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Published in April 2011
ISBN: 978-0-478-34383-0 (print)
ISBN: 978-0-478-34384-7 (web)

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Pink is tough - A quick guide to timber treatment for enclosed framing

This document is issued as guidance under section 175 of the Building Act 2004.

On this page:

A new timber treatment system for Acceptable Solution B2/AS1:

  • tough against fungal decay and insect attack
  • simpler and easier to use
  • protects framing from decay
  • time and cost effective.

Timber treatment in Acceptable Solution B2/AS1 has changed to a new, simpler system:

If you are using the Acceptable Solution to demonstrate compliance with the Building Code, H1.2 is now required for nearly all radiata pine and Douglas fir enclosed timber framing.

Diagram showing types of timber framing for use with H1.2

What's new with timber treatment?

The Acceptable Solution B2/AS1 has changed. The timber treatment hazard class H1.2 is now required for radiata pine and Douglas fir timber in buildings, where it is protected from the weather (ie, enclosed timber framing). Consult the tables in this booklet for the few exceptions to H1.2 treatment.

Why H1.2?

Research shows that H1.2 gives framing timber good protection from decay. H1.2 boron treatment is colour-coded pink.

How can I be sure my timber framing complies with the Building Code?

The changes in this booklet outline one way to comply with the New Zealand Building Code durability clause B2. However, the booklet is only a quick guide, so consult Acceptable Solution B2/AS1 for full details.

Why continue to treat timber?

Timber must be adequately protected against damage from fungal and insect attack so that buildings are durable and comply with the Building Code. The new system improves the overall level of protection against decay.

What about other species of wood for framing?

For other species of wood and engineered wood products (such as LVL and Glulam), the Acceptable Solution does not change. For information on other species which can be used under the Acceptable Solution, consult NZS 3602:2003 Tables 1 and 2.

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The Building Code and Acceptable Solution B2/AS1

This booklet is a quick guide to timber treatment changes in the Acceptable Solution B2/AS1. Designers should consult B2/AS1 itself for more information on timber treatment.

The Department of Building and Housing's Acceptable Solution B2/AS1 can be found in the B2 (Durability) Compliance Document at: www.dbh.govt.nz/compliance-documents

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Glossary

Building Code and B2

The Building Code sets out performance standards that building work must meet. It has 35 technical clauses covering requirements such as managing external moisture, structure and ventilation. Clause B2 is the technical clause for durability and includes timber treatment. It sets out the durability requirements for all building elements.

Acceptable Solution

An Acceptable Solution details one way to comply with the relevant part of the Building Code. If you follow this method, your building work will meet that part of the Building Code. B2/AS1 is an Acceptable Solution for clause B2 (Durability) of the Building Code.

There can be ways of complying with the Building Code other than through an Acceptable Solution – these are often called alternative solutions.

H1.2

This is a hazard class for timber treatment. A hazard class defines the risk and the level of timber treatment, as specified in NZS 3640 and NZS 3602.

Building Envelope

This describes the exterior surfaces (wall cladding, roofing, windows and doors) of a building.

For full details check B2/AS1

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Overview of Timber Treatment for Radiata pine and Douglas fir

For full details check B2/AS1

Where timber treatments are used
Level Species Building Element
 
Floor framing protected from weather but exposed to ground atmosphere
H1.2 Radiata pine

Douglas fir

Jackstuds, subfloor braces, wall plates, floor joists to the subfloor, blocking, walings and battens, nogs and diagonal boards
H1.2 Radiata pine

Douglas fir

Interior solid wood flooring for ground floors
Enclosed roof framing and trusses
H1.2 Radiata pine

Douglas fir

Sarking and framing not protected from solar-driven moisture through absorbent cladding materials
H1.2 Radiata pine

Douglas fir

Enclosed flat roof framing and associated roof members
H1.2 Radiata pine

Douglas fir

Enclosed skillion roof framing and associated roof members
H1.2 Radiata pine

Douglas fir

Valley boards and boards supporting flashings for box gutters, roof penetrations and upstands to roof decks
H1.2 Radiata pine

Douglas fir

All roof trusses, including gable end trusses, roof framing, ceiling and eaves framing, purlins and battens
Enclosed wall framing protected from the weather
H1.2 Radiata pine

Douglas fir

Framing and other members within or beneath a parapet
H1.2 Radiata pine

Douglas fir

Framing and other members within enclosed decks or balconies (see H3.2 for cantilevered decks)
H3.2 Radiata pine Framing and other members within enclosed cantilevered decks (including joist trimmers, nogs and blocking)
H1.2  Radiata pine

Douglas fir

Framing and other members supporting enclosed decks or balconies (including for cantilevered decks)
H3.1 Radiata pine Battens used behind cladding to form a cavity (H3.1 treatments can be either solvent-based or boron. H3.1 boron treatments supplied grey primer-painted)
H1.2 Radiata pine

Douglas fir

All other exterior wall framing and other members including exterior and boundary joists
Internal Wall Framing
H1.2 Radiata pine

Douglas fir

Internal walls
Mid-floor framing
H1.2 Radiata pine

Douglas fir

All mid-floor framing, including boundary joists, ceiling framing and ceiling battens and double top plates
Interior flooring
H1.2 Pinus species

Douglas fir

Interior flooring
Other framing
None Radiata pine
Douglas fir
Wall framing and roof framing (including trusses) protected from the weather, in unlined and unoccupied farm buildings and outbuildings, except buildings with high internal humidity, such as saunas, spas etc
H3.2 Radiata pine Framing exposed to the weather and above ground
H4 Radiata pine Framing, such as fence posts and landscape timbers, that is exposed to the weather and is in contact with the ground
H5 Radiata pine  Framing, such as house piles, poles and crib walling, that is exposed to the weather and is in contact with the ground.

