lateral root systems of Australian natives can extend up to four metres.
(6)None of the experts suggested in evidence that there had been no encroachment of tree roots beneath one or other property and, indeed, all appeared to assume that that process had occurred. They spoke of the attractiveness of the wetter‑than‑normal conditions usually prevailing under concrete paving, in particular that paving adjacent to the southern fences.
(7)Borehole 2, shown as very dry, is 0.5 metres south of the southern fence whereas the wetter borehole 9 is some 2.5 metres north of it – this of itself supports the likelihood of root penetration beyond the fence line.
3. When did such encroachment likely occur?
I am mindful of the above quoted remarks of Goldfinch, to the effect that cessation of watering by the State was the likely cause of the tree roots searching beneath the adjoining properties for other moisture sources.
The evidence as to when watering of the plantations by the State actually ceased was sparse. Dexter had thought that it was to last no longer than three months, but he believed that it might in fact have continued for six to twelve months. No other evidence was called by the State as to this matter and the only evidence from the plaintiffs was to the effect that there was a period of intense watering after the garden was first planted, so much so that it resulted in flooding of the pathways of No. 8. Just when that watering ceased was, however, not clear. The effect of the evidence of Mila and Dexter is that it likely carried on from the time of planting for at least twelve months.
The linear park was, of course, transferred to the Council in July 1991, some two or three years after the plantings.
It was nearly five years later that the photographs P20, P21 and P32 were taken and Woodburn first reported on the presence of tree roots beneath both properties.
I have already found that, by the time of the first Woodburn report (February 1996), root encroachment beneath Nos 7 and 8 had occurred.
On the basis of the evidence, however, I am not satisfied it has been shown that there was any encroachment of tree roots from the plantings into the subsoil beneath either Nos 7 or 8 at any time when the State was the owner of the linear park.
Given that finding, I am not satisfied any claim in nuisance has been made out, that is to say, that the State has been responsible for any nuisance, in the form of encroaching tree roots, at any time when it was the adjoining owner.
Further, it must follow from my observations on the law, that the plaintiffs cannot succeed in nuisance simply because the State has, by desiccating its own land, being the area beneath the plantings, caused migration of moisture from beneath Nos 7 and 8 and resulting soil subsidence and property damage (Acton v Blundell; Xuereb v Viola, supra).
4. Which mechanism was the cause of the desiccation beneath Nos 7 and 8?
My finding as to the presence of roots beneath Nos 7 and 8 and their desiccating effects does not preclude the possibility that desiccation was also contributed to by natural migration.
I am satisfied, however, that tree root penetration was the effective or commonsense cause of the desiccation beneath Nos 7 and 8, in the sense that term is used in March v Stramare (1991) 171 CLR 506. As was observed in that case, the “but for” test of causation can be a useful tool in eliminating other causes and indeed, here, I can say I am satisfied that but for the penetration of tree roots that I have found occurred, the significant desiccation discovered in and after 1995 would not have occurred. Put another way, I am not persuaded, on the evidence, that simple moisture diffusion due to desiccation beneath the plantings would have caused that desiccation and resulting distress.
I so find for the reasons that:
(1)Woodburn commented on the structure and paving of each property and observed that (in their constructed states) both had “been reasonably well protected from local soil moisture changes occurring adjacent to their footing systems”. He recommended steps to remove the effect of the roots by installing barriers or removing the plantings, commenting that the situation could worsen as “the trees search for moisture”.
He accepted that natural diffusion would occur from a wet to a dry zone and even allowed that there might not be a significant root invasion beneath the house structure itself, but said it was “very likely there are tree roots under the concrete paving adjacent to the house ... we get a store of moisture under the paving during the wetter months ...” (p.287) “… so the zone of intense drying can be I would think as far as that concrete path and then diffusion of moisture from under the house into that dry zone” (p.288).
I am thus satisfied that he regarded the presence of tree roots, particularly beneath the house paving, as the primary cause of the footing subsidence.
(2)Goldfinch at the outset attributed the damage principally to “tree root clay soil shrinkage” (P9), not to some process of diffusion, and his opinion as to that did not waver. He expanded on that (pp187/88) and on the significance of paving at transcript p.222.
(3)Mitchell accepted the plantings had caused the problem. He did not argue that roots had not penetrated beneath either property and, indeed, quoted from his own publication as follows:
“These lateral root systems are considered to primarily affect a footing of a structure, as they extend a considerable distance from the trunk, and extract moisture from within the zone of soil supporting the footing.
It is generally accepted that the lateral root systems of an individual tree can affect a structure if it is located within a distance from the tree less than its height (and at greater distance with groups of trees).
It appears that more drought resistant is the tree (such as Australian natives) then shallower is its roots system in order to collect the random and light rain that does fall in these more arid areas.
…
All measurements that have been taken reveal the extremely large amount of water that is taken from the soil by tree roots and used in transpiration. For example, at a moderate transpiration rate, a tree of moderate size (say 4m high) will have an uptake of approximately 100 litres/day.”
He went on in that report and in his evidence to set out and discuss some calculations as to likely moisture diffusion from beneath the properties and soil settlement “even if the roots do not extend beyond the vegetated area”. I was not much assisted by that evidence, and for these reasons:
(a)I have found that roots from the plantings did in fact enter into the subsoil of Nos 7 and 8 and that finding is, indeed, consistent with his own observations as to likely root spread;
(b)his calculations were necessarily based on an assumption of an homogenous subsoil and there was no evidence of that; indeed, all evidence was to the effect that this particular soil type was highly variable and over short distances;
(c)in any event, Mitchell readily conceded that diffusion, even in that idealised situation, could not account for more than 25 per cent of the observed movement;
(d)Woodburn and Goldfinch did not attribute much weight to those calculations, considering they were based on idealised and unproven soil conditions.
(4)Of particular significance is the time when the real distress was first observed, that is, late 1995. The plantings had not been artificially watered for between four and six years prior to then, yet the likely level of natural diffusion had not, till then, caused distress.
On the expert and other evidence, I am satisfied that tree and shrub roots gradually penetrated the plaintiffs’ properties in search of moisture over that time and that it was their presence which desiccated the subsoil beneath each property, particularly beneath the southern paving of each, such that moisture was extracted directly by the roots or otherwise migrated from beneath the respective houses and house footings to replace it.
5. Did the desiccation cause structural damage to either property?
With respect to this matter, on the basis of the evidence and agreed facts, I am satisfied and find that desiccation did, indeed, cause shrinkage of subsoil beneath the footings of each property, particularly in the south‑western corner of each, and that there was resultant settling of the footings in those areas, resulting in the distortion of their respective footing systems and consequential structural damage to the buildings.
Both Woodburn and Goldfinch were of that firm opinion.
