Double worries in timber homes

By ANNE GIBSON

The spectre of weaker wood used in new home construction, combined with leaking and rotting timber-framed houses, is haunting industry experts.

Last month, the Building Industry Authority said it would start an investigation into rotting, leaking new houses.

At the same time, a Wellington conference heard how faster-growing radiata pine trees are resulting in weaker wood.

Solid timber housing manufacturer Lockwood Homes - which has built about 30,000 houses - has backed the investigation into leaking and rotting new buildings.

The authority, the Government body responsible for building controls, said on March 25 that several industry groups had reported many leaking and rotting houses.

Chief executive Bill Porteous said an independent team of three would investigate the reports. The Building Research Association has also formed a group called the Overview Group on Weather-Tightness.

"The authority has asked the group to obtain evidence to show how widespread and how big the problem is and to identify all likely causes," he said.

Evidence that housing timber was getting weaker was presented on the same day at the annual conference of the Institution of Professional Engineers in Wellington.

Radiata pine trees are maturing in just 25 years when they used to take 35 years.They are producing timber that is now more variable in its strength, especially on the outer parts of a trunk, says Standards New Zealand project manager Ian Brewer.

Porteous said he had yet to hear of any links made between weaker timber and the decay problem in new houses. "

Lockwood executive chairman Joe La Grouw said poor design and bad workmanship in some conventionally built untreated timber homes was the primary cause of the problems. But publicity about the issue had created unnecessary concern for all those who lived in timber homes.

"Some modern homes are built so tightly sealed that they cannot breathe to allow moisture to escape, so it simply builds up inside the building until it rots the surrounds," La Grouw said.

"Family homes are the single biggest investment for most people and they are entitled to expect that a home built to national standards will not fall apart in a couple of years or less.

"The Building Code requires buildings to be weather tight, but permits the use of untreated timber in homes which are sometimes thrown up by builders who lack the necessary skills and experience. The code should be amended to correct this anomaly, and inspection standards should be lifted to protect the public."

The Building Research Association has undertaken extensive research and industry liaison on the problem of leaky, rotting buildings. It spearheaded an industry initiative with its Weathertight Buildings Project on how to resolve the problems and appointed Adrian Bennett its weathertight buildings manager. Its dedicated website www.weathertight.org.nz gives details of the work which is going into the industry, including research and education.

Lockwood

Building Industry Authority

Weathertight Buildings Project

Building Research Association of New Zealand