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Termite Issue
Concrete Capping
The Queensland Building Code amendments in relation to the termite issue included special provisions for chemical perimeters. A copy of the Building Codes Queensland summary of those requirements follows. A major part of the amendments was that the chemical perimeters were required to be reticulated, to have a suitable material installed, and also to have a concrete mowing strip placed over them to prevent disturbance by the homeowner and conditions. A clause, "Other means of protecting the barrier can be approved as an alternative solution provided it can be demonstrated they satisfy the performance criteria of the BCA".
These pictures were taken at a home on Brisbane's Northside, in a major estate built by the one builder. The homes are of a waffle pod slab design, and a reticulation system and Biflex chemical barrier have been installed to the slab penetrations and the exterior perimeter. Even though construction was started well after the Queensland Building Code amendments came into force, no concrete capping has been installed, and it would appear they are relying on the notice below to comply with the performance criteria clause of the Building Code amendments. It's also interesting to note that the life expectancy section of the treatment notice hasn't been filled in. Biflex applied at it's higher application rate has a labelled expected protection of at least 10 years. It'll also be interesting to find out how often the residents will be asked to replenish the termite barriers here, and at what cost.
We've contacted the Building Services Authority for their advice as to whether this complies with the performance requirements of the Building Code amendments. We can't get an answer, other than saying they have a nationally accepted "certificate of conformity". Our understanding was that the Queensland Building Code amendments were requirements that went beyond the national requirements. What happens if one home owner removes the notices from the wall, and then sells the property? What happens if the family dog digs the soil against the home? A dog can't read a sign telling it not to disturb the soil. We've got a reasonably intelligent dog (a blue/red cattle dog cross), and we can't teach it to read yet.
The Building Code amendments really have the opportunity to significantly reduce termite attack in new buildings, but we are firmly of the view they need to be policed to be effective. If certifiers are being used to sign off on systems without the concrete capping, then perhaps we ALL need to have a look at the role of private certifiers in more detail. Is it that if you are a really big builder, and a really big pest control company, you don't have to worry about minor items like Building Code requirements?
For a home owner or builder, we would encourage you to look at the Australian Building Codes Board accredited physical barriers like Granitgard and Termimesh, and the exposed slab edge. Properly installed and undisturbed, they are regarded as "life of building" products and construction methods, and should not require maintenance other than annual inspection for the life of the building. By going to chemical protection, the home owner is committed to spending more money on the maintenance of the termite protection system for the life of the building.
Reprinted below is the Building Codes Queensland summary of the amendments relating to perimeter chemical barriers.
2. Perimeter chemical barriers
Available evidence suggests that concealed termite entry is more predominant via the perimeter of the building. This may be as a result of inadequate treatment or by an unsuspecting homeowner or a contractor inadvertently breaching or bridging the barrier, for example, by placing a new garden bed over the existing barrier. In the case of slab-on-ground construction, AS3660.1 requires an under slab barrier and a barrier around the perimeter of the building to reduce the likelihood of concealed termite entry into the building.
The amendments will make it clear that in addition to any other relevant provisions of AS3660.1, a perimeter chemical barrier must be applied by excavating trenches, treating the exposed trench, backfilling with a suitable material and treating the backfill. This will provide a greater level of assurance that the perimeter barrier will be installed correctly.
Where a chemical perimeter barrier is used, the proposed amendments will include a new deemed-to-satisfy solution, which requires the barrier to be capped with a 300mm wide concrete “mowing strip”. This is to reduce the likelihood of inadvertent bridging or breaching the termite barrier. Other means of protecting the barrier can be approved as an alternative solution provided it can be demonstrated they satisfy the performance criteria of the BCA.
The different bodies above in red are links to further information on each one. Please follow the links. © Mark Porter 2002
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