Mitchell at first thought it was the most prominent cause (“at least 80 per cent” – D1.219), but that sewer leakages might also have contributed to the distortion. His first opinion was expressed at a time when he was unaware that remedial measures, in the form of artificial irrigation, had been installed which had increased moisture levels in the subsoil. Later, having learned of those measures, he became less interested in the potential role of a sewer leak and seemed prepared to accept that the effective cause of the distress was desiccation caused by the tree and shrub plantings (see transcript p.445).
Indeed, it became common ground and an agreed fact that desiccation by the plantings caused the structural damage.
6. The state of No. 7 prior to tree and shrub planting
On the unchallenged evidence of Liliana, I accept there was a dilapidation inspection of her property carried out by three or four personnel from the Project prior to works being commenced. At that time, there was a tenant in the place and she did not go through the house with them, nor did she subsequently receive a copy of any report. Indeed, for reasons which never emerged, no such report was produced by the State at trial. In a later engineering report of 28 March 1998, prepared for the State with respect to No. 8, the author, Mr Sandery, did, however, comment:
“The dwelling at No. 7 Kevin Road was also inspected and there was little change from the December 1986 inspection.”
On Liliana’s account, there were then no cracks or obvious signs of movement in her property, nor were there as of 1992 when she agreed to let the house to a tenant named Brewer. She referred to an agreement and inspection sheet (P11 and P12) relating to that tenancy and pointed out that there are no references in either document to cracking, nor did Brewer say anything to her about cracking until it came to the end of her tenancy in about May 1995. Brewer then said that there was cracking present in the bathroom. She did not immediately inspect it, but did so after Brewer left in November 1995. She saw what she called “major or bad cracking” in the bathroom and also near the front entrance and lounge room/passageway door. At about this time, too, her parents had become aware of serious cracking at No. 8. Liliana first spoke to a builder about the problem and then wrote to the State on 28 November 1995 (P13), complaining about it.

In cross‑examination, she was tested about her letting out the property between 1981 and 1995. She said that prior to Brewer, there had been three or four tenants and after each left, she would go in and repaint and clean up the house. On those occasions, she saw nothing resembling the cracks that appeared in 1995. She said there might have been “hairline” cracks (p.91); she could not actually remember seeing any, but did not dispute there might have been some. If present, they would then have been filled and painted over prior to the new tenancy.
Liliana’s evidence with respect to the above matters is not inconsistent with the evidence of any of the consulting engineers. Each of them thought that, having regard to the soil conditions and the footing type likely to have been constructed at No. 7 (there was no evidence available as to its precise dimensions), it was likely that the structure would have undergone some cracking over the period after it was built, albeit that such may not necessarily have been anything more than hairline cracking.
Elsewhere there was evidence from the experts and a CSIRO publication (P36) about terminology commonly used by engineers and in the building industry to describe types of cracking in masonry walls:
.a category 0 crack, described as “negligible” or “hairline”, is defined as one of a width of less than 0.1 millimetre;
.a category 1 crack, (less than 1.0 millimetre) is described as “very slight” and one which can easily be treated during normal decoration. It is rarely visible in external brickwork;
.a category 2 crack is one less than five millimetres in width and is a “slight” internal crack which is easily filled. Redecoration is probably required, but recurrent cracks can be masked by suitable linings and are not necessarily visible externally. They may cause sticking of doors and windows;
.category 3 cracks, described as “moderate”, are between five and 15 millimetres in width and can be repaired. Sometimes a small amount of brickwork may need to be replaced. Doors and windows stick, service pipes may fracture and weather tightness can be impaired;
.a category 4 crack is described as “severe”. It is 15 to 25 millimetres and requires extensive repair work, breaking out and replacing sections of walls, especially over doors and windows, distortion of door and window frames, floors sloping, walls leaning or bulging noticeably, some loss of bearing in beams and service pipes disrupted;
.a category 5 crack, described as “very severe”, is usually greater than 25 millimetres, depending on the number of other cracks, and requires a major repair job involving partial or complete rebuilding. Beams tend to lose bearings, walls lean badly and require shoring, windows are broken with distortion and there is a danger of instability.
On the evidence of Liliana and that of each of the consulting engineers, I am satisfied and find that prior to the time when the Brewer tenancy commenced in May 1992, No.7 was suffering from either no cracking or no more than category 0 cracking, that is to say, negligible or hairline cracking.
7. The state of No. 8 prior to the planting
A dilapidation report was undertaken with respect to No. 8 in January 1982. This report was available and became Exhibit D6. I will not repeat its contents, but it described the property, inter alia, as a:
“Well built dwelling on substantial footings and in good condition, well maintained internally and externally.
Internally there is generally cracking at ceiling due to seasonal change, with minor cracks over some doors and windows.
Externally a settlement crack is evident adjoining the dining room window with minor cracking to rendering to footing and movement of concrete and other paving away from building.
No evidence of cracking or movement was visible to the garage or the lean to structure at the rear of the property.”
Plainly, the author of that report does not seek to categorise the observed cracks in the formal way I have just described and, indeed, the only qualifying terms are “fine” or “minor”. Pertinently, there is an observation relating to the kitchen of “Vertical crack over E. side of window. Fine horizontal crack 100 below head of door on E. side. Crack in ceiling from window to fan and fan to E. Wall”. In the hall, there is the observation: “Fine vertical crack N. side of door, fine vertical and horizontal cracks at door heads”. Then there is the reference to the shed “with masonry wall on eastern side and hotmix floor. No sign of cracks in masonry wall, but cracks were visible in bitumen.” A legend to that plan describes a “three vehicle masonry built garage with Brownbuilt galv iron roof and 3 roll up doors, concrete floor, skillion roof storage shed one side filled in with masonry wall. Hot mix floor.”
On all the evidence, it appears that this garage was part of a continuous shed structure which was later extended in 1983.
I have already described the circumstances in which the further inspection of 10 December 1986 occurred. It appears to have been undertaken by an engineer and speaks, inter alia, of “Fine crack above LHS front door”, “Crack to corner of cornices above timber panelling” at entry and “Crack above LH window” in kitchen: it does not purport to formally categorise that cracking in the terms I have set out above. With respect to the “Large S/B garage/workshop at rear”, it comments, “Vertical crack on rear centre corner of walls”. It then refers to photographs, but none were in fact produced.
There is then the further inspection report of 28 March 1998, prepared in circumstances I have already described and, again, by an engineer. It comments:
“Since the original inspection quite substantial cracking has occurred in part of the house. Observation of the pattern and position of cracking indicates that the centre of the house (along a N-S axis) is displaced upward relative to the front and rear of the house ... the magnitude and location of the problem indicates that normal seasonal soil movement would probably not have caused the problem ... The cracks in the garage/workshop at the rear are slightly larger than at the previous inspection, but there is a large eucalypt immediately alongside the workshop, and this would have considerable effect on the footings.”
