52 Inferences 'from actual facts that are proved are just as much part of the evidence as those facts themselves' (Jones v Dunkel (309) (Menzies J)).
53 I am also mindful that a circumstantial case which is reliant on deduction by a process of elimination is potentially fraught with the fallacy that a hypothesis is correct merely because it is the only one left. Findings must be supported by evidence and an assumption or conjecture is not evidence (Swick Nominees Pty Ltd t/as Swick Drilling Australia v Norncott Pty Ltd [No 3] [2013] WASC 173).
54 The assessment of the credibility or reliability of evidence is a multi-factorial task. The appearance and demeanour of witnesses are relevant factors, but there is a danger in too readily drawing conclusions about truthfulness and reliability solely or mainly from such considerations. Judges are encouraged to 'limit their reliance on the appearance of witnesses and reason to their conclusion, as far as possible, on the basis of contemporary materials, objectively established facts and the apparent logic of events' (Fox v Percy [2003] HCA 22; (2003) 214 CLR 118, [30] - [31] (Gleeson CJ, Gummow, Kirby JJ)).
55 It is also useful to take into account the cooperativeness and frankness of witnesses and their willingness to make concessions.
56 An expert is permitted to give evidence of an opinion (which would otherwise be hearsay) with respect to a technical, specialist or esoteric factual issue which requires expert elucidation if he or she is qualified by training or experience to do so. Opinion evidence is admissible for the purpose of assisting the court to make findings of fact.
57 Opinion evidence, and findings derived from the same, must be based upon facts or stated assumptions that are proven (or bear sufficient correlation to facts which are proven) and must be explained in such a way that the court can comprehend it and make the necessary findings, or at least understand why it should be adopted or deferred to. (Pownall v Conlan Management Pty Ltd (1995) 12 WAR 370; Pollock v Wellington (1996) 15 WAR 1, 3 (Anderson J); Beer v Duracraft Pty Ltd [2004] WASCA 192 [78] – [80] (McLure J); and Makita (Aust) Pty Ltd v Sprowles [2001] NSWCA 305; (2001) 52 NSWLR 705, [64] (Heydon JA)).
58 As with lay witnesses, the court is entitled to accept all of a particular expert's evidence, or none of it, or accept some and reject the rest, or simply put it to one side (Ramsay v Watson (1961) 108 CLR 642; 645). In this way findings can be drawn from evidence and opinions of more than one expert, irrespective of who adduced the evidence.
59 The importance of expert evidence and its weight may also depend to some extent on the degree of specialisation involved in the relevant expert field, because some fields are more esoteric than others.
60 But, I stress that the purpose of expert evidence is not to educate the court so that it may then form and rely exclusively upon its own analysis. The court cannot substitute a scientific or investigative role for its fact-finding role.
61 As will be seen, the issues in this case involve a number of technical matters. Some of these are particularly esoteric (such as the chemical properties of materials such as concrete and Aquron, and their reactivity inter se) whilst others are more accessible to a layman (such as the basic principles of hydrology).
An overview of the evidence
62 Four lever arch folders of documents were received in evidence by consent as exhibits 1 – 4 (the Trial Book). The Trial Book (TB) included plans, specifications, contractual documents, technical reports, photographs and other material. Other documents were received in evidence separately.
63 Pindan adduced oral evidence from two lay witnesses, Mr Brett Kinner and Mr Stephen Flint, and two experts, Dr Zurhaar and Mr Allan Lundorf of Golder Associates.
64 Mr Kinner was Pindan's construction manager with overall responsibility for performance of the Head Contract. He testified as to Pindan's management structure for the contract and the roles of himself and the persons who worked below him, including a contracts administrator, a junior contracts administrator, the senior site supervisor and two other site supervisors (one of whom was Mr Flint).
65 Those people all worked full-time on the Site.
66 Mr Kinner and Mr Flint were patient and respectful witnesses and appeared to confine their responses to things which fell within their expertise or experience on this particular project, and they made concessions.
67 They gave evidence as to the construction of the slabs including the laying of waterproof membranes. They were cross-examined about the possibility that defects (such as gaps and tears) were left unremedied before the concrete was poured. Without being too adamant about it, they regarded this as a reasonably remote possibility.
