Termite management in a new home: what the code requires, and why it fails later

Subterranean termites don't come through the front door. They come up from the soil, through gaps you can't see, and they eat timber from the inside out. By the time the damage shows, a door frame, a skirting board or a roof timber may be hollow. Termites are active across most of Sydney, so a new house here has to be designed and built to manage them from the ground up.

The good news is that termite management in a new home is well understood and is largely settled before the slab is poured. The bad news is that the system can be defeated years later by ordinary things, like a new garden bed, a paved path or a deck, if nobody knows it's there. This article explains what the code requires, why it's written that way, and how to keep the system working.

What the code requires

For houses (Class 1) and associated structures like garages and sheds (Class 10), termite risk is covered by the National Construction Code (NCC) 2022 Housing Provisions, Part 3.4 Termite risk management. It applies where a building is in an area where subterranean termites are known to present a risk and its primary building elements are susceptible to attack. The code notes that termites are not considered a risk in Tasmania and are a lesser risk in parts of Victoria. Sydney is not one of those exceptions.

Part 3.4 is built around three clauses:

• 3.4.1 Requirements. Primary building elements that could be damaged by termites must be protected. Elements made from materials termites can't damage don't need a system. The code lists steel, aluminium and other metals, concrete, masonry, fibre-reinforced cement, and timber that is naturally termite resistant or preservative treated in line with AS 3660.1.
• 3.4.2 Termite management systems. Where a system is needed, it must comply with AS 3660.1, or have passed the tests in Section 5 of AS 3660.3. The code's table of acceptable systems sets out options by part of the building.
• 3.4.3 Durable notice. A permanent notice must be fixed to the building in a prominent location, such as the meter box. It must state the type of system used, the date of installation, the life expectancy of any chemical, and the installer's or manufacturer's recommendations for the scope and frequency of future inspections.

For a slab-on-ground house, the acceptable options are broadly:

• At the slab perimeter: slab edge exposure, sheet material, granular material, or a chemical barrier.
• At penetrations, control joints and under the slab: sheet material, granular material, or a chemical barrier.
• For attachments such as decks, steps, downpipes and pergolas: either a termite management system to the attachment itself, or an inspection zone between the attachment and the building.

In practice, the main approaches are:

• Physical barriers. Sheet materials, including stainless steel mesh and proprietary barrier sheets, and graded stone (granular) barriers that termites can't move through. Collars fitted around every pipe and conduit penetrating the slab are a key part of this.
• Chemical barriers. Treated soil zones, often with a reticulation system of pipes around the perimeter so the chemical can be topped up over the building's life.
• Termite-resistant materials. Preservative-treated framing (commonly H2 treated pine for above-ground framing in termite areas), steel framing, or naturally durable species. Resistant materials reduce what the barrier has to protect, but they don't replace inspections.

Why the code is written this way

Termites are a soil problem, so the defence starts in the soil. Subterranean termites live in the ground and travel to timber through soil, mud tubes and concealed gaps. The code puts the barrier where they come from: under and around the slab, at every penetration, and at every point where something touches the building.

Concrete doesn't stop them on its own. Termites can get through cracks, control joints and the gaps around service penetrations. That's why the code lists penetrations and joints separately from the slab perimeter. A barrier that protects the edge but leaves a gap around a plumbing pipe is not a barrier.

No barrier is a guarantee, so the system relies on inspection. Barriers are designed to stop concealed entry and force termites into the open, where a trained inspector can see their mud tubes. That's why slab edge exposure is an accepted option, why attachments need inspection zones, and why the durable notice must state how often the system should be inspected. The barrier and the inspection are one system. Either one alone is much weaker.

Future owners need to know what's there. A house outlives its builder's memory. The durable notice exists so that whoever owns the house in 15 years, and whoever inspects it, can find out what system was installed, when, and how it should be maintained.

The damage is hidden and expensive. Termites eat timber from inside, so damage is usually found late. Many home insurance policies exclude termite damage, so check your own policy wording rather than assuming you're covered. Either way, the cost of prevention is small next to the cost of repair.

Where termite management goes wrong

Most failures aren't in the product. They're in what happens before the pour and, more often, after handover.

• The slab edge gets covered. Where slab edge exposure is part of the system, the exposed edge has to stay exposed and visible. Paving laid up against it, garden beds built over it, soil built up by landscaping, or render carried down over it all give termites a hidden path past the barrier.
• Penetrations are missed. A pipe or conduit added late, or a collar not fitted or damaged during the pour, leaves a gap straight through the slab.
• Attachments bridge the barrier. A deck, step, retaining wall, pergola post or even stored timber against the wall can give termites a route that bypasses the system.
• Inspections stop. Many barrier warranties depend on regular inspections in line with the installer's recommendations. Skip them and you may lose both the early warning and the warranty.
• The durable notice is missing, or nobody reads it. Without it, a new owner or a renovator has no idea what system is in place or what not to disturb.
• Chemical life expires unnoticed. Chemical barriers have a stated life. If nobody tracks it, the barrier simply stops working.

Our companion posts cover inspections for existing homes and how renovations and landscaping can breach a barrier.

Questions to ask your builder

1. Which termite management system is proposed for the slab perimeter, penetrations and under-slab area, and does it comply with AS 3660.1?
2. Which framing material and treatment is being used, and to what hazard level?
3. Who installs the barrier, and is it inspected before the slab is poured?
4. How are penetrations and attachments such as decks and steps being treated?
5. Where will the durable notice be fixed, and what will it say?
6. What inspections does the installer recommend, and what do I need to do to keep the warranty?
7. If slab edge exposure is part of the system, which areas must stay exposed, and how will the landscaping plan respect that?

How we build it

• We settle the system at design stage. The barrier type, framing treatment and approach to attachments are chosen to suit the site, the slab design and the landscaping, not left to the week before the pour.
• We hold before the pour. Barrier installation, penetration collars and sheet laps are checked and photographed before the concrete goes in, alongside the reinforcement and vapour barrier. Once the slab is poured, none of this can be seen again. Our article on hold points and the handover record explains this method, and footings and slabs covers the rest of what we check at that stage.
• We coordinate the trades that can breach it. Plumbers, electricians and landscapers are briefed on the system, and late penetrations are treated, not ignored.
• We fix the durable notice and hand over the paperwork. The notice goes in the meter box, and the owner receives the installer's certificate, product details, warranty terms and inspection schedule.
• We tell you what not to do. At handover we point out the inspection zones and slab edges that must stay clear, so the system still works after the garden goes in.

Frame material is part of the picture too. Our article on timber frame construction myths covers how termite risk applies whatever the house is built from.

If you're planning a new home or an extension and want to talk through termite management, get in touch.

Sources

• NCC 2022 Housing Provisions, Part 3.4 Termite risk management, Australian Building Codes Board
• Termite management, WoodSolutions (forest and wood industry technical resource)
• AS 3660.1, Termite management — New building work, Standards Australia

This article is general information, not advice for your project. Termite management requirements depend on the site, the building and the products used, so confirm them with your builder, a licensed pest management technician and your certifier. Full website disclaimer