The author goes on to observe that the major cracking appears to be in the area of the en suite bathroom and potentially implicates a leaking drain. He does not consider that vibrating compaction equipment has likely caused the problems, nor has lowering of the watertable in the excavated area to the south of the house. He concludes that sewer leaks are the likely cause.
It should be kept in mind, here, that there is no en suite bathroom immediately adjacent to the southern wall of the premises at No. 8.
In her evidence, Mila first spoke of observing the crack above the front entrance door opening slowly in late 1995. By this time, Liliana had called for assistance with respect to her property and Mila then had the engineer also inspect theirs. Prior to then, there had been “very hard hairline bricks (sic) but we didn’t pay no attention, it is just when completely the bricks crack and start opening, then I was worried” (p.122). She then spoke of other areas where she noticed movement in her house and, in particular, of the lounge room, dining room and the back of the garage. She was asked (at 123):
“Q.Prior to that episode where you started noticing all the cracks that you’ve told the court about, had you had any problems with cracking or movement in that house.
A.No.”
In cross‑examination, Mila was reluctant to concede the accuracy of the observations in the Exhibit D6 relating to the dilapidation inspection of 21 January 1992, and said that she and her husband had not been involved by the inspectors in that assessment. In fact, she rejected the conclusions expressed in that report.
She did, however, agree with the observations in the inspection report of 10 December 1986 (D7), and said that at the time the engineer then visited them, he told her the damage was cosmetic and could be painted over. She went on to say that the crack at the rear of the garage that was commented upon then by the engineer was not as it appears now. It is now worse.
She was then shown the inspection report of Sandery of 28 March 1988 (D9). Notwithstanding that the correspondence suggested that it had been forwarded to her, she denied she had in fact ever received it and said she had only had the chance to read it in the last few weeks. With respect to it, she agreed that there was at the relevant time a large eucalypt situated at the south of the garage and, indeed, that was the specimen planted by the Premier.
It was then put to Mila that on the basis of the observations in the three reports, she had had more than simply cosmetic cracking to her property as of the plantings. She did not agree with that, nor with the assessments made in Exhibit D6, nor with the assessments in D7 or D9. Her evidence as to this was perverse in two respects:
(1) because she had elsewhere accepted that there was some measure of cracking in the house prior to 1988; and
(2) because she had previously accepted some of the propositions put to her about the conclusions in the exhibit D7.
It was not, however, perverse to the extent that she denied the cracking was worse than cosmetic. The basis for that particular challenge was a poor one: none of the reporters had sought to use the accepted cracking or category descriptions and the use in the cross‑examination of a lay witness of a further description (“cosmetic”) was unhelpful.
She was then shown the report of B C Tonkin & Associates (P38). She agreed that it had been obtained by her solicitors in about July 1988. She agreed that it appeared to refer to the document D9, thus implying that she or her solicitors had had possession of D9, but she still maintained that she had not herself previously seen D9.
As to the irrigation works recommended by Goldfinch, she had continued with them until after the further boreholes were drilled by Goldfinch. She agreed by reference to documents that those boreholes had been drilled in August 1999 and she believed she had therefore stopped irrigating outside both properties between August and October of 1999. Otherwise, she had continued to apply water to the boreholes at the front of No. 8 until the present time. Even so, when it was very hot she would water outside the southern fences of both properties, anyway.
She was then asked about a site visit in October 1996 by Mr Whitehill and another person. She said they had come there from the Botanic Gardens after the plantings had been cut back. She had shown them around both properties and had pointed out the shoots that were sprouting away from the plantings. Whitehill pulled some out and told her to pull them out as they appeared. When it was put to her that Whitehill did not attend until after the stumps had been grubbed out, she said that in that case the person who came before then might not have been called Whitehill, but in any event, a man had come along with a boy of about 16. The man had not introduced himself or given her any identification. He had just said he was from the Botanic Gardens and that he had come to identify plants.
In re-examination, she said she did not know his name, but he came with a boy and said he was sent there by the transport people. He was tall and elderly, with a big hat. He only came once. Many other people have come and inspected the site, but he was the only man that came and spoke to her about the plantings.
She was then brought back to the inspection reports D6, D7 and D9 and said she had received compensation for painting her house of $600 and, as well, for concrete and for legal expenses.
Further in re-examination, she said that the larger garage abutting the southern fence line of No. 8 was a workshop and had been built in 1983.
The Tonkin report (P38) is mildly critical of the report D9 for not mentioning cracking in the dining room and a change in the slope of the concrete path to the south of the house. It also comments on the owners’ objections to the suggestion that there was a water or sewer leak present. It goes on to say that even if such a leak were present, it would not account for the crack in the lounge room or the southern external wall. Helpfully, it adopts the cracking categorisation of the CSIRO document and observes that the largest crack in No. 8 would be a category 1, with the remaining cracks ranging down to category 0. The author appears to regard that cracking as having been caused by the vibrating roller works, but believes it can be repaired in the normal course of maintenance. He is, however, more concerned about the reverse slope on the southern concrete path and suggests it should be repaved.
Plainly, the author’s observations as to tree plantings were conveyed to the State, as the correspondence (in particular, P37) shows. The report is also interesting in that it must be inferred from its timing that no plantings had in fact occurred as of July 1988.
Overall, though, the combined effect of Exhibits D6, D7, D9 and P38 is to affirm, and I find, that there was, indeed, cracking to No. 8 up to and as at July 1988, but that it was no more serious than “negligible” or “very slight” (categories 0 and 1).
As I have commented, Mila seemed to challenge the accuracy of some or all of the observations as to cracking in D6, D7 and D9 and yet seemed prepared to accept the assessments in P38. I do not consider that this reflected seriously upon her credit. She seemed to me to be quite upset about not having received copies of certain of those reports (whether or not her solicitors had), about the reporters’ descriptive terminology and about their opinions as to causation.
Plainly, from at least 1982, she had observed that there was what she called “hairline” cracking in her property, but it had not concerned her. In light of the later inspections and reports, about which she knew (whether or not she read them), including that of her own engineer, Mr Tonkin, I did not regard her as attempting to deny that there had been some level of cracking present in her property, as, indeed, I am satisfied there was.
If I am wrong in that and if it were considered that her denials impacted upon her credibility, I should say there was no other area of her evidence where I felt the need to rely upon her evidence alone. I have otherwise found that the state of No. 8 was as described in those reports up to and including July 1988 and I am most assisted in that by P38 because it is the only report that adopts a recognised cracking categorisation.
Further to that, there is abundant evidence, which I will deal with in due course, indicating that the state of that cracking, in certain parts of No. 8, deteriorated after the plantings.
8. The consequences of desiccation for No. 7
Proper discussion of this issue obliges me to expand upon the history of engineering inspections and advice.