68 Mr Flint readily conceded that photographs of the slab preparations for the administration building (ie, before any concrete was poured) showed some tears in the waterproof membrane. He accepted (ts 404) that that sort of damage could be caused by a star picket that had held a formwork shutter in place. He stated that he 'would very much hope that got repaired before we poured'.
69 On my assessment of the evidence of Mr Kinner and Mr Flint, it is unlikely that Pindan knowingly allowed any departures to occur from the contractual requirements or proper building practice (but the possibility that some departures in fact occurred cannot be ruled out: see [103]).
70 Overall, I have a high level of confidence in their evidence about the construction of the slab.
71 My confidence is supported and enhanced by their uncontested evidence that JCY and KBR sent representatives to the Site to inspect the work in progress, and the preparations for each and every slab were inspected by an engineer before any concrete was poured. In other words, Pindan's work was checked.
72 There was evidence from Dr Zurhaar and Mr Trinder which suggested that best practice was not necessarily mandated in the drawings in relation to the coverage of the waterproof membrane. But my concern is to make findings about the as-built situation, as to which the drawings are reliable evidence.
73 For the defendant, Mr Vincent gave evidence, as well as his daughter-in-law Ms Leanne Vincent, and Mr Barry Coveney. Mr Peter Trinder of BG & E Materials Technology Pty Ltd gave expert evidence.
Further findings of fact about the works
74 I turn to make further findings relating to the construction of the buildings, problems with leaks and drainage and the timing, location and extent of the failures in the vinyl flooring. Much of this is not in dispute, but I will make findings on some contentious matters as required.
The Site and buildings
75 The Site originally consisted of a sloping, undeveloped area of approximately 4 hectares which was part of a low-lying wetland.
76 The Site was first stripped of vegetation and topsoil. It was then cut, filled with clean fill and levelled to a uniform elevation of 26.80 m AHD.
77 Groundwater was encountered in some deep excavations (more than 3 m) and pumped away. This occurred in the deepest parts of a sewer line running the length of the Site from north to south between the locations of the administration and visual arts buildings (to the east) and the performing arts, library-café and basketball courts (to the west). Groundwater was also encountered at the base of a lift pit in the specialised learning building (Mr Kinner: ts 91 – 92) and the hydrotherapy pool in the Kim Beazley building (Mr Flint: ts 386).
78 Approximately 200 concrete soakwells (1.8 m diameter; 1.2 m depth) were installed throughout the Site to drain rainwater from roofs and paved areas.
79 Concrete strip footings were then laid to support the edge of each slab (external footings). Typically external footings are 300 mm deep, but they vary up to 450 mm in some buildings and 500 mm in the basketball building (TB 1028).
80 Isolated concrete footings were interspersed to support specific structural features, such as columns. These footings were larger and deeper than the strip footings.
81 A continuous 200 micron thick waterproof membrane (overlapping plastic sheeting) was laid directly onto the soil (at 26.80 AHD) that was within the external footings.
82 In accordance with the drawings the external footings (and the isolated footings) were not laid on, or wrapped in, a waterproof membrane. The outsides of the external footings were parged (painted) with a waterproof membrane before being back-filled with soil.
83 As such, the inner-sides and bases of the external footings (and the isolated footings) now lie in direct contact with the ground soil.
84 Steel reinforcement mesh for each slab was positioned a few millimetres above the waterproof membrane. Steel cage reinforcement was used for the isolated footings.
85 The waterproof membrane was penetrated where necessary by isolated footings and plastic and copper plumbing which lies under the slab. Photographs (TB 606, 614 - 616, 617, 619, 625) appear to show that the plumbing penetrations were carefully taped to the membrane to achieve a waterproof junction.
86 Plastic conduits for in-floor services were laid between the waterproof membrane and the reinforcing mesh (see TB 625).
87 The slabs were laid 100 mm thick (ie, the finished floor level of every building is 26.90 m AHD: 26.80 plus 100 mm for the slab) except where they overlapped the external strip footings, in which case the slab-edge was thickened by an additional 200 mm.
88 In other words, the total thickness of the slab and the footing where they overlap is now between 600 mm and 750 mm (800 mm in the case of the basketball building). Bearing in mind that the top of each slab is 100 mm above ground level, the depth of footing/slab below ground level (bgl) varies from 500 – 650 mm (700 mm in the basketball building).
89 Mr Trinder contended that the drawings stipulated that the thickened edge of each slab was to be 100 mm thicker (400 mm in total), so that the slab/footing depths would vary from 600 – 750 mm bgl (800 mm bgl in the basketball building).
