Seventy-seven Determinations were issued last year, 60 of them on weathertightness matters. The following are summaries of two of the weathertightness Determinations issued in November.
In both cases the owner disputed the territorial authority's (TA) decision not to issue a code compliance certificate (CCC) and applied for a Determination. Building Controls (the Building Industry Authority at the time) was asked to determine whether the monolithic cladding on each house complied with the external moisture requirements (E2) and durability requirements (B2) of the Building Code.
To read Determinations in full, see the register.
House 54, issued 15 November 2004
The house is built on two levels, in a high wind zone and is a moderately complex shape. It has two open tiled decks on the upper level, one of which is constructed over the kitchen, while the other is supported on an extended upper level joist and post system at its outer edges. The house has no eaves and the various gable ends are flush finished.
The Authority received submissions from the TA and the owner, and it commissioned a cladding report from an independent expert. The expert took 29 moisture readings, 23 of which were above 18 percent, with some readings as high as 40 percent.
The most significant areas of moisture ingress were:
- the bottom plates, where moisture was entering through the base of the cladding, because of the lack of a capillary gap between the cladding and the concrete foundation
- the tops of the beams and columns supporting the deck over the kitchen, where moisture was entering because of inadequate sealing to the flat tops of the beams and columns
- the base of the columns on the deck, where moisture was entering through the inadequate seal between the tiled deck and the fibre-cement column
- boundary joists to the rear deck, where the moisture levels may be due to the penetration of the deck membrane by the fixings for the corner block support to the screen.
The expert also noted other deficiencies in the cladding.
- The waterproofing membrane under the tiles turned up under the fibre-cement walls had tile grout in the gap, so there was no capillary break between the back of the fibre-cement and the membrane along the walls and the columns.
- Penetrations were fixed directly into the cladding and not sealed effectively.
- A polystyrene fascia covering to a horizontal joint in the cladding was trapping water and preventing ongoing maintenance inspections to ensure the horizontal joint remained weathertight. Furthermore, the butt joint found behind the fascia is not a horizontal control joint and will not operate like one.
- Ground levels in some areas are too close to the bottom edge of the cladding.
House 58, issued 29 November 2004
The house is single-storey, in a low wind zone and the external walls have monolithic cladding. The house is of a fairly simple shape, but the roofs have several complex valley and wall/roof junctions. The flat roof eave projections are 300 mm wide. An attached 125 mm gutter gives further protection to all the eaves. The main roof verges have no projections.
The Authority received submissions from the TA and the owner, and it commissioned a cladding report from an independent expert.
The expert took 23 moisture readings that were above 18 percent, with most readings in the high 20 percent range and some as high as 40 percent. These excessive moisture readings largely occurred under windows or at the bottom plates of the walls. The expert considered that it was possible that the ingress of moisture could have weakened the untreated timber behind the cladding.
The expert also found that numerous cracks were evident in the cladding on all elevations of the building.
In addition, the expert also noted other deficiencies in the cladding.
- The exterior joinery units have standard aluminium head flashings, but the cladding finished hard against the flashing. There is no evidence of inseal strips or sealant under the jamb flanges of these units.
- There are no flashings to the head and jambs of the garage door openings.
- No vertical control joints have been installed.
- The cladding overlap at the foundation wall is insufficient at some locations.
- There is insufficient ground clearance to the cladding adjoining the garden areas, and the cladding is buried in the paving outside the front and garage doors.
- At four cladding/roof junctions the flashings are face mounted and driven rain can enter behind the cladding at these areas.
- The junctions between the vertical edge of the cladding and the butyl rubber flat roof membrane have the potential to permit moisture ingress.
Some penetrations are not properly sealed.
In both cases, the Authority found the cladding was not installed according to good trade practice or to the manufacturer's instructions. As a result, there were a number of defects which had caused penetration of moisture through the cladding. The Authority determined the cladding systems as installed did not comply with Clause E2.3.2 of the Building Code.
Because the faults identified were widespread and serious the Authority could not conclude that once the faults identified in the expert's report were fixed the claddings would be Code compliant. A final decision on the best remediation options can only be taken after more extensive investigation and careful design of the changes by an appropriate expert. In both cases, the Authority confirmed the TA's decision not to grant the CCCs.