There are plenty of options. For most readers of this website, this “Pre-construction” section will be too late if your house is up and lived-in. However, if you are planning or involved in the design and construction of your new home here are some things to seriously consider:
Foundations and floors. The economics of building favor the choice of a concrete slab poured onto the ground. It costs less than having a floor suspended on foundation walls, irrespective of the floor being timber or suspended concrete or something else. Suspending a floor high enough above ground level allows a person to get under to regularly inspect for the signs of termite invasion. Finding them before significant damage occurs reduces the damage and repair bill.
A NSW Forestry survey in 1958 reported a termite incidence at 3% of freestanding homes. In just 25 years (1983) the CSIRO surveyed and reported a 20 % incidence — the main difference: slab-on-ground became the norm in the early 1960s. In 2004 the CSIRO surveyed again to report a 32% incidence. This was confirmed by a report in www.archicentre.com.au of 33% of all homes inspected prior to resale showing a termite incidence. The deduction to make is that the extra expense of suspending is to a great extent compensated by the much lower likelihood of termite attack.
There is more. Once a slab floor is down you cannot re-apply chemical barriers to 100% continuity. If you go to the added expense during building to install a reticulation system for the reapplication of chemical barriers, ensure the system observes the laws of hydraulics and the liquid gets to the ends of the lines and is distributed evenly along them. Not all systems on offer do that.
The reticulation systems must, of course, be installed before the slab goes down and the installer must return to complete the job under the outside driveways and footpaths before they are laid. In this way, the barrier can be ‘topped up’ in the coming years. It is an added building expense but there is no other convenient way to replenish a chemical barrier under concrete.
Slabs do crack; just have a look at a garage floor or any other large slab of concrete. However, termites cannot get through less than 2 mm cracks and, despite the urban myths, they don’t eat their way through it. Concrete slabs must be constructed in accordance with Australian Standards (AS3660.1).
Walls and framing. Steel frames are increasingly being chosen to lower termite risk. If the usual brick veneer building has a plasterboard interior attached to steel frames, there is less enticement for termites and they certainly won’t destroy the building. Pre-treated pine frames are also being chosen. There is a range of levels of timber preservation (H1-H6); ensure you choose a level higher than against just against decay and weathering. You need the higher levels (H4-H5) to prevent termite attack (which also includes decay).
Mud-brick construction is popular in some communities for some people. It has some admirable insulation and livability values as well as cost advantages, but you need to ensure damp-courses and physical barriers are in place to stop termite access up through the middle between the mud bricks.
I cannot give you a definitive calculation on the cost of termite prevention against the cost of treating and repairing termite damage. The factors see-saw something like this: the extra cost of suspended floors with preservative treated pine framing can be weighed against the extra cost of the frames plus reticulation minus the savings from the lesser cost of slab-on-ground floors/foundations. Got it?
Pest professionals will describe instances where termites have found a way into buildings with steel/preserved frames and at the wooden smooth-edge strip that held the carpet in place and sometimes termites have just eaten the paper on the plasterboard. And yes, they have been found eating heavy timber furniture that was seldom (if ever) moved. These are all exceptional instances and less likely… but if it happens at your place, it is important.
Physical termite barriers. There are Australian Standards, and Building codes which generally defer to that Standard, which set out the minimum requirements for physical barriers.
Ant caps on top of piers or stumps were the first physical barriers. Not that termites couldn’t build a mud tunnel over them; but they couldn’t go through them. This forces the termites to construct a tunnel out and over them — out where you can see them during an inspection. There are barriers of continuous metal strips that can be set into the foundation walls protruding into the crawl space and which serve the same purpose.
Where utilities such as cables and water/drainage pipes go through the concrete slab, there are spaces big enough for a termite highway. Metal flanges, stainless steel mesh and granite or glass particles of specific size/density are used. The quality and specifications of physical barriers are to be found in AS3660.1.
Physical barriers are intended to last the life of the building, however it is still absolutely necessary to regularly inspect in case the barriers have been bridged or breached… see our section on Inspecting for Termites.
Chemical termite barriers. If you are like some of the homeowners we speak to who think the house came with a ‘certificate’ stating termite physical and chemical barriers had been completed and that you didn’t need to think about termites again — wrong! The 7-year builder’s warranty includes the pest company’s warrantee that may give you a 5-10 year period on insecticidal soil barriers — but only if you have had that company inspect annually. It’s there in the fine print. Missing even one annual inspection voids the warrantee.
The two main types of soil impregnation chemicals have a subtle difference. The original provides a deterrent chemical barrier that termites will avoid. The second has no repellent and termites will tunnel through it, but in so doing, they pick up traces of the chemical which may be transferred back to others and kill off the colony.
Up until the mid 1980s, the chemical barriers were stable and lasted an estimated 30-40 years. The replacement chemicals generally last a bit longer than 10 years, but the manufacturers and the pest managers who apply the barriers give warranties of up to ten years — and then only if you have at least annual inspections. (You can’t blame them for requiring the inspections for two reasons: barriers can be breached by human and pet intervention and, in the event of a claim, the cost of termite damage added to loss of resale value can be extremely high. The inspection means they will find damage before it becomes really expensive).
The Australian Standard AS3660.1 requires that the soil of the foundation area be treated prior to a suspended floor being laid or in the case of a slab, before the membrane is laid. It also requires that a perimeter barrier be applied before paths and driveways are put down (after the building is completed). That’s a big problem. The oversight or reluctance of builders to call back the pest manager means more often than not, the perimeter part of the barrier is not in place before the paths go down. If you are the owner/builder or even the owner keeping an eye on the building in progress, make very sure this perimeter barrier is applied because it is part of the Standard. It may only last 10+ years, but you have paid for it and should have it. If the perimeter treatment was not done, then the builder cannot claim to have constructed in accordance with the Australian Standard. It is your house; ensure you visit it every day during construction if you can.
An Australian innovation is the development of a chemically impregnated membrane that is only applied by accredited technicians during the course of construction. It goes under the whole slab and foundation areas in tune with the design of the building and doubles as an approved moisture membrane. Its big advantage is its longevity , and that it is installed by accredited technicians trained by the companies that offer the warranty. The data indicate protection with a useful residue of more than 50 years.
You can, by design, significantly reduce the likelihood of termite attack, however if, like most of us the house is up and you’re living in it, this chapter is only relevant if you decide to build your next home.