90 The drawings are ambiguous on this and could be interpreted as requiring the thickness of the slabs above the external footings to be either 300 mm (TB 1026) or 400 mm (TB 1028). My findings as to causation (ie, as to Pindan's hypothesis, the groundwater hypothesis or the leak hypothesis) must be based on the as-constructed situation. For unknown reasons, no-one seems to have investigated the matter on Site, so I am left to make findings based on the drawings. On the balance of probabilities I prefer the view that the drawings stipulated that the slab above each external footing was to 300 mm thick and not 400 mm. In my opinion the references to 300 mm were intended to relate to a typical slab and the sole reference to 400 mm was only given as an example of an atypical slab or, more correctly, how an atypical slab detail would be noted on a drawing. I am satisfied that the typical slab thickness above external footings is 300 mm but at the appropriate juncture I shall consider both possibilities (see [201]).
91 Each slab was left to cure (dry and harden) for several weeks after being poured.
92 The superstructures comprising steel columns, beams, rafters and purlins were built next.
93 Walls were built using hollow clad-framed panels or pre-cast concrete panels with a typical thickness of 90 or 100 mm.
94 Each building was roofed with metal sheeting.
95 Steel framed windows and doors were installed.
96 Concrete verandahs were poured at 26.90 AHD (the level same as the internal floors).
97 Suspended ceilings were installed with recessed lighting and ventilation openings.
98 Moulded (MDF) skirtings were installed at the junction of the walls and slabs.
99 Hydraulic, electrical, mechanical, painting, carpentry and similar services were installed as appropriate throughout the above-mentioned process.
100 Seattle then laid the floor treatments.
Possible damage to the waterproof membranes
101 The setting out work for each concrete pour, as well as other setting out work, had the potential to tear or puncture the waterproof membrane. For instance, based on some photographs I find that Pindan occasionally drove steel rods into the membrane to secure string-lines (TB 596, 605, 609 – 610, 612, 624 - 625). Pindan sometimes used star pickets to hold formwork in place and for other purposes (TB 594 – 595, 557, 608, 613 - 614, 616, 615 – 623, 625 - 627). I am satisfied that some of these pickets punctured the membrane. The punctures needed to be patched before the concrete was poured.
102 But there is evidence that they were not patched. Mr Trinder pointed to a photograph (TB 595) which showed concrete residue on the lower sections of some star pickets which, in turn, suggests that they had once been embedded in wet concrete to that depth. That, in turn, suggests at (ts 791 - 792, 796) that star pickets were not removed until after the concrete was poured around them, which was too late to repair any punctures.
103 That is a persuasive hypothesis. The relevant photographs appear to show that everything was in readiness for the concrete pour and it is unlikely that the supporting pickets were removed until the formwork was no longer required. I have kept Mr Trinder's hypothesis in mind, but I comment that there is no evidence that the practice of using star pickets in this way was widespread on the Site. So far as the photographic evidence as a whole is concerned, penetrations could only have occurred occasionally and on the perimeter of the slab and thus affected a very small proportion of the whole. (I would estimate a small fraction of 1%).
104 I repeat my observations at [67] – [69] above and accept that the laying of the slabs was taken very seriously. The possibility is remote that damaged or incomplete membranes went unnoticed and/or unrepaired as a matter of routine. It is most improbable that Pindan's staff and contractors, or the superintendent's and engineer's representatives, failed to attend to this appropriately as a general rule.
105 In short, whilst the possibility of an occasional lapse could never be ruled out, based on the evidence of Messrs Kinner and Flint the possibility that such occurred on a regular or widespread basis is difficult to accept and I reject it.
Concrete slab moisture levels
106 The dates of the concrete pours, installation of roof-cover (rain-protection), moisture testing (and results) and vinyl installation for each building are set out below.
