Douglas Fir is back

  • 8 April 2011
  • Home Energy Centre
Waimea’s battle to bring Douglas fir back finally pays off

Waimea would like to say a big thank you to everyone that submitted in support of untreated Douglas fir staying in the building code!

DBH received 237 submissions
– an unprecedented number – and 75% of them were in favour of untreated Douglas fir.

What are the changes?

Douglas fir – the chemical free option
  1. Untreated Douglas fir can be used for all the framing in traditional low risk houses (e.g., houses that are one or two storeys, and have eaves and cavity walls). Click to view the full description of low risk.
  2. DBH confined the used of Douglas fir to low risk designs primarily for reasons of simplicity. This means that alternative solutions will be needed to use untreated Douglas fir in medium and high risk buildings and in commercial buildings.
  3. Untreated Radiata is no longer allowed.

Radiata and Douglas fir – treated options
  1. Boron treated H1.2 Radiata Pine and Douglas fir are now allowed to be used for all elements inside the building envelope!
  2. There is no longer a requirement to use H3.1 for certain elements (e.g., flat roofs). This is because the scientific research confirms that boron H1.2 performs just as well as H3.1 LOSP in enclosed framing applications.
  3. H3.2 must be used for cantilevered deck joists and framing.
  4. Cavity battens must be H3.1, but we will continue to recommend H1.2 boron as an alternative solution for cavity battens.

Our initial take on the changes

Waimea has been struggling since 2003 to get untreated Douglas fir back in the building code, so we are delighted that DBH has recognised that Douglas fir has more resistance to decay than Radiata Pine.

It is fantastic that the red tape has been removed and it will now be much easier to use untreated Douglas fir in low risk buildings. It’s a bit of a shame that untreated Douglas fir has been ring-fenced to low risk designs only, but we will continue to work with local councils and specifiers to use alternative solutions where they are appropriate for medium and high risk houses and commercial buildings.

We’ve very supportive of DBH’s move to allow H1.2 boron treated Douglas fir and Radiata Pine to be used for all framing inside the building envelope, except cantilevered decks, which must be H3.2. This means that there is no reason for specifiers to “over-specify” treatment levels any more. They can be confident in the H1.2 boron treatment.

We would have preferred it if DBH had removed the option of using higher hazard classes (H3.1 and H3.2) inside the building envelope. These treatments are designed for outside uses (weatherboards, decks etc) and it overkill to use these inside the building envelope.

We’ll still be offering our timber design advisory service to help clients maximise the use of untreated Douglas fir (using acceptable and alternative solutions) and minimise the overall treatment level.

Find out more

Check out the Amendments to B2 Durability: Download PDF

Check out the issues raised in consultation:

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