The first engineer to inspect No. 7 after Liliana’s complaint of late 1995 was Woodburn in February 1996 (P5). He was commissioned by the State to carry out an inspection, he did so and reported that there was substantial settlement and distortion of the footings on the southern and western sides, more particularly towards the south‑western corner. Relative to the highest point at the north‑east corner of bedroom 1, there was a fall to the south‑west corner of 135 mm. He described extensive internal cracking, some cracks opening to “nearly 20 mm close to the ceiling” and predominantly occurring in the north‑south walls and over doors and windows. He commented that the damage to the property was “severe and its stabilisation and restoration to close to its original condition will be difficult”.
That report was not, however, provided to Liliana and, after some further correspondence, she instructed solicitors and subsequently, with her parents, engaged Goldfinch to inspect both properties. At the time of writing his first report, Goldfinch did not have access to Woodburn’s original site observations and testing, but pertinently commented:
“At this very early stage of our investigation the pattern of cracking and obvious slope across the floors indicates that these dwellings are suffering from footing settlements which have been induced principally by tree root clay soil shrinkage …
If the offending trees are removed prior to the completion of winter rainfall then there is a reasonably good prospect of the current cracking stabilising and possibly closing up as the soil absorbs the winter rains.”
Eventually, he obtained the Woodburn report and agreed with its substance, recommending tree and shrub removal as “a matter of considerable urgency”, which should be “followed immediately by re‑wetting of foundation soil” (report of 14 November 1996). The latter measure he saw as a maintenance problem and he suggested the best long‑term and permanent solution would be underpinning.
There was a good deal of correspondence between the plaintiffs, the Council and the Crown Solicitor, to which I have already adverted, but, notwithstanding the opinions of Woodburn and Goldfinch, the trees were not removed. In consequence, the plaintiffs sought and obtained against the Council a court order directing the removal of the plantings. That work appears to have begun on 1 October 1996 (Exhibit P21 and the evidence) and all the vegetation was cut back to stumps by the end of that month (Exhibit P22).
On Liliana’s evidence, supported as it is by the photographs, it is plain that this measure did not kill the plantings and they began to sprout from the stumps and, as well, shoots appeared in her lawn. They seemed to her to be shoots from the shrubs and she pointed to two of them in the Exhibit P22. In the meantime, she said, internal cracking in her house was continuing to widen. In consequence, she approached her solicitor to obtain a court order for the stumps to be grubbed out. Her solicitors’ response to this led to further discussions and, as I have noted, a meeting of all interested parties, including the State, at the site on 29 January 1997.
It is a matter of considerable significance that all parties then agreed that the following rectification steps would be taken with respect to both Nos. 7 and 8, namely:
(1)removal of all vegetation and shallow roots adjacent to the southern boundaries;
(2)mulching of those areas;
(3)installation of a dripper irrigation line 300 millimetres south of the fence and beneath the mulch and feeding water into that line at a prescribed rate;
(4)the Council to pay $100 to the owners for water and provide materials for the watering system;
(5)the eucalypt tree planted to the south of the garage in No. 8 be removed and replaced with new, smaller shrubs.
The Council duly complied with its undertakings and, for their part, the plaintiffs installed the irrigation systems. They connected them to their own water supplies and Mila then undertook the task of feeding the drip lines to each property three times a day (or more often if it was a hot day). At that stage, there was no set period fixed for the continuation of watering and it was ultimately to continue until Goldfinch recommended its cessation, nearly three years later, in late 1999.
Over that time, as the rewetting proceeded, the cracking in No. 7 and, indeed, No. 8, was seen to partially close up. Liliana then noticed that doming of the centre floors of the affected rooms of No. 7 was taking place. Previously, they had simply sloped downwards.
It was soon after this time that Mitchell conducted his first inspection of the property and prepared his initial report. For reasons which did not emerge, he had not been provided with a copy of the Goldfinch report of 4 February 1997, nor, indeed, with any details of the agreement concluded between the parties with respect to artificial irrigation adjacent to the southern fences of each property. He conducted his own levels survey and noted that, as of November 1997 and, indeed:
“… since removal of the shrubs from neighbouring property in October 1996, the magnitude of tilt in the structure has reduced. If nothing was done at all, the present rate of recovery would indicate that any effects of the trees will have been overcome in three years time. This recovery is proceeding because of natural soil moisture recharge as a result of removal of the shrubs, leading to a footing heave.” (my emphasis)
He observed the doming and found it surprising, but considered it was consistent with subsoil wetting, which he then sought to attribute to leaking pipes. Even so, he then thought that the trees had contributed to 80 per cent of the footing distress and damage.

For all the above reasons, I am satisfied and find that the adoption by the plaintiffs of the Goldfinch/John rewetting method was both appropriate and reasonable and that it achieved a return of moisture to the subsoil beneath each structure to the best levels reasonably obtainable. Further, I am satisfied that the artificial introduction of further moisture beneath No. 7 will not likely improve the current level of footing displacement.
Even if I am wrong in that, I am satisfied that at least until July 2002, the State expressly and/or impliedly conceded that it was an appropriate rectification measure.
For all these reasons, and adopting the legal principles referred to elsewhere in these reasons, the plea in mitigation, upon which the defendant bears the onus, must fail.
On all the evidence, it follows and I am satisfied that each of the structures on Nos 7 and 8 have, through the removal of trees, natural watering and the introduction of the Goldfinch/John watering system, been returned, in terms of footing settlement and consequential cracking, to a point beyond which there is unlikely to be any further substantial improvement, without mechanical intervention.
11. Remediation – No. 8
With respect to No. 8, Goldfinch initially recommended underpinning and then repairs, whereas Mitchell took the view that underpinning was not necessary and that cosmetic repair would suffice. Woodburn did not think underpinning was necessary and Goldfinch ultimately conceded that if the previous cracking at No. 8 was as described in D6, D7 and D9, then underpinning might not be necessary.
I have already found myself satisfied that the prior state of No. 8 was as described in D6, D7 and D9 and, on all the evidence, I am satisfied that underpinning those premises is not necessary. They can be repaired by plastering and painting.
12. Remediation – No. 7
The position concerning No. 7 is more contentious.
Having found that the moisture content of the subsoil beneath No. 7 has been returned to a state of relative stability and that any further substantial improvement in the distortion of its footings is unlikely to be obtained, I am satisfied the structure is left with a permanent level of distortion in terms of a planar tilt towards its south‑western corner, such that the level falls away to that corner from the highest footing point by 99 millimetres.
The Goldfinch proposal involved artificially correcting that displacement by jacking up the footings to a level state and fixing them in place by underpins. At that point, he said, the structure would be stable and packing and repairs could then be completed.
That specification gave rise to the following considerations:
(1)Where there is cracking in the footings, underpins may be required on either side of the crack.
