This statement provides information on the expected durability performance of Wespine Blue treated timber products for building regulators, designers and homeowners. This statement has been prepared in response to publication of the Guideline on Durability in Buildings by the Australian Building Codes Board.
Wespine Blue is a new affordable, in-line treatment system that provides effective protection to pine framing timber against termites (excluding Mastotermes darwiniensis) and European House Borers under conditions which are described as H2F according to AS1604 (dry, above ground, protected from weather and moisture).
The treatment uses a synthetic pyrethroid in a waterbased solution. Synthetic pyrethroid insecticides such as permethrin and bifenthrin are highly repellent and contact is toxic to termites and European House Borers. The Wespine Blue system places the treatment barrier around the outside of the wood where it is most needed. By ensuring an adequate envelope, the insecticidal protection will be retained over the long term.
Seasoned softwood is an ideal timber for a wide range of building applications, including all roof, wall and floor framing. Specifically, these are situations where the timber is protected from direct weather and moisture but may be subject to termite or borer attack. Wespine Blue treated softwood is intended to provide a deemed-to-satisfy termite or borer resistant construction by rendering the structural timber termite resistant in accordance with AS3660.1 for areas not subject to Mastotermes darwiniensis (south of the Tropic of Capricorn). Although termite and borer resistant construction using preservative treated or naturally termite/borer resistant timbers for all structural elements below the termite barrier is deemed to- satisfy, termites and borers are not prevented from entering the house envelope. Wespine recommends good building practice such as whole-of-house protection to mitigate unwelcome access by termites or borers. Whole-of-house protection can take the form of physical or chemical barriers, together with regular inspections and maintenance. H2 treated structural framing and whole-of-house protection provides a comprehensive solution to the termite or European House Borer hazard, and peace of mind for the building owner.
Specific Service Conditions
Service conditions for Wespine Blue treated softwood framing are internal, above ground, dry, and potentially subject to attack by termites or borers south of the Tropic of Capricorn in Australia. In addition to these standard service conditions, building timber may be subject to temporary weathering for a maximum period of up to 3 months while material is in storage and the frame is in construction. These service conditions correspond to a Hazard Class 2F environment as defined in AS1604.1. During this period the Wespine Blue should be kept clear of the ground and stored so that it remains straight and true.
2mm from all faces
All timber sizes up to 240mm finished width and 45mm finished thickness.
Retention (analytical zone)
Minimum of 0.02% mass/mass bifenthrin in the outer 0 to 2mm zone.
Coptotermes spp, Schedorhinotermes spp, Nasutitermes spp, Heterotermes s
Region of use
South of Tropic of Capricorn
Proposed Brand Designation
H2 – F
The registered label calls for a bifenthrin loading of a minimum 0.02% m/m in the outer 2mm. For Pinus radiata 2mm penetration all round regardless of heartwood or sapwood. Analysis of pine treated with Wespine Blue has shown a well defined envelope to a depth typically of 2mm in softwood. Osmose Australia Pty Ltd has received APVMA (previously NRA) approval for Wespine Blue as a timber preservative for protection of pine framing timber from termite and borer species south of the Tropic of Capricorn (areas not subject to Mastotermes darwiniensis). Note: Wespine Blue treated timber would be deemed not to be termite resistant north of the Tropic of Capricorn.
Design and Detailing
Good design and detailing practice should ensure that the building is protected from moisture and not exposed to unnecessary decay hazard. Guidelines for good building practice are given in TRADAC Technical Data Sheet 10 "Recommendations for the use of seasoned softwood framing".
Standard steel nails will be adequate for all fixings in terms of durability.
Ventilation and Ground Clearance
Roof, sub-floor and external wall cavities should be ventilated. Minimum ventilation and clearance requirements for sub-floors should be provided in accordance with the Building Code of Australia (BCA).
Onsite Handling and Weather Exposure
Wespine Blue treatment will not be significantly impaired by normal exposure and handling prior to and during construction. Do not store Wespine Blue treated timber in ground contact.
Quality of workmanship in all building construction is necessary to ensure the satisfactory performance of the construction for the long term.
Regular building inspections for termite or borer activity and maintenance of the inspection barrier are required under AS3660.1. Maintenance and inspection to ensure that water leaks or failure of weather tightness do not expose the Wespine Blue treated timber, untreated timber, and other construction materials to degradation from excess moisture or decay hazard.
Assessment of Durability
The durability of Wespine Blue treated timber has been assessed on the basis of published references, together with established historical and performance data. A number of studies have shown that in dry weather protected building applications, synthetic pyrethroids insecticides have a long residual life in timber (Orsler and Stone IRGIWP32881984, Berry and Read IRG IWP/1569-92, Powell and Robinson J. of Economic Entomology October 1992). These references indicate a projected ultimate service life in timber of up to 50 years depending on the conditions. In addition the exposure to weathering during the construction phase needs to be considered. Framing timber can typically be exposed to sunlight and rain for up to twelve weeks during construction.