TimberSaver Boron Treated Framing: What it is, the Department’s accreditation and its conditions of use
What is TimberSaver boron framing timber?
The product is treated kiln-dried radiata pine framing in sizes up to 290 x 45 mm. It is produced with a distinctive orange colour and imprinted at 1.5 metre centres along one face or edge with the words 'TIMBERSAVER BORON' and identification of the treatment plant (eg, TDC Sawmills).
The preservative used is a liquid boron formulation, known as PROTIM TimberSaverTM produced by Osmose New Zealand (see contact overleaf).
The treatment process is a departure from the usual 'full sapwood penetration' processes used in other boron treated framing described in NZS 3640: 2003 Chemical Preservation of Round and Sawn Timber. The preservative, in a glycol solvent formulation, is deposited in at least the outer 3 mm of the timber and is designed to be carried into the timber with water in the event the timber becomes wet.
The preservative formulation is sprayed or dipped onto the timber at a prescribed application rate and resists limited exposures to both fungal decay and insect attack.
The timber can be safely handled with the same precautions recommended for most framing timber. The TimberSaver preservative is a legal existing substance under the Hazardous Substances and New Organisms Act 1996.
Does it comply with requirements of the New Zealand Building Code?
The product, as produced at certain nominated treatment plants, is accredited for use by the Department of Building and Housing. This means it is deemed to comply with particular performance requirements of the Building Code, provided it is used as stipulated in the Certificate of Accreditation - in other words, provided it is used strictly in accordance with the appropriate Appraisal.
There are Appraisals for product produced at each of the nominated treatment plants, which can be downloaded.
The product is accredited for use where H1.1 and H1.2 timber is required under NZS 3602: 2003.
The Appraisal is the key document and the Department's endorsement is conditional on the Appraisal being followed. If you intend using the product, ensure you download the Appraisal and are fully conversant with its scope and conditions of use.
Exposure to the weather
A particularly important construction phase requirement is that the product is not exposed to the weather for longer than 2 months, including during storage, transport and construction. If a building project is unable to have the framing closed in during this period, other more suitable types of timber framing must be used.
This 2-month exposure period includes any time that the product is left exposed to the weather off-site, in such locations as the timber merchant's or fabricator's yard. Timber merchants and fabricators need to be aware of this requirement and, if asked, provide evidence as to how the product has been stored while in their care.
Who specifies its use?
Designers must stipulate in building consent documentation the type and level of timber treatments and their locations. If TimberSaver boron treated framing is to be used, it must be specified by the designer and approved by the building consent authority prior to the work proceeding.
As the product has been accredited for use by the Department, the building consent authority must accept its use, but only when used within the scope and conditions of the appropriate Appraisal.
How must it be used on site?
TimberSaver boron treated timber is similar to most treated framing timbers in the way it must be protected after treatment, and before it is closed in on site. Builders must organise the sequence of work carefully so that timber frames in general are stood in place as soon as they are delivered or made up on site. The work must then proceed quickly to protect the frames from the weather.
Most preservative treatments for framing timber are 'non-fixed' in that they will leach with prolonged exposure to the weather. Where TimberSaver boron treated framing is used, exposure to the weather is strictly controlled by the conditions in the Appraisal.
Particular conditions of use of TimberSaver boron treated timber as noted in the Appraisal include that the timber:
- must be stored under cover and clear of the ground
- must not be exposed to the weather for longer than 2 months, including all periods of storage, transportation and construction
- must have cuts at angles greater than 45 degrees from square and bored holes greater than 25 mm diameter, liberally coated on site with brush-on PROTIM FrameSaver
- must be site treated as described above where machining, rebating, notching, ripping or planing of surfaces occurs
- can only be used where the in-service moisture content is 20 percent or less and the timber is not exposed to the elements or subject to regular wetting.
Osmose New Zealand provides safety data sheets for the product entitled PROTIM TimberSaver treated radiata pine, dated July 2003, which are available at the point of sale or directly from Osmose New Zealand. Phone 0800 78 70 70.