Note 1: For structural use of other species, refer to NZS 3602:2003 Tables 1 and 2.

Note 2: For non-structural use of radiata pine, Douglas fir and other species, refer to NZS 3602:2003 Table 3.

Note 3: A higher treatment level also satisfies the level specified in this table. 

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Untreated Douglas fir

The new timber treatment system for Acceptable Solution B2/AS1 allows untreated Douglas fir to be used in houses of a defined low-risk design. Research shows that Douglas fir resists decay better than untreated radiata pine, but not as well as H1.2 treated timber.

Untreated solid Douglas fir framing can be used for a house of no more than two storeys (as defined in NZS 3604), that is designed and constructed to NZS 3604, if ALL the following low-risk conditions are met:

Low-risk house conditions
is a standalone, single household unit of no more than two storeys (as defined in NZS 3604), that is designed and constructed to NZS 3604
AND
is situated in wind zones no greater than ‘high’ as defined in NZS 3604
AND
has a building envelope complexity no greater than ‘medium risk’, and a deck design no greater than ‘low risk’, as defined by the risk matrix in the Acceptable Solution E2/AS1
AND
has drained and vented cavities complying with E2/AS1, behind all claddings
AND
uses roof and wall cladding systems and details meeting E2/AS1
AND
has a risk matrix score of no more than 6 on any external wall face, as defined in E2/AS1
AND
has a simple pitched roof with hips, valleys, gables, or mono pitches, all draining directly to external gutters*
AND
has a roof slope of 10° or more
AND
if it has a skillion roof, the roofing material is corrugated iron or concrete, metal or clay tiles for adequate ventilation
AND
has eaves 450mm-wide or more for single-storey houses, and eaves 600mm-wide or more for two-storey houses.

* The roof does not have internal or secret gutters, concealed gutters behind fascias, or any roof element finishing within the boundaries formed by exterior walls (eg, the lower ends of apron flashings, chimneys, dormers, clerestories, box windows).

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When does the new system start?

From 4 April 2011 to 30 June 2011, both the previous B2/AS1 (amendment 6) and the new B2/AS1 (amendment 7) can be used as an Acceptable Solution for consenting purposes.

From 1 July 2011 onwards, only the new B2/AS1 can be used as an Acceptable Solution.

Know the new system - and frame it right first time.

Post-it notes with new system dates

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Safety and health

Timber treatments generally consist of chemicals that need to be handled safely and appropriately. Important measures to take when using treated timber, especially hazard classes H3 and above, are:

  • reduce contact by wearing gloves, goggles and a dust mask
  • don't burn off-cuts or cook with them
  • dispose of waste in an approved landfill
  • wash your hands before using the toilet, smoking or eating
  • wash work clothes separately
  • ventilate work spaces as much as you can
  • working with solvent-damp timber is not advised, solvent-damp timber should be allowed to properly dry off before use.

Note: Boron has been used commercially as a timber preservative in New Zealand since the 1950s, with no known health issues for timber users or building inhabitants. 

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Reference diagrams

Roof framing: general


New B2/AS1

  • H1.2 Radiata pine
  • H1.2 Douglas fir
Reference diagram 1. Roof framing: general.

Roof framing: solar driven moisture


New B2/AS1

  • H1.2 Radiata pine
  • H1.2 Douglas fir
Reference diagram 2: Roof framing: solar driven moisture.

Roof framing: roofs under 10°


New B2/AS1

  • H1.2 Radiata pine
  • H1.2 Douglas fir
Reference diagram 3: Roof framing: Roofs under 10 degrees.

Roof framing: Skillion roofs


New B2/AS1

  • H1.2 Radiata pine
  • H1.2 Douglas fir
Reference diagram 4: Roof framing: Skillion roofs

Roof trusses:

New B2/AS1

  • H1.2 Radiata pine
  • H1.2 Douglas fir
Reference diagram 5: Roof trusses

Valleys, box gutters, purlins, battens, etc:


New B2/AS1

  • H1.2 Radiata pine
  • H1.2 Douglas fir
Reference diagram 6: valleys, box gutters, purlins, battens, etc

Enclosed decks:


New B2/AS1

  • H1.2 Radiata pine
  • H1.2 Douglas fir
Reference diagram 7: Enclosed decks

Cantilevered enclosed decks:


New B2/AS1

Balustrade:

  • H1.2 Radiata pine
  • H1.2 Douglas fir

Cantilevered deck framing:

  • H3.2 Radiata pine
Reference diagram 8: Cantilevered enclosed decks

Wall framing single-storey:


New B2/AS1

  • H1.2 Radiata pine
  • H1.2 Douglas fir

Or house of low-risk design:

  • Untreated Douglas fir
Reference diagram 9: Wall framing single-storey

Wall framing two-storey:


New B2/AS1

  • H1.2 Radiata pine
  • H1.2 Douglas fir

Or house of low-risk design:

  • Untreated Douglas fir
Reference diagram 10: Wall framing two-storey

Eaves, trimmers, parapets, furring, enclosed columns, etc:


New B2/AS1

  • H1.2 Radiata pine
  • H1.2 Douglas fir
Reference diagram 11: Eaves, trimmers, parapets, furring, enclosed columns, etc

Enclosed exterior elements:


New B2/AS1

  • H1.2 Radiata pine
  • H1.2 Douglas fir
Reference diagram 12: Enclosed exterior elements

Enclosed sub-floor framing:


New B2/AS1

  • H1.2 Radiata pine
  • H1.2 Douglas fir

*DPC

  • Concrete piles – all cases
  • Timber piles – between 150mm and 300mm above ground
Reference diagram 13: Enclosed sub-floor framing

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