24. There was no general agreement between the witnesses as to the alignment of the property (that is, which direction was North). For the purpose of these reasons I have accepted that the frontage of the property to the street is its western boundary. On that basis, the site slopes from the north west to the south east. The driveway is slightly to the south of the middle of the frontage and descends eastwards towards the front door before turning north to enter the garage. Water travelling down the driveway is intercepted by a grated strip drain. The large paved area where the driveway turns in front of the house is drained by a square grated drain with the paving generally graded towards it. Between this paved area and the house there is a narrow garden. Quite obviously, none of the water that enters this garden area from above could be taken away by the driveway drainage, nor would that drainage take away any water passing underneath the driveway paving. Since the level of the block seems to be lower in this position the agricultural drain to be installed below the garden was particularly important.
25. On the northern side of the house the site has been substantially excavated with batters sloping from the original ground level in the north descending southwards towards the house but with no appreciable flat area between the foot of the batters and the side of the house. Any water flowing down the batter of the excavation would reach the house unless intercepted by an appropriate storm water system. The same consideration applies to the western side of the manager's flat which is the north western corner of the building.
26. Substantial ingress of water has been experienced from both the western side of the house near the front door and into or under the northern wall. The house is stepped down the hill so that the front of the house is at ground level but with a lower level constructed below that at the rear. During the inspection I noted a substantial quantity of water ponding behind an internal sub-floor wall uphill from the lower section of the house. Immediately to the east of the place where this water was ponding there is a sub floor area called on the plans a "plenum", where the cooling system has been installed. The batter of this area has been paved in shotcrete to provide a sloping concrete floor, the lower end of which extends down to the western wall of the bottom section of the house. Since there are habitable rooms immediately to the east of this wall and in order to avoid water penetration at this point the plans provided for a spoon drain to be constructed, the finished surface of which was to be below the floor level of the floor slab of the lower area. In fact, the spoon drain was constructed above the level of the slab and, although there is an agricultural drain below the concrete floor in this position, a video tape passed through the drain shows it to be partially blocked. This is a replacement drain. During construction the original outlet to this drain was found to be wholly blocked and the present secondary outlet was then constructed.
27. There has been substantial water ingress into the lower area of the house through this western wall, which was not tanked. This has manifested itself in salts leaching into the stone tiles on the inside of the wall, the timber flooring in the passageway expanding, buckling and breaking, floorboards in rooms cupping and a general feeling of dampness.
28. In the upper part of the house there is a similar leaching of salts into the stone tiles in the living area near the door and western window. This is not as noticeable as it is in the lower area but it has caused them to change colour. Tests on the concrete slab have shown it to have excessive water content.
29. Mr Browning attributed the water penetration to the failure of the Builder to grade the surface of the soil away from the building at the foot of the cut on the northern side of the house so as to stop water from flowing up to the house. He also criticised the installation of an agricultural drain by the Builder extending from a drainage pit to the west along the wall of the manager's flat. He pointed out that this enters the pit at the same level as the inlet and outlet pipes for the stormwater so that, at times of high water flow it would be expected that water would flow out of the pit along the agricultural drain depositing water along the northern side of the house and thereby contributing to the sub-floor water penetration. The significance of the problem derived from the fact that the pit was carrying the whole of the uphill stormwater outflow from the roof of the building.
30. The second problem highlighted by Mr Browning was the failure of the sub-floor drainage system which was intended to be affected by the construction of the spoon drain. Because the level of the spoon drain is higher than the finished wall and the western wall separating the sub floor from the lower section of the house was not tanked, any water that entered the sub floor would pass through the wall and dampen the lower area of the house. He also criticised the construction of the agricultural drain beneath the spoon drain which was, he said, made of different materials, had insufficient fall and, in some areas, negative falls.
31. It was suggested to Mr Browning in cross examination that the problems with the agricultural drainage system were caused or contributed to by the landscape contractor covering some of the pits. The drainage plan required the tops of the pits to be covered by grates but when the Builder left the site it covered them with concrete lids in order to prevent dirt or rubbish entering the stormwater system during landscaping. The suggestion on behalf of the Builder was that these ought to have been removed and replaced by grates after the landscaping was done. However it was for the Builder to construct the pits in the manner required by the drawings. The expressed concern to prevent the stormwater drains from being blocked by soil during landscaping could have been addressed by placing something underneath the grates rather than leaving the system in a condition where, to all appearances, the concrete lids were intended to remain. In any event any failure by the Owners to do this was not shown to be a contributing factor to the ingress of water to the house. Further, from the levels, it does not seem to me that these pits would have been effective to take any surface runoff anyway. What the plans required was for the soil to be graded away from the house, not graded towards these pits. They were certainly not positioned in a way to catch surface runoff before it reached the house even if they had been covered with grates instead of concrete lids.
32. Another aspect of the stormwater drainage lies in the drain intended to be located under the garden and the front door. As stated, because of the lie of the land this was an important potential source of sub floor water ingress and the drainage plan required a stormwater drain to be laid along the eastern side of the house to collect groundwater and direct it to the south in accordance with the design. According to Mr Browning's evidence, excavations on the south western corner of the house failed to find any pipe in this area, indicating that no such pipe had been laid. There is no evidence that there was any pipe laid in this area so I find on the balance of probabilities that the Builder failed to lay one. This is highly significant because, to the extent that rain water from above the garden or water travelling down from the street under the concrete paving has contributed to the subfloor water penetration problem, it would seem that this has been caused, wholly or in part, by the failure of the Builder to install an agricultural drain in this area as required by the plans to take that water away.
33. There is no evidence before me to establish any fault on the part of any of the other contractors in regard to the agricultural drainage. Evidence was given on behalf of the Owners by Mr John Briggs who undertook the landscaping works around the house. Attached to his witness statement are a number of photographs indicating the condition of the site before the landscaping was commenced. These photographs would not suggest that the landscaping subsequently done had any significant effect on the flow of water towards the house. They show the soil to be graded by the Builder towards the house rather than away from it as the plans required. They also indicate that there was some backfilling of soil against the northern wall of the house by the Builder before the landscaper started work. This looks in the photograph to be uncompacted fill.
34. The only contrary evidence was by Mr Dobson, the site foreman on the project employed by the Builder, who said that he believed the agricultural drainage was done in accordance with the civil engineering plans. However a comparison between the photographs tendered and the plans show that the bottom of the cut along the northern side is too close to the house and the ground has not been graded away from the house as the plans required. In addition, there is the evidence of Mr Browning to the effect that the agricultural drain at the front of the house is missing. I do not think that the general statement of Mr Dobson can stand against this other specific evidence.
35. There is no evidence as to any cause for the entry of water of water to the subfloor area other than the failure of the agricultural drainage system that was intended to carry it away. A video taken of the interior of the various pipes show instances of broken pipes, pipes with negative fall, and, in the case of the pipe under the spoon drain under the house, pipes that are partially obstructed. It was conceded on behalf of the Owners that the landscaping contractor removed a pit below the south eastern corner of the house but that is downhill of where the water was entering the subfloor and cannot have contributed to the problem. In the absence of any other explanation for the presence of water in the subfloor area it must be attributed to the failure of the Builder to grade the ground away from the house and construct the agricultural drainage system in the manner required by the design.