Philip O'Sullivan: Boron timber treatment justified - 40 years on

Stephen Jacobi, of the Forest Industries Council, says the case for mandatory use of treated construction framing has not been proved. What he doesn't say is that the success of radiata pine as building framing is based on boron treatment over many years.

In the 1930s New Zealand was faced with a dwindling supply of durable native building timbers. Ways had to be found to use less durable wood, and especially the pine forests.

A research programme by Ken Harrow and another young scientist, Don Spiller, remains impressive. They collected samples of decayed timber and wood-boring insects, breeding and individually sexing 500,000 borer beetles. A large range of chemicals and methods were considered.

Tens of thousands of timber samples were checked for leaching, decay and insect resistance. A trial building was constructed and pilot treatment plants were established in Rotorua and Whakatane.

The pair were searching for a treatment that would be effective, economical and safe. They eventually chose boron. A 1952 Government-appointed committee of inquiry supported boron treatment.

After 40 years with boron and only five years without, we now know that Ken Harrow and Don Spiller got it right.

So what went wrong? In 1986 Standards New Zealand brought our treatment standards into line with those of Australia. From then on framing timbers required only insect protection.

The standard specifying timber for building was further revised in 1995. For the first time since 1952, untreated pine framing was permitted.

Forest Research opposed the move because it considered the evidence inadequate and the risks too high. It's view has not changed. Builders were persuaded to change from traditional wet boric to kiln-dried, untreated pine.

To some extent the success of boron as a fungicide had lulled the industry into a false sense of security. Poor practices were rife. If leaks occurred, the problem could be fixed and the timber left to dry out.

With the demise of boron, the more dangerous brown rots took hold. Even with minor leaks, sealed wall cavities are ideal for these rots to flourish.

The leaky building syndrome led to the Hunn report, which recommended our building methods and materials become more robust. To achieve this, claddings must be able to drain and ventilate so if water does get in, it can escape before damage is done.

Secondly, the framing needs to be sufficiently durable so it will not suffer rampant rot before it dries out or the building is repaired.

Why treat all the framing? We have tried mixing treated and untreated timber on site. Invariably the wrong timber is used in places. There have been a number of instances where already rotten timber was delivered to site. A major supplier had to condemn many packets of timber because they had rotted in its yard. It was then sold as boxing, but I wonder how much ended up in houses.

The timber industry forgets that roofs and gutters leak, as do showers, laundries, kitchen appliances and plumbing fittings. The rules need to be simple to be effective.

New Zealand had been praised in North America as the only sensible country in the world because we treated our timber framing. The Americans hail boron as the "green treatment" because it is so safe.

In Britain, framing timber is treated against rot for insurance purposes, although most of its timber-frame buildings are brick-clad. Should we turn to Asia for our building standards?

I have spoken to many in the timber industry who are dismayed at what has happened. They understand the vulnerability of untreated pine and the realities of building sites. Such people seem to be missing from the higher echelons of the industry.

Perhaps Mr Jacobi should look at our own market, where many developers are turning from timber to concrete construction. Times may be tough, but they will get tougher unless his industry puts vision and integrity ahead of short-term profit.

He claims 1 per cent of houses built since 1992 are affected. What expertise or experience does his council have to make this claim? A Unitec report, commissioned by the Building Industry Authority, found half of the houses in the survey built since 1990 were affected by cladding leaks.

Mr Jacobi fails to consider the huge repair costs and emotional trauma suffered by the owners of leaky homes. A few per cent added to the initial cost would be well worth the peace of mind.

* Philip O'Sullivan, an Auckland property consultant, is responding to Stephen Jacobi's view that Building Industry Authority proposals are unnecessarily tough on the forest industry.