Nearly every slab on ground house on the northside has a strip of concrete showing between the bottom of the render and the ground. That strip is the slab edge, and it is the single most useful diagnostic surface on the property. A subterranean termite colony is coming from the soil, and it has to get from the soil into the timber without crossing open air, because open air dries it out and kills it. The slab edge is where we can see it trying.
Which means the rule is simple. If you can see the join between the wall and the slab, all the way around the house, a lead has to be built in the open where anybody can spot it. If you cannot see the join, the lead can be built inside a covered route and the first sign will be structural.
1. A garden bed built above the slab edge
This is the one we find most often, and the Cashmere house that changed how we work was exactly this. Somebody lands soil or mulch against the wall to tidy a bed up, and the level ends up above the slab edge. Two things happen at once. The termites get a covered bridge over the treated zone, and the soil holds water against the footing so the wall stays damp. Drop the level back so there is at least 75 millimetres of bare slab edge showing, and keep the mulch off the render. It costs an afternoon and a shovel, and it is the highest value thing a homeowner on the northside can do.
2. A weep hole rendered over
Weep holes drain the cavity and let it breathe. Rendering across them, or packing them with mortar during a renovation, turns a ventilated cavity into a wet one. They also matter as an entry point in their own right: a weep hole is a small hole into the wall, which is why we fit stainless weep hole screens on jobs where they are the obvious route. Walk the house and count them. If there is a long run of wall with none showing, they have been covered.
3. A path, patio or driveway poured across the join
New concrete poured hard up against an existing slab creates a cold joint that runs straight to the footing, and it buries the edge you were meant to be able to inspect. This is not a fault you can dig out with a shovel. It is why termite management on a house like this is usually drilled and injected through the hard surface rather than trenched: we drill the path on a spacing, inject the treatment down the joint and patch it. Worth knowing before you landscape, because telling us first means we treat one section rather than reinstate the whole barrier.
4. A tap, downpipe or air conditioner discharging at the footing
A dripping garden tap, a downpipe that empties beside the wall, or an air conditioner condensate line running onto the ground at the footing. All three keep one patch of soil permanently damp, and damp soil beside a footing is exactly what a foraging colony is looking for. On a thermal read this shows up before anything else does. Extending a condensate line two metres away from the house is a ten minute job with a length of hose.
5. Timber, boxes or a stack of anything against the wall
Firewood, offcuts, the pallet the pavers came on, a stack of cardboard beside the garage. Any of these gives a colony a food source in contact with the ground and a covered route up the wall, and all of them make that section of wall inaccessible on the day we inspect. Move it off the ground and away from the building, and the problem goes away with it.
What to do with what you find
- Walk the whole perimeter once, slowly, and look at the bottom 300 millimetres of wall. That is the whole exercise.
- Fix one, two, four and five yourself. They are soil, mortar, water and storage.
- Do not attempt to fix number three by chipping at concrete. Get it assessed.
- If you find mud tracks while you are down there, stop. Do not touch them, do not spray them and do not knock them off. A live lead is the fastest route to the nest and disturbing it scatters the colony.
- Book the annual inspection anyway. Every builder warranty and every termite management warranty depends on it, and a barrier is a line the colony has to cross rather than a wall.
A termite inspection here runs $265 to $440 depending on the house, and it is reported to AS 4349.3 with photos of every finding and every conducive condition. If you fix the five above first, that report gets a lot shorter and a lot cheaper to act on.