Goldfinch said, in response, that in obtaining the underpinning estimate, he had allowed for the likely cracking sites and, as well, for the need to double up on underpins or otherwise space them closer together. He conceded in evidence that the cost of underpinning could conceivably reach a point where it became uneconomic compared with the cost of demolition and rebuilding, but he was confident that the quotation he had obtained from the contractor Palmer was based on what he considered to be a worst case scenario.
Put another way, as I understood him, he was saying that it was not likely that underpinning costs would exceed the provision made for them in the Palmer quotation.
(2)Inherent in underpinning is that the footing beams will be lifted above the soil profile. Goldfinch was confident that with the underpins, they would support the structure and that there would be no further swelling of the soil, so there was no reason to anticipate any problems of heaving.
(3)Goldfinch conceded that underpinning would “provide a far more stable footing system than existed before the trees were planted” (p.344).
(4)Woodburn supported the Goldfinch opinion that underpinning was the only way to correct and support the deformation, but again cautioned that the cost would depend on the number of fractures in the footings. Otherwise, he pointed out, if the building were left underpinned, it would not only be 100 millimetres out of level, but would remain subject to seasonal influences on the moisture content of the subsoil and would need careful monitoring and professional supervision.
(5)I have already rejected Mitchell’s opinion that further substantial recovery of footing displacement is achievable by moisture injection.
Nonetheless, he was of the view that even if the displacement differential remained at 100 millimetres, it would be possible to repair the structure in that state and thus leave it in much the same position as it was prior to the plantings. He was tested at length about this and about the cost of works required to correct internal floor and ceiling displacements of 100 millimetres extending over the distance from the north‑east corner of bedroom 1. His plan, he said, did not involve correcting the tilt. He said that it would not be aesthetically necessary to correct it if it were a 50‑millimetre drop, but on being tested as to a 100‑millimetre fall, he seemed less sure about the aesthetic implications.
Further to that, he expressed misgivings about the capacity of the footings to operate as beams, once lifted clear of the supporting foundation by underpiering, and commented that there would need to be sufficient piers to provide that support.
Otherwise, he said, his simple repair regime did not envisage any specialised maintenance program beyond ordinary matters such as avoiding pipe leakages, the planting of vegetation, house paving and the like.
(6)One point of dissension at trial, was whether the footings beneath No. 7 had actually failed due to “yielding” of the steel reinforcement within it. Goldfinch was of the opinion that this was quite likely, but in that he was not supported by Woodburn, nor by Mitchell. In the lack of any specific evidence on the matter, I am not prepared to find that the steel reinforcement had, indeed, yielded or failed, but I do not regard that finding as necessarily impacting upon the capacity of the fractured footings to act as beams, if they are properly supported by underpins.
Those, then, were the remediation issues.
Both Goldfinch and Woodburn were of the view that, even allowing for proper maintenance, if the structure were repaired by the Mitchell method, it would remain liable to distress from variable seasonal factors. Mitchell disputed this and said it would be in no more vulnerable a position than it had been prior to the plantings.
On the general issue, I preferred the evidence of Goldfinch and Woodburn over that of Mitchell, for these reasons:
(a)Even as a lay person, it does not appear to me to be apt to compare or predict the likely behaviour under ordinary seasonal conditions of a properly maintained house with hairline cracking, to the behaviour of a house with very severe cracking and known to have a planar footing displacement of 100 millimetres, particularly in circumstances where the soil profile is known to be variable, even over short distances. The Mitchell proposal envisages that the current structure will “float” on the unstable soil in much the same way as it had prior to the plantings, yet on all the evidence, it is now a somewhat different vessel.
(b)There seems to me to be no good reason why the owner of No. 7 should be expected to resume living in or tenanting a property containing such a marked internal tilt, however the cracking might be repaired. In effect, the State is saying the claimant should accept a property, properly repaired, but with a permanent and substantial tilt which has aesthetic and perhaps utilitarian considerations. Mitchell was even hesitant about that.
(c)I am satisfied that Goldfinch has made a fair estimate of the likely amount of piering required under No. 7 and that the repair quote is based upon that.
(d)I am further satisfied, on the basis of Goldfinch’s evidence, that that estimate ensures that the raised sections of footing will adequately support the structure and not likely be subject to soil heave.
In the end, the issue seems to amount to this: the Goldfinch proposal probably confers on the footing structure, more stability than it had even prior to the plantings – the State queries why it should have to compensate the owner for the cost of improving the structural quality of her house – whereas the Mitchell proposal involves repairing the house to its pre‑planting status, but leaving it with a deficit it did not previously have, namely, that 100‑millimetre level of displacement. Put shortly, the Goldfinch one restores the third plaintiff to a better position than she occupied prior to the plantings, whereas the Mitchell one does not quite bring her to that point.
The other solution discussed, and agreed by all the experts to be unnecessary, was that of demolition and rebuilding an equivalent structure, but even then rebuilding would require the installation of a better or “state of the art” footing and to that extent improve the third plaintiff’s position.
I have discussed the authorities as to betterment, elsewhere.
Here, I am persuaded that ordinary principles of reinstatement require that the third plaintiff should have the benefit of a repair that puts her in a better position than she previously occupied rather than the detriment of one which would not restore her to her pre‑injury status. If there is no solution which restores her precisely to that status, and there was no evidence placed before me of such, then the second defendant must bear the higher cost because it is “more in harmony with the purpose of the general principle of reinstate(ment)” (Rentokil, supra).
CONCLUSIONS
I have already found that it was not proved to my satisfaction that any roots from the trees planted by the State to the south of either property, entered into or beneath either No. 7 or 8 at any time prior to the transfer of the linear park to the Council in July 1991. For reasons expressed, the plaintiffs’ claims in nuisance must therefore fail.
I am otherwise satisfied on the evidence that at some time after July 1991 but prior to late 1995, roots from the trees and shrubs in the plantings did penetrate the subsoil beneath Nos 7 and 8 and did themselves cause the desiccation there which led to settlement and structural damage to both houses.
The question then arises whether the State was negligent in planting those specimens.
There was undoubtedly a relationship of proximity or neighbourhood between the State and the plaintiffs – that could hardly be doubted – and the State thus fell under a duty to take reasonable care in planting them to avoid foreseeable risk of injury to the plaintiffs.
In the context of that duty, I make the following observations and findings.
On the evidence of both Mitchell and Goldfinch, trees have been identified in Australia, as a source of damage to structures, from the 1950s and the risk they pose is known to be exacerbated if they are fast‑growing trees and/or in periods of dry weather, when they demand more water than is available from rainfall and with respect to particular native varieties.
An early approach to this problem by geotechnical engineers, was to limit the planting of vegetation close to structures, but they found that this conflicted with the requirements of others, such as gardeners and landscape architects.
