14 March, 2011
Simplifying Timber Treatment
Treatment to protect timber from decay and insects will be simpler from 4 April, Building and Construction Minister Maurice Williamson announced today.
“This will make it easier to build safe, durable homes cost effectively while maintaining, and in some aspects improving, protection against fungal decay for timber-framed homes.
“It follows extensive work with the timber and building industry over the past two years and submissions showed a high level of support for the proposals,” Mr Williamson said.
A transition period will let industry adjust to the change which becomes fully effective on 1 July.
The Minister said the key change is that there will be a single class of timber treatment, H1.2, for almost all enclosed timber framing.
“Currently there are as many as four different classes of timber, including untreated timber, used to frame a house. This is complex, costly and can lead to mistakes on site.
“For example, timber framing in the external walls of a house must be treated but framing for internal walls can be untreated as can roof trusses. Under the new system H1.2 will be used for internal walls and roof trusses too.”
Mr Williamson said untreated Douglas fir could be used, but only for houses of a defined low-risk design. “Untreated Douglas fir is more resistant to decay than untreated radiata pine, but less than H1.2 treated timber.”
The Minister said this was the first of a number of changes to the Building Code and associated documents that are likely to be rolled out this year.
“My goal is an efficient, productive sector that stands behind the quality of its work and ‘builds it right first time’. We need to simplify and clarify the Building Code to make it easier for everyone to understand how to comply and to design and construct buildings that are safe and durable for New Zealanders.”
- Timber treatment class H1.2 can be used for almost all enclosed framing. Currently there are as many as four different classes of timber used within a house including untreated timber.
- People who don’t want to use treated timber can use untreated Douglas Fir but only in low-risk houses of simple design. Untreated Douglas Fir is more resistant to decay than untreated radiate pine, but not as resistant as H1.2 treated timber.
- Timber treatment class H3.2 must be used for cantilevered deck joists and framing. This is a prudent safety precaution as cantilevered decks depend more critically on the strength of the timber to prevent collapse.
- The current system is complex, costly and can lead to mistakes on site. The new system is: simpler and clearer; maintains and in some aspects improves protection against decay for consumers; reduces inventory costs; reduces the risk of mistakes on site.
- The Department of Building and Housing has worked closely with the timber and building industry to identify ways to simplify and clarify the system, improve quality assurance and maintain the current level of protection.
- There were 237 submissions on the proposals. Seventy-five percent supported a single hazard class for framing timber; more than 90% agreed that H1.2 provides adequate protection from decay for framing which is enclosed; about 75% supported the use of untreated Douglas Fir for simple designs in low risk situations.
Why allow the use of untreated Douglas Fir?
- Douglas Fir is more resistant to decay than untreated radiata pine and is suitable for low-risk houses of simple design. The Department of Building and Housing has defined what is considered a low-risk design.