Leaky-building guidelines

By ANNE GIBSON and ANDREW LAXON

Detailed rules designed to make houses more leakproof are to be announced by the Building Industry Authority today.

The standards are expected to approve certain brands of monolithic cladding - the single-sheet exterior wall systems blamed by some in the industry for allowing leaks in the past.

Other brands will not be listed but builders will still be able to use them if they can prove they meet the standards.

The announcement is the second stage in a crackdown on building standards intended to stop the leaky-building crisis.

Last December the authority ruled that treated timber had to be used in those parts of a building most vulnerable to leaks and rot.

Authority chairman Barry Brown, chief executive John Ryan and technical adviser Adrian Bennett will present the new building standards on stopping external moisture getting into buildings.

Last June, the authority signalled its intention to change its "acceptable solutions" requirements, which set out design rules for new buildings. If these requirements are followed, a building is deemed to comply with the Building Code and gets a code compliance certificate.

The standards are not compulsory - builders and designers can choose to deviate from them but must provide evidence that the building is up to standard before a compliance certificate is issued.

The authority's former chief, Richard Martin, said last June the review would give more detail on prescribing how certain building materials, particularly monolithic claddings, should be used to prevent buildings from leaking.

But the changes are not popular with all factions of the sector.

Building disputes arbitrator Geoff Bayley said last year that he and engineer Dr Kelvin Walls had calculated a $10 billion price rise in house construction in the next two decades as a result of introducing more treated timber and ventilated cavities to plastered houses.