Termites cannot chew through sound concrete, but they can get through and around a slab. The Queensland Building and Construction Commission's guide to termite management systems says termites get inside buildings through wall cavities, cracks in mortar or concrete slabs, and gaps beside service entry points. A slab is a barrier, not a guarantee.
Why does a concrete slab count as a termite barrier?
The QBCC guide says a concrete slab on the ground can itself form a termite barrier, as long as it is built to the Australian Standards for residential slabs (AS 2870) and concrete structures (AS 3600). Building to those standards greatly reduces the chance of major cracking, and the termite standard, AS 3660.1, accepts the slab as part of the protection.
The barrier works because of how subterranean termites live. They need a link to the soil and they dry out in open air. CSIRO's Managing Termites guide explains that they build shelter tubes of mud to cross concrete, brickwork and durable timber, and usually forage within 30 m of the nest, sometimes 100 m or more. A slab does not stop the search for timber. It forces termites to find a gap or build a tube over the edge.
Where do termites get through or around a slab?
The weak points are the places where the concrete is not one solid, unbroken piece:
- Cracks through the full depth of the slab. A surface mark matters less than a crack that runs right through.
- Pipe and drain penetrations. Every plumbing pipe that passes through the slab leaves a joint. CSIRO lists rigid PVC or metal collars and fine stainless steel mesh as the physical barriers used around them.
- Construction joints. Where two pours meet, or a newer slab sits against an older one, there is a seam the soil can reach.
- The slab edge. CSIRO calls the face of the bottom wall plate fixed on the slab a prime access point, and notes that sprays applied to framing will usually not reach it.
- Wall cavities. In brick veneer and cavity brick, termites can travel up inside the wall where nobody sees them.
Menai has been developed since the early 1980s, and most of its homes are four-bedroom houses with double garages. A Menai owner who notices a long crack across the garage floor, with cartons and offcuts of timber stacked against the wall above it, should book a termite inspection in Menai so the crack and the stored timber are both checked.
Why does a covered slab edge matter so much?
The QBCC guide says most infestations happen at the perimeter of the building. One accepted way to manage that is to leave the slab edge exposed, with a 75 mm inspection zone shown in the guide's diagram. The guide is frank that an exposed edge will not stop termites. It brings them into the open, where their mud tubes can be seen and dealt with.
That only works while the edge stays visible. Paving laid flush with the slab, built up garden beds, timber decks and paths poured against the wall all hide it.
LJ Hooker developed Sylvania Waters in the 1960s, with much of the land reclaimed from the bay to give homes water frontages. A Sylvania Waters waterfront home where pavers run from the back wall to the pool and the water's edge, with no slab edge showing anywhere, should get a termite inspection in Sylvania Waters that checks every point where the paving meets the house.
Do extensions and renovations open new gaps?
Often. CSIRO warns that renovations and extensions must not compromise the existing termite barriers, and gives a common example. When a new concrete slab is poured against an old one, the gap between them needs sealing or protecting with a proper termite management system. New plumbing has the same problem, since every fresh pipe through the floor is a fresh penetration.
Taylor Woodrow built what is described as the country's first project home subdivision in north Woolooware, including the red brick houses of Taywood Street. A Woolooware family that added a rear living room on its own slab behind one of those older brick homes should arrange termite inspection and treatment in Woolooware with the join between the two floors on the list.
Attached structures can bridge a barrier too. The QBCC guide names carports, pergolas and fences fixed to the house without protection as common ways termites get past a system. Gymea saw most of its growth after World War II, so many of its houses are now decades old. A Gymea household with a timber pergola bolted to the back wall above a newer concrete patio should book a fast termite inspection in Gymea so the posts, the patio and the wall behind them are checked together.
Can you see termites coming through a slab?
Usually not. Termites that come up through a crack or beside a pipe can go straight into the wall frame without ever showing outside. CSIRO says most termite attacks start from the soil, and lists what inspectors look for: shelter tubes over slab edges, timber joints packed with soil, and damage to skirting boards, door frames, window frames and wardrobes.
If you do find a mud tube on the slab edge or a hollow skirting board, leave it as it is. Breaking it open or spraying it can push the termites deeper into the house and make the colony harder to track. The QBCC guide recommends inspections at least every 12 months, or more often in high risk areas, whatever the system under the house.
Before you book
Note these details so the technician knows where to look first:
- roughly when the house was built, and whether it sits fully on a slab or partly on stumps
- any extensions, and whether their floors were poured against the original slab
- cracks you have seen in the garage floor, tiled floors or outside paths
- where paving, garden beds, decks or patios meet the outside walls
- any plumbing or bathroom work that has cut new holes through the floor
Send those details when you contact our team for residential pest control in the Sutherland Shire: call Sutherland Shire Pest Control Pro on 02 8360 3033 or email [email protected].