Mitchell commented that non‑engineers were slow to accept the significance of trees in causing structural distress, and even the Adelaide Botanic Gardens sought to warn about these risks for heavy, as opposed to “light” structures, as late as 1986.
Mitchell went on (D1, p.220), however, that:
“By the mid-1980’s then, there was general acceptance by non‑engineers of the potentially damaging effects of trees on houses ... there was much slower recognition by the geotechnical engineering community of the severity of damage associated with native Australian species compared to damage induced by introduced species.”
He then referred to a November 1981 publication identifying evergreen Australian trees as causing most problems and went on to say that by the mid‑1980s, the CSIRO, the Institution of Engineers, and the institutes of architects and landscape architects had accepted:
“... that trees, and in particular in Adelaide, some native species, have a high potential for affecting nearby housing.
The writer would conclude that by the mid‑1980’s there was widespread knowledge of the potentially damaging effects of some native species on buildings ... it would have been widespread knowledge by the mid‑1980’s that any tree or shrub has a potential to affect a house to some degree depending upon its distance from the house and the soil type.” (my emphasis)
Both witnesses referred to various learned articles on the topic and, indeed, some of them were tendered, but I will not dwell upon them now.
Goldfinch observed (P9, 21.10.98 at 1.5):
“State and Federal government agencies ought to have known about the harmful effects of tree roots on structures in the early 1980’s within the period 1980-85.”
Mitchell, at D1.231 said he generally agreed with Goldfinch’s observations as to this.
Finally, there is the agreed fact number 4 that it was well known at the relevant time that the planting of trees, particularly Australian natives, in clay soils might result in desiccation.
On the basis of that evidence, the warning in the Tonkin report (P38) and the agreed facts, I am satisfied that by 1988 the second defendant, as a State government, either knew or ought to have known of the risk posed in planting native species of trees or shrubs in the linear park in positions too close to nearby structures, in particular, here, those at Nos 7 and 8 Kevin Road, the more so in circumstances where it was aware, as I find it was, that the park and the adjoining houses were situated on black earth soil. That it was so aware is manifest from the evidence of Mitchell himself (he spoke of his firm being geotechnical consultants to the State in the development of the O’Bahn) and, indeed, from the evidence of the experts to the effect that soils in the Modbury area were well known then to contain black earth. The relevance of the State’s knowledge of black earth conditions lies, of course, in the propensity of these soils to be highly reactive to moisture change. Further, the State’s consultant landscape architect for the site, the witness Dexter, conceded an awareness of these matters (p.492).
Put another way, I am satisfied that it was, in and from 1988, reasonably foreseeable by the State that if trees and shrubs were planted in the linear park and they were of inappropriate kinds or were planted in inappropriate numbers or at points too close to Nos 7 and 8, their roots might enter onto those properties and cause soil desiccation and structural damage. The State thus fell under a duty of care to take reasonable steps to ensure that the plantings:
(1)were of appropriate genera and species;
(2)were in appropriate numbers;
(3)were spaced at such intervals from each other and from the southern boundaries of Nos 7 and 8, as to ensure that their roots would not likely encroach upon No. 7 or No. 8 and cause desiccation beneath either property.
Was that duty delegable? On the case as pleaded by the State, the plantings were carried out on its behalf by an independent contractor, namely, Landscape Systems Pty Ltd (through its agent, the witness and landscape architect Dexter), and it relied and was properly entitled to rely on the knowledge and expertise of that party in the design of the plantings, their type, mix, density and planting positions.
No witness representing the State or the Project was called at trial, but it did call Dexter. He said he was the senior landscape architect employed by that contractor in the landscape works on the busway and, in particular, on works adjacent to the subject properties. He had been involved in the preparation of the plan for landscape works P19, and that document, amongst other things, specified the numbers and varieties of species to be placed adjacent to the southern fences of Nos. 7 and 8 and their distances from each other and from those fences. His firm had not, however, supervised the landscaping and planting works and had merely inspected them from time to time. The actual supervision was, he said, undertaken by the Project manager, that is to say, the State.
He commented (at 497/498):
“A.     … We were involved in the design and documentation for the full extent of it. The actual implementation stage in parts of it were implemented by the North East Busway project.
Q. How was the implementation stage divided between North East Busway project and yourself, for example.
A.     On a case-by-case or a section-by-section piece, so they did the contract administration in certain pieces and we did it in other areas.
Q.You happen to know that this particular one is one your company did.
A.No, we did not do the contract administration for the section.
Q.So who did the contract administration for the section.
A.North East Busway project.
Q.     The North East Busway project, as contract administrators, would be responsible for liaising with the contractors who did the actual works.
A.That’s correct.
Q.     And the North East Busway project, as contract administrator, would be responsible for deciding whether the contractors had, in fact, confirmed (sic) with the requirements.
A.That’s correct.” (my emphasis)
He recalled, however, making a site inspection and actually seeing the seedlings being planted adjacent to Kevin Road cul‑de‑sac. He thought that was in about autumn 1988, although other evidence (D9) suggests it was probably a little later than that.
He was well aware of the black earth make-up of the soil at Modbury and then had access to the soil testing results undertaken by the geotechnical engineers on the project – as it happened, the firm to which Mitchell belonged.
I had no reason to doubt anything that he said. It did not, however, support the State’s claim that it properly delegated to Land Systems all relevant duties associated with the plantings – the State may have relied upon the plan P19 and its prescriptions as to plant types, spacings and densities, but it plainly undertook itself the responsibility for the implementation of the plan in that sector of the linear park, in particular for ensuring that only the recommended plants were used and that they were planted in appropriate quantities with appropriate spacings.
Further to that, even had I found that there was proof of a delegation of all relevant tasks, I would have found, on the basis of my prior discussion of authority, that the duty imposed on the State was, in all the circumstances, a non‑delegable one.
Was the State then in breach of the duty of care I have identified?
I am persuaded that it was, and in a number of respects:
(1)It is clear from the evidence of Liliana, of Dexter and from Exhibit P8 that, whilst those planted sections immediately to the south of Nos 7 and 8 may have contained trees and shrubs of the kind specified in P19, they also contained other plantings not therein specified. In particular, I accept the evidence of Liliana as to the clippings taken by her and the identification of them by the expert from the Botanic Gardens (P8). Species of grevillea, acacia, eremophila and eucalypt were planted, but were not specified, and they happen to be varieties described in the evidence as “thirsty”. Such plantings can only have resulted from a failure on the part of the State, through its servants or agents, to properly implement the recommendations of Land Systems in P19.
(2)Further to that, there is the uncontested evidence of Mila that she was present when the Premier, being the responsible government minister, actually planted the large gum tree immediately to the south of their property and which appears in the photographs (see P32). That tree was not part of any planting schedule prepared by Land Systems Pty Ltd, it was plainly a very substantial tree and, on all the evidence, its roots were destined to penetrate beneath No. 8.
