Dry home costs $2500 more

By ANNE GIBSON

New building standards to stop leaks will cost about $2500 a house - but the changes are predicted to save about $800 million in repair bills.

As a torrential downpour exhausted itself over Auckland yesterday, Building Industry Authority chairman Barry Brown launched changes to the Building Code, to outlaw some materials and practices that have contributed to homes rotting.

The changes are a response to the leaky building crisis, which some experts believe could affect tens of thousands of houses built in the last decade.

The new rules, covering a range of common building practices, govern construction of timber-framed buildings up to three levels high. They come into force from next February 1 and add more detail on how buildings should be designed and built to stop them leaking.

People building under the existing rules have until January 2006 to finish work and get their buildings signed off by a council inspector.

But the authority is "strongly encouraging" people who are designing houses now to use the new rules.

Mr Brown cited a study by the Institute of Economic Research showing the changes would add just $500 to the cost of a simple brick house but up to $5000 for others.

"The average cost increase over all new houses is around $2500," he said, but an apartment would cost an extra $3000 to build.

The study showed a net benefit of $800 million resulting from the changes over the next 25 years, largely as a result of not having to repair leaky buildings, he said.

The authority has particularly targeted houses of more than one level, built in exposed areas with a monolithic cladding (exterior wall surfaces made of materials such as stucco and fibre-cement).

Other aggravating features are a flat roof, no eaves, complicated shapes and decks or balconies.

Houses least at risk are single-level brick homes with a pitched roof, simple design, in a sheltered spot without decks or balconies.

The more stringent rules will be used on new houses deemed high-risk.

Adrian Bennett, seconded to the authority from the Building Research Association, said an indication of the extent of the changes was that the Building Code's acceptable solutions document had ballooned from 12 pages to 150.

The old rules covered just three types of house cladding: brick veneer, weatherboards and stucco. The new rules add fibre-cement weatherboards, profiled metal, fibre-cement sheet, plywood and polystyrene.

The rules cover cavity walls, roofing, sealants, flashings on doors and windows, pipe penetrations through roofs, gutter and wall junctions, and membrane roofs and decks.

The rules set out how to build drained cavities to allow water that penetrates a cladding to drain away.

They specify methods for installing certain types of windows to minimise the risk of leaks, how to waterproof solid decks, how to design and build the junctions between roofs and walls, how to design and install flashings and the training required for people who install certain types of wall or roof claddings.

Placemakers general manager of marketing, Andrew Simcock, said the change would bring consistency and clarity to building standards.

THE CHANGES

The new rules set out how to:

Build walls with gaps so any leaks can drain away.

Install leak-resistant windows.

Waterproof solid decks.

Design and build junctions between roofs and walls.

Design and install flashings (protective coverings).

Ensure only properly trained people install the more complex claddings.

THE COSTS

New brick house: $500.

Other new homes: Up to $5000.

Average extra cost: $2500.

Estimated savings on leaky home repairs: $800 million.

WHO'S AFFECTED

Highest-risk homes: Multi-storey, exposed to weather, monolithic cladding (eg stucco, fibre-cement), flat roof, no eaves, complicated design, deck or balcony.

Lowest-risk homes: Single-storey, brick, pitched roof, simple design, sheltered, no deck or balcony.