Determinations issued
To read all the determinations in summary or in full, go to: www.dbh.govt.nz/determinations
Determination 2007/37
Dispute about the code compliance of a liquid-applied membrane
The owners of a balcony deck applied for a determination after the territorial authority refused to issue a code compliance certificate for the house on the basis of not being satisfied that a liquid-applied membrane on the balcony complied with clauses B2 and E2 of the Building Code.
The building work related to the membrane applied to the deck of a large timber-framed external balcony situated at the upper level of a two-storey house. The balcony spanned most of the north elevation, constructed over living spaces. The balcony deck was finished with a fibreglass-reinforced vinyl membrane, with upstands under the main wall and balustrade cladding, and water discharged into a metal gutter at the front of the balcony.
According to the manufacturer, the membrane was applied to a plywood substrate in accordance with its standard specification, which was applicable at the time of installation.
The Department commissioned an independent expert to inspect and report on the building work. The expert's report was considered by the Department, along with the parties' submissions.
The submissions
The applicants noted that the territorial authority had refused to issue a code compliance certificate as it did not accept that the membrane was an alternative solution. The consent for the building work was issued before the Building Act 2004 came into force.
The applicants also set out the verification, service history, direct comparisons, testing and product approval of the membrane.
The territorial authority did not make a formal submission. However, it did express concern that a favourable decision could be interpreted as universal acceptance of the membrane.
The determination
A draft determination was sent to both parties. The applicants accepted the draft. The territorial authority accepted the outcome of the determination but was concerned that the only action required to make the system code-compliant was recoating.
The territorial authority also noted that, while the product might comply with the Code in this case, the supplier and the industry could interpret the decision as being a product endorsement. The territorial authority was not making any judgment about its quality, but did not believe the supplier had adequately supported the alternative solution application.
The Department took into account the territorial authority's concerns about the lack of independent product testing or verification of the membrane and the product endorsement issue.
As the use of the membrane was considered to be an alternative solution, the Department applied two criteria used to assess a building product in a particular application for code compliance. These criteria are proven in-service performance and quality of the finished application.
As to the first criterion (in-service performance), the membrane system was provided by an established manufacturer and had been in use for 23 years. After 3 years of service, there was no evidence of moisture entering the building. The expert noted that he had observed this particular membrane over the past 20 years, and any failures could be attributed directly to associated poor construction detailing and workmanship and not to product failure.
With regard to the second criterion (quality of the finished application), the most common problem with liquid-applied membranes is inadequate quality control at the time of application. In this case, the membrane had been installed to a level of trade practice regarded by the expert as being 'of a high standard', and in accordance with the manufacturer's recommendations and industry guidance documents.
The Department felt that, when considered together, these two criteria provided sufficient grounds to conclude that the membrane system, in this particular case, complied with Clause E2.
However, it was accepted that remedial work was necessary to remedy pin holes in the surface of the membrane, which prevented it from complying with Clause B2. Because this fault was minor, it was concluded that satisfactory rectification would result in it remaining weathertight and thus complying with Clause B2.
The Department agreed with the territorial authority's general points on the need for applicants to provide adequate documentation when seeking a building consent for an alternative solution.The Department also emphasised that the determination should not be taken as a form of product endorsement, appraisal or certification. If a particular membrane system has been established as being Code compliant on one building, this does not mean the same system will be Code compliant in other situations.
The decision
It was determined that:
- the membrane did not comply with Clause B2 of the Building Code, so the territorial authority's decision to refuse a code compliance certificate was justified
- once the pin hole defects were rectified, the membrane would comply with the provisions of the Building Code.
Determination 2007/23
Dispute over a refused code compliance certificate for a garage
The owner of the garage applied for a determination after the territorial authority refused to issue a code compliance certificate, on the grounds of being unsatisfied that building work on the garage complied with the Building Code.
The building work
A detached single garage was converted into a double garage attached to an existing house. One wall of the double garage was an existing concrete block boundary wall, the other external walls were timber frame clad with timber weatherboards. The garage was unlined, except for a length of internal wall between the garage and the house. The existing concrete slab floor of the garage was extended. The floor of the garage was 50 mm above the level of the drive.
