The New Zealand building code is performance-based, and to facilitate proof of compliance the Building Industry Authority publishes Approved Documents that provide tests or calculation methods (Verification Methods) and “cookbook” solutions (Acceptable Solutions).
Currently the Acceptable Solution for the prevention of penetration of moisture into a building that will cause undue dampness or damage to the building deals only with generic materials such as timber weather boards, brick veneer and stucco on light timber framing.
The Verification Method contains test methods to be carried out in a laboratory. Not only can such tests be costly, but they may also not take account of site conditions or of the protection provided by the layout and orientation of a building.
This paper will examine the possibility of an additional Verification Method that will show compliance with the performance based building code by dealing with the adequacy of the building envelope in terms of such issues as its materials and systems, the joints within and with other claddings, any secondary defense methods, disposal of moisture that does penetrate, and exposure and durability considerations.
It is hoped that the result of this and further studies will be a Verification Method for the building envelope useful for manufacturers to predict that their product will comply with the code and for designers who are dealing with unique situations to prove compliance without costly testing.