Building | Concrete Pour | Roof Cover | Vinyl Install | Concrete Moisture |
| | | | | 6.9-7.1% (04/10/07, 15/10/07) |
| | | | | 7.2-7.3% (12/11/07) 7.0-7.2% (12/07, 01/08) |
| | | | | 7.1-7.2% (12/11/07) 6.9-7.2% (Jan 08) |
| | | | | 7.1-7.3% (12/11/07) 6.9% (27/03/08) |
| | | | | 7.1-7.4% (29/07/08) 7.2% (12/08/08) 7.1-7.2% (15/10/08) |
| | | | | |
Specialist Learning (ground floor) | | | | 7.1% (12/08/08) 7.1% (06/10/08) 7.1-7.2% (09/10/08) 7.2-7.3% (15/10/08) |
| | | | | 7.1% (09/10/08) 7.5% (16/10/08) |
107 It is to be noted that the retained moisture density remained relatively constant between the pouring of each slab and the installation of the vinyl, even after roof cover was provided. According to the lay and expert evidence, this was unexpected and unusual in that the density of retained moisture should fall as a slab cures, especially in dry weather or after roof cover has been provided.
The application of the Aquron
108 Mr Vincent gave uncontested evidence about the application of the Aquron and I make the following findings:
(i) Each slab was swept and tested with water to identify any high spots. These were then ground down by a contractor engaged by Pindan. (ii) The surface was sanded and watered to provide preliminary hydration of the concrete.
(iii) The slab was measured into 100 m2 sections.
(iv) Once the water had dissipated 20 litres of undiluted Aquron was sprayed in two passes at right angles to each other so as to ensure an even spread (ie, 20 litres per 100 m2).
(v) No problems were encountered with either the hydration of the concrete or the absorption of the Aquron.
(vi) Occasionally a small quantity of Aquron pooled in a low spot. This was left for 20 – 30 minutes to be absorbed into the slab. Any remaining Aquron was swept around with a broom until it dissipated or was absorbed into the slab.
Water damage caused by leaks 109 It is apparent from the evidence (most notably Mr Trinder's second report) that best practice was not employed in connection with waterproofing the outer walls of many of the buildings. It is also apparent that there were a number of problems with leaking roofs.
110 Based on the evidence as a whole, particularly that of Mr Kinner, I find that flooring was affected by water from external leaks in 2008 and 2009 as follows:
(i) The administration building: The conference room, offices and the disabled toilet. Only the last had vinyl flooring. (ii) The performing arts building: The property and chair store (carpet).
(iii) The Kim Beazley building: Vinyl flooring blistered around the perimeter walls in classrooms 1 and 2 (near water-damaged skirtings), in the activity area in several places, in the western foyer entrance and adjacent to doors in the north wall of classrooms 3 and 4. These leaks were caused by poor external drainage and gaps in doors and flashings. There were also leaks through the roof and light diffusers in classrooms 1 and 4.
(iv) The middle school (north): In the D & T room (vinyl), staff room (carpet) and a female toilets (tiles). These leaks came from the roof.
(v) The middle school (south): The staff, planning and collegiate areas, classrooms 3, 6 and 8, all caused by roof leaks. None of these areas had vinyl flooring.
(vi) The library-café: The resource area, inside the main entrance, inside the media viewing room and in the food preparation area of the café (Ms Vincent testified about this). All of these leaks came from the roof. The café had vinyl flooring.
(vii) The basketball courts: Vinyl in the northern entrance. These leaks came through door flashings when rain fell from a particular direction.
(viii) The specialist learning building: Vinyl in food studio 1 and carpet in the staff study. These leaks came from the roof.
111 All of the damaged vinyl was repaired or replaced at the time. None of the abovementioned areas is proximate to an area where the vinyl was found to be blistering in 2011, except for the toilet in the administration building which was adjacent to a server room, all of the areas in the Kim Beazley building, and food studio 1 in the specialised learning building.Areas where vinyl was found to be blistering in 2012
112 By reference to the evidence of Mr Kinner read with exhibit 8, and the structural drawings, I make the following findings as to the areas where vinyl flooring was found to be blistering in 2011. The combined slab and external footing depths (slab-footing depths) are included:
(i) The administration building: An area adjacent to a toilet and a storeroom. I estimate that this represents slightly less than 50% of the vinyl flooring in this building. The slab-footing depth is 600 mm. (ii) The performing arts building: All of the vinyl in the foyer and passages, representing approximately 90% of the vinyl in the building. The slab-footing depths are 650 mm, save for two which are 600 mm.
(iii) The Kim Beazley building: All of the vinyl in classrooms 1, 2, 3, 4 and 5, the lifeskills and activity areas and all passageways. This represents about 75% of the vinyl flooring in the building. There is a photograph at TB 888. The slab-footing depths are a combination of 600 and 650 mm, with one 700 mm.