Slab as a termite barrier, or full under slab?
A concrete slab can be part of the termite system. Whether that is enough depends on how the slab is jointed and how it will crack.
Written for builders, engineers and specifiers. It isn’t legal advice: your certifier makes the call on each project.
The short answer
- A slab built to AS 2870 or AS 3600 can act as a termite barrier across its area.
- The entry points still need a termite management system: service penetrations, construction joints and the slab edge.
- Saw cuts are made after the pour. They are not an entry point on the day, but the slab is designed to crack along them in the future.
- Protecting the penetrations, construction joints and perimeter only covers the openings that exist on the day of the pour.
- A full under slab barrier covers the whole footprint, so saw cuts and later cracks already have the termite barrier beneath them.
When the slab is the barrier
AS 3660.1 lets a slab on ground form part of the termite management system when it is designed and built to AS 2870 or AS 3600. The concrete does the work across its area, and a termite system is installed only at the entry points.
This is the most common approach, and on the right slab it is a sound one.
What still has to be treated
- Every service penetration.
- Every vertical construction joint, whether or not the reinforcement runs through it.
- The perimeter, unless the slab edge is left exposed for inspection.
Why saw cuts matter
A saw cut only goes part of the way through the slab. It is there so the slab cracks along that line and not somewhere else, and the crack runs the rest of the way through beneath the saw cut. Engineers design them so the slab can move without damaging the structure.
When the termite system goes in, a saw cut doesn’t exist yet, so there is nothing to treat. Once the slab has cracked along it, it is a joint through the full depth, and the only place a barrier can sit is underneath. On a large slab that can be hundreds of metres of future joints, and every one is a termite entry point.
A full under slab barrier covers them, because it is already beneath the slab wherever the saw runs.
What the builder signs for
When the slab is part of the termite system, the installation certificate needs the builder’s or concreter’s certification that the slab complies with AS 2870 or AS 3600.
Collars on the penetrations and physical barrier strips at the construction joints and perimeter protect the openings that exist on the day of the pour. A crack that forms later, away from those, has no termite barrier under it.
What full under slab changes
- The barrier covers the whole footprint. Saw cuts and later cracks already have the termite barrier beneath them.
- Saw cut positions don’t matter. The saw can run wherever the engineer wants it.
- It replaces the membrane. JH Termite Barrier also serves as the vapour barrier, so it takes the place of the plastic and isn’t an extra layer.
- One system across the slab. The sheet repels and kills termites over the whole area, not only at the joints.
Which suits your project
Penetrations, construction joints and perimeter usually suits
- Smaller slabs with few joints.
- Slabs with no saw cuts, or very few.
- A slab edge left exposed for inspection.
Full under slab usually suits
- Large slabs with saw cut grids.
- Reactive or moving ground.
- Many pours and construction joints.
- Buildings where the floor can’t be lifted later, such as healthcare, education and retail.
This is our advice from installing both, not a rule in the standard.
Is a concrete slab a termite barrier?
It can be part of one. AS 3660.1 accepts a slab on ground designed and built to AS 2870 or AS 3600, provided every penetration, construction joint and the slab edge is protected as well.
How are saw cut joints protected from termites?
A saw cut is made after the pour, so it can’t be treated on the day, and the slab then cracks along it. A full under slab barrier covers it because the barrier is already beneath the saw cut.
Do construction joints need protection if the steel runs through?
Yes. Vertical construction joints need a termite management system whether or not the reinforcement is continuous.
What happens if the slab cracks after construction?
Where only the penetrations, construction joints and perimeter are protected, a crack away from those has no termite barrier beneath it. A full under slab system already covers that area.
Does a full under slab barrier replace the vapour barrier?
JH Termite Barrier does. Its polyethylene outer layers act as the vapour barrier and damp proof course when it is laid as a full under slab system.
Can you price both options?
Yes. Send us the slab plan and joint layout and we’ll price the penetrations, construction joints and perimeter on their own, and full under slab, so you can compare them.
Sources
Standard and manufacturer sources used for this page. Rules change: confirm the current requirements with your certifier.
Not sure which way to go?
Send us the slab plan and joint layout and we’ll price both ways, so you can compare them.