(3)The plan P19, in so far as it refers to the planted section south of No. 7, requires plantings at centres of one metre or 1.5 metres, depending upon the variety. I have found, as a matter of fact, that a number of specimens were planted closer to the fence than one metre. I am satisfied that this was the result of poor contract administration by the State and a failure to follow the specifications in P19. On any account, it should not have happened.
(4)With respect to the plantings to the south of No. 8, for reasons that did not emerge, there is no specification as to the centres or spaces between them, yet, plainly, where those same species are elsewhere referred to on the plan, there are such specifications. I am satisfied that the State through its servants or agents was reasonably alerted to the need to adhere to these spacings, yet the evidence discloses, and I have found, that they were not observed in the planted area to the south of No. 8. Some species were in fact placed within one metre of its southern fence. Again, the responsibility for this must fall upon the State.
(5)The planting schedule P19 envisaged the planting of 36 trees and 33 shrubs to the south of No. 8, yet on the evidence of Mila, which I accept, there were 90 stumps left when the first clearance was done. Again, that appears to have been a consequence of poor or inadequate contract administration by the State. The number of shrubs specified to be planted at the rear of No. 7 is 90, which more closely approximates the number counted there, namely, 107. I did not hear any evidence precisely on this point, but it appears to me to be common sense that the number of trees and shrubs planted adjacent to each property bears a direct relationship to their desiccating capacity.
(6)Dexter’s specification for irrigation involved watering for up to six months only, or perhaps a little longer. The State was or should have been aware that once that ceased, there was a substantial risk that the roots of the planted species would likely migrate in search of moisture sources. At some point prior to July 1991, it stopped watering and there is no evidence to suggest it recommended or encouraged the Council to continue it.
(7)Although I note that Dexter did himself inspect the site when seedlings were planted adjacent the Kevin Road cul‑de‑sac, he said, and I accept, that he did not check the plantings to see they were the appropriate species, that they were placed at the appropriate centres, nor, inferentially, that they were planted in the specified quantities: the contract administrator remained responsible for that. Dexter’s omission does not absolve the State.
(8)On all the evidence, I am satisfied and find the State knew or ought to have known that the planting of shrubs or trees, of a kind known to be aggressive moisture seekers, in greater numbers than recommended, using varieties not recommended, and closer to the fence lines of Nos 7 and 8 than specified so that their canopies would likely overhang those properties, created a foreseeable risk of root trespass and damage to the plaintiffs’ properties. Nonetheless, by its servants or agents it proceeded with such planting.
(9)It is not to the point that the root encroachment onto the plaintiffs’ land may not have occurred until after the State ceased to own the linear park. True it is that, on my findings, the damage only arose and the tort was perfected after that time, but the breach of duty occurred at the time of the planting and continued whilst the State remained owner of the linear park and kept the plantings there.

I have already found that the State’s actions ultimately led to the entry of roots under the subject properties, the resulting desiccation and the footing distress.
I am thus satisfied that the plaintiffs have established an entitlement to recover damages for negligence against the State.
LEGAL ISSUES – DAMAGES
A convenient starting point for discussion on damages is Johnson v Perez (1988) 166 CLR 351 at 355 per Mason J:
“The guiding principle in the assessment of damages is compensatory. The object is to award the plaintiff an amount of money that will, as nearly as money can, put him in the same position as if he had not been injured by the defendant: Todorovic v. Waller (1981) 150 CLR 402 per Gibbs C.J. and Wilson J. However, the time as at which damages are assessed can significantly affect the amount actually awarded. This aspect of the assessment of compensation is particularly noticeable in the present era of inflation, with its fluctuating economic values. This is because in times of inflation the amount awarded is likely to be larger if it is assessed at a later rather than an earlier date ... The practice of awarding fixed sums of money worked well when money values and prices were stable. However, in recent times inflation and changing economic values have created complications ... There is a general rule that damages for torts or breach of contract are assessed as at the date of breach or when the cause of action arises. But this rule is not universal; it must give way in particular cases to solutions best adapted to giving an injured plaintiff that amount in damages which will most fairly compensate him for the wrong he has suffered ...”
His Honour went on to discuss the established exception that damages for personal injury would be assessed in the coin of the day, but at p.358 commented:
“In other areas of tort law courts have tended to apply the general rule that damages will be assessed when the cause of action arose. This approach seems less than satisfactory in this era of high inflation. There may be occasions when mitigation is appropriate in the interests of limiting the harm for which the tortfeasor must compensate. On the other hand, the goal of compensation to the injured suggests a later date, particularly in the absence of a voluntary relationship, as in contract. It makes little sense to put the burden of monetary depreciation on the innocent tort victim and to allow the tortfeasor the windfall of paying off his obligation in depreciated currency. As I noted before, legal interest will often be inadequate to offset even a moderate level of inflation. Besides, even if legal interest were adequately indexed, it would not take account of all the changes in the value of the injured goods or interests.”
His Honour went on to note, however, that the later date of assessment was not always the appropriate one and concluded, at p360:
“As the cases to which I have referred reveal, the principles governing the assessment of damages do not permit the application of rigid rules based on categories of actions. Instead, the injured party’s intentions and the surrounding circumstances must be considered in light of the underlying principles in order to do justice between the parties. Where mitigation is possible, an early date for assessment may be appropriate. Where mitigation concerns are not relevant and the circumstances indicate that the injured party would have maintained possession of the goods had the accident not occurred, the date of judgment is the most appropriate date for assessment. Where the circumstances indicate that the property or interest would in some other way have been converted into monetary terms between the time of injury and date of judgment, the date as at which the injury is assessed should reflect the time of the intended conversion.”
In the majority judgment in that case, there was less discussion about those issues, save that it was noted the general rule was that damages would be assessed at the date of the breach, but that “The rule will yield if, in the particular circumstances, some other date is necessary to provide adequate compensation” (p.367).
In the particular circumstances of this matter, I am persuaded that the appropriate time for assessment of the plaintiffs’ losses is the date of the building estimates closest to the date of judgment. I consider it would be unreliable to assess on the basis of aged building quotations, which are well known to fluctuate in ways other than by ordinary inflation or deflation. I will therefore proceed on the basis of the latest repair specifications and estimates provided by Goldfinch and will assess other continuing losses as of today.
Damages Claimed for No. 8
As to No. 8, I have rejected the claim for underpinning, but I am otherwise satisfied that the cost of repairs assessed by Rolfe & Baillie Builders in March 2003 in the sum of $20,108, was properly made out and is recoverable, together with a lump sum in lieu of interest from that time to judgment, which I allow at $1,500.
Further to that, there was the evidence of the valuer Horner (and his report, P2), which was largely uncontested in this respect and which satisfied me that even after repairs are effected, those premises will have suffered a diminution in value of the sum of $21,000.