The determination related to the clearance between the concrete drive and the bottom of the timber cladding at each side of the garage door. The clearance varied from approximately 20 to 80 mm.
The submissions
The applicant described the location and construction of the garage. The applicant also noted the garage floor did not have the 100 mm clearance set out in E2/AS1 but had a 50 mm clearance above the driveway. Water could not enter the garage front entrance due to the driveway being either level or sloping away towards the kerb.
The territorial authority did not make a submission.
The determination
Both parties were sent a draft determination, which they accepted without comment.
Because of general interest in the application of E2/AS1 to unlined garages, the Department further amended the draft, expanding the discussion on E2/AS1, but with-out altering the substantive decision.
The final determination included relevant extracts from the Building Code and Acceptable Solution E2/AS1.
The limits on application of Clause E2.2 mean that if moisture from outside is no more harmful than moisture from inside, then Clause E2.2 does not apply. Therefore, the first question to answer in this case was if moisture from outdoors would cause more damage than moisture from indoor sources.
Clause E2.2 does not apply to buildings such as open barns, so there is no need for the cladding of such buildings to be weathertight. However, while not required to comply with Clause E2, the cladding is still required to comply with other clauses, in particular B1 and B2.In the absence of specific information about the harm likely to arise from internal moisture in this case, the Department decided that the garage was required to comply with Clause E2. Even so, the Acceptable Solution E2/AS1 did not necessarily apply. In fact, Paragraph 1.2.1 of E2/AS1 excludes 'garages and other unlined structures'.
The Department took the view that E2/AS1 did not apply, as it excludes unlined garages. This did not mean that Clause E2 itself does not apply, but the requirements of E2/AS1 could have been 'in excess of the minimum required by the Building Code' for this garage.
In an unlined garage, any moisture that reaches the framing from outside is not likely to cause undue dampness or damage to building elements contrary to Clause E2.3.2, because:
- a higher level of dampness is acceptable in a garage than in a habitable room
- framing timbers (with the possible exception of bottom plates) are less likely to be damaged by moisture because they are exposed to the atmosphere and the moisture is likely to dissipate before it can result in any damage.
However, though a lesser degree of weathertightness is acceptable for unlined garages, framing members and claddings must still comply with Clauses B1 Structure and B2 Durability.
In this case, even though some of the provisions of E2/AS1 might be in excess of minimum requirements, it may still be used as a benchmark or guideline. The only requirement of E2/AS1 that needs to be considered is the clearance between the bottom of the cladding and the adjacent ground or paved surface. The purpose of that clearance is to:
- protect the bottom plate against water splashing up behind the cladding, and
- protect the bottom plate and the cladding against moisture in direct contact with the bottom of the cladding, including free water and moisture in any debris that might accumulate.
The bottom plates of the garage were H3.1 treated and protected against the accumulation of external moisture by a damp-proof course. It was expected the weatherboards would also be H3.1 treated.
The applicant submitted that the specified clearance to the bottom of the cladding was not needed, because the slope of the driveway meant water could not reach the front of the garage. This submission was not accepted, because (regardless of the driveway slope) it was still possible for rain-splash and water to run off the face of the building, meaning that debris (and water) could still accumulate beneath the cladding.
It was also noted that the clearance between the cladding and the adjacent ground or paved surface was relevant to Clause B2, not only to protect against moisture, but also to facilitate normal maintenance.
Compliance with the Building Code
The Department was of the view that the garage opening complied with the two requirements of Paragraph 9.1.3.4 of E2/AS1. However, the base of the weather-board cladding at each side of the opening did not comply with the clearance required for lined garages. While it was recognised that some clearance (less than the 100 mm required by E2/AS1) could provide adequate protection, current clearances were not accepted as being sufficient.
It was concluded that the clearance between the driveway and the bottom of the weatherboard cladding on the front of the garage did not comply with the Building Code.
The applicant proposed that a drainage channel be installed across the front elevation of the garage. In the absence of proper plans and specifications for such a channel, the Department observed (but did not determine), that such action could make the garage Code compliant.
The decision
It was determined that the building work did not comply with Clause E2 of the Building Code. The territorial authority's decision to deny a code compliance certificate was confirmed.