Under the slab and around the edge

Termite barriers and new homes in Queensland

A new house built where subterranean termites are a known risk, with main structural parts that termites could attack, needs a termite management system under the building code, and Queensland’s variation says that system must have a design life of at least 50 years unless it can be readily topped up or replaced. At a minimum, QBCC says, the code requires protection for the roof and floor framing, door jambs, window frames and reveals, and architraves and skirting.

General information, not building advice. The official places to check are your building certifier, QBCC and the building code’s Queensland variations, listed at the foot of this page.

What Queensland adds to the national rule

The building code is national, but Queensland varies its termite part. The variations sit in the code itself and in QBCC’s booklet for builders and homeowners.

Queensland’s variations to the termite part of the building code’s housing provisions, as the code and QBCC set them out.
Topic	What applies in Queensland
Design life	For a non-temporary house, the system must have a design life of at least 50 years, unless it is easily and readily accessible for replenishment or replacement and can be replenished or replaced.
Hand-sprayed chemicals	For a house, chemicals cannot be hand-sprayed unless it can be proven they will last at least 50 years; otherwise, where chemicals are relied on below a concrete slab, a reticulation system may be needed so they can be topped up.
Chemicals around the edge	Trenches are dug, treated and backfilled with treated material, then covered by a concrete strip at least 50 mm thick and 300 mm wide, measured from the external wall.
What counts as structure	In QBCC’s words, the definition of “Primary Building Element” “is extended to include door jambs, window frames and reveals, and architraves and skirting, in addition to structural members.”
Access	The requirements take into account access for installing, maintaining and inspecting the system. QBCC’s example: hand-sprayed chemical perimeter barriers will not suit zero lot line housing.

QBCC also notes that termites are particularly aggressive in North Queensland, and that building in the north calls for a higher standard of termite protection.

The systems a builder can use

A termite management system is meant to cut the risk of termites reaching the main parts of a building by a hidden route. Installing a barrier will not stop termite activity on the site.

The options on QBCC’s homeowner page, with detail from its booklet. Combinations of systems are common.
System	How it works	What it asks of the owner
Concrete slab	The slab is part of the system, with another approved method protecting anything that passes through it, such as waste pipes.	Keep the exposed slab edge exposed: it brings termites into the open where they can be noticed.
Chemical	Approved chemicals under the slab and around the outside of the finished building, with a 300 mm concrete protection strip and a reticulation system to top up the chemical.	Meet the maintenance on the notice, for example yearly top-ups for chemical barriers.
Graded stone	Granite particles under the slab and around the perimeter, too hard to eat and too small for termites to move between.	Don’t bridge or breach it with garden beds, paths or attached structures.
Stainless steel mesh	Full or partial mesh under the slab and around the perimeter, or around single penetrations.	The same: keep the perimeter clear and inspected.
Termite-resistant materials	Treated timber, masonry, steel, concrete or fibre-reinforced cement, or naturally resistant timber.	Where they protect the main parts of the building, extra barriers may not be needed.

Generally, physical systems are designed to last the lifetime of the building with proper maintenance, while chemical systems have a limited life and need ongoing treatment. QBCC suggests weighing how much a system costs