Poster puts leaks in place

By ANDREW LAXON

Simple building and design improvements can save your new home from leaks and rot, says the Building Research Association.

Experts believe thousands of homes built in the past decade have leak and rot problems, with one in 10 new homes potentially at risk and a national repair bill that could easily top $1 billion.

In April, an independent inquiry for the Building Industry Authority urged immediate action to solve the problem, which it blamed on technical issues and shoddy building practices.

Now the association, which advises the building industry, has produced a poster for builders, councils and homeowners which shows 10 areas of risk and how to reduce them.

It says leaks are most likely to happen in houses on elevated or exposed sites with strong winds.

Multi-storey buildings with complex designs are susceptible, especially if they do not have eaves to deflect rain from walls.

Other potential design problems are parapets and balconies, which can allow water to slip through gaps.

Most problems occur with one-piece outside walls (referred to as "face-sealed cladding systems" in the poster) such as fibre cement, stucco or polystyrene, if they do not have gaps between the timber framing to allow water to drain away.

The association advises homeowners and builders to use H3 treated timber - which protects against "moderate decay" and is the standard already required for decks - in all high-risk areas to stop rot spreading if leaks do occur.

The authority, which oversees the Building Code, also plans tougher temporary regulations requiring H3 timber to be used on exterior wall frames and wall frame bottom plates unless builders can come up with an equally waterproof alternative.

Many of the association suggestions involve using metal or plastic flashings instead of sealants to waterproof joins between materials - a point stressed as crucial in the independent report to the authority.

Association weathertightness manager Adrian Bennett, who also chairs the industry's steering group on the issue, said most homeowners would be familiar with metal or plastic head flashings at the top of aluminium windows.

Other examples were roof flashings around chimneys and sill flashings under windows or on balconies.

He said homeowners and builders often filled these gaps with sealants because it was cheaper and looked better than a strip of metal or plastic.

But although some sealants were good quality, they had to be applied very carefully to avoid leaks.

* For a copy of the poster ring the Building Research Association on 0900 59090. Information is also available on the website Weathertight or in Build magazine.