A third head of damages presented by the owners of that property was based upon the distress and inconvenience occasioned to them by the events during and subsequent to 1995.
I am satisfied on the evidence that those proprietors have, indeed, suffered distress and inconvenience. It was apparent from the evidence of Mila that she is particularly house‑proud and fastidious. It might be that she was more so than the average person, but that is a reality for which the State must account.
Further, I take account of the considerable inconvenience occasioned to the first and second plaintiffs in the purchase and installation of the dripper system and the time and attention devoted by Mila to watering the premises several times a day over nearly three years there and, as well, the boreholes out the front of their premises since 1999. I am persuaded that Mila, in particular, has been fastidious about this, and by any measure it has been a considerable inconvenience.
In making allowance for distress and inconvenience, I can do no more than select a figure which I think fairly takes account of these factors and, in the case of the first and second plaintiffs, I allow an amount of $6,000 under this head.
Summary:               Cost of repairs  $20,108
  In lieu of interest  1,500
  Diminution in value  21,000
  Distress and inconvenience                  6,000
  _______
  $48,608
Damages Claimed for No. 7
I have found myself satisfied that reasonable repair of No. 7 requires the underpinning as proposed by Goldfinch and then cosmetic repair. I am further satisfied that the estimates provided by the builder Complete Building Services (SA) Pty Ltd and the underpinner L J Palmer & Co. Pty Ltd with respect to those matters, are fair and proper amounts as at the later date of 26 August 2003 and, accordingly, I assess the third plaintiff’s loss in this respect in the sum of $133,923, together with a lump sum in lieu of interest to the date of judgment, which I fix at $6,700.
In addition, I am satisfied on the basis of the evidence of Horner and Liliana, that she has suffered a rent loss, not from January 1995 but from November 1995 (when the last tenant vacated) to the date of judgment and that that loss has continued till now and will continue until such time as repairs are completed. In the absence of any direct evidence as to the likely period of time required for completion of underpinning and repair works, I will fix a date three months hence. On that footing, assuming 2004 rental at $9,800 per annum and a 10 per cent reduction as advised by Horner, losses assessed from November 1995 to judgment total $62,070.
I am satisfied the third plaintiff is also entitled to interest on rent not received over that period. As it is a gradually accumulating loss on a progressively increasing sum, it is difficult to calculate a precise interest figure. Doing the best I can and in lieu of interest, I award an amount of $15,000.
The third plaintiff sought to base a claim for damages on a lost opportunity to purchase a property at Maylands in which she was interested, but I was far from satisfied that the asserted loss was sufficiently proximate or, indeed, that she had any firm intention to proceed with the proposed purchase in any event. In that respect, I found her evidence wanting. She did not appear to have seriously pursued the purchase opportunity, anyway, and, further, it would seem that she had other funds available to her to pursue it, had she chosen to do so.
I am further satisfied, on the evidence of Horner and his valuation (P3), that the third plaintiff will suffer a capital loss in the value of No. 7 even after underpinning and repairs are effected. There was no serious or successful challenge to this head of claim and I allow her the amount of $98,000 assessed by Horner.
This plaintiff, too, has sought damages for distress and inconvenience, but I do not regard her loss in this respect as of the same measure as that suffered by the first and second plaintiffs. No. 7 was not her place of residence and her loss has been more in the nature of a commercial loss, for which she is now being compensated. She was not the person involved in the daily irrigation tasks and, indeed, these were carried out by her mother. Nevertheless, the assistance provided by her mother was in the nature of voluntary assistance and to that extent, the third plaintiff may recover. I assess damages under this head in the sum of $3,000.
Summary:               Building costs  $133,923
  In lieu of interest  6,700
  Rental loss  62,070
  In lieu of interest  15,000
  Capital value loss  98,000
  General damages  3,000
  ________
$318,693
Contribution
By its pleadings, the State has asserted that if any damage was suffered by the plaintiffs, it was caused or contributed to, inter alia, by the failure of the Council to adequately maintain, care for and water the shrubs and the failure of the plaintiffs to ensure there were no sewer, mains or stormwater leakages on or beneath their properties.
As to the first of those matters, there was no firm evidence before me to the effect that even had the Council maintained and watered the planting beds in question, that their roots might not still have penetrated the subject properties and caused desiccation. In any event, such contribution, if proved, must be a matter between the Council and the State.
As to the assertion that the plaintiffs contributed to their loss or damage by the failures of sewerage or water systems, I am not persuaded that there was sufficient evidence to point to any real causal connection between any such leakages and the damage suffered. The matter was faintly pursued by Mitchell in his original report, but it was prepared at a time when he was unaware of the artificial watering which was taking place and he did not seriously argue the matter in his later reports or in evidence.
Otherwise, the State contended that the damage suffered by the plaintiffs was inevitably the result of the siting of their particular footing systems on reactive soils. I have already found against that proposition to the extent of finding that tree root desiccation was the effective cause, at least, of the cracking that extended beyond category 0 or category 1 and, in all the circumstances, it is likely that it also caused to some lesser cracking.
Even so, there was plain evidence that both houses did have or were likely to have had some measure of minor cracking at category 0 or category 1 levels, even before the plantings took place. On either account, the respective householders were always prepared to accept and live with that level of cracking. If, in consequence of the State’s negligence, it has been exacerbated to an unacceptable level, then I am persuaded the State must bear the cost of repairing it altogether. On any account, the cracking that was always destined to occur may reassert itself, anyway.
I have already found against the contention that, in not following the recommendation of Mitchell, the plaintiffs failed to properly mitigate their asserted losses. At trial, it was also put to Liliana that at relevant times, she had funds sufficient to proceed with the remedial works on No. 7 that she wished to pursue; that she ought to have expended them at an earlier time and thus mitigated her rental loss claim. There is no doubt, on the evidence, that she had or had access to capital, but I am not persuaded that her damages ought to be reduced because of a failure to so act, and for the reasons that:
(1)her actions, both against the Council and subsequently against the State, had at all times been strongly defended and she had, indeed, failed against the Council because it successfully argued a statutory protection;
(2)there had been no ready consensus as to the appropriate method of rectification and, indeed, the difference of opinion between engineers as to the need for underpinning confronted her with difficult choices. It was reasonable, as I find it, for her to await the outcome of the litigation;
(3)she says, and I accept, that she has been reluctant to expend substantial capital sums in circumstances where the cost of this litigation and the litigation against the Council had been considerable, ongoing and not able to be properly estimated.
In those circumstances, I consider it to have been reasonable of the third plaintiff to await the outcome of these proceedings before committing herself to the very substantial and contentious costs involved in any appropriate measure of rectification.
In conclusion then, I assess the first and second plaintiffs’ damages in the sum of $48,608 and the third plaintiff’s damages in the sum of $318,693.
I will hear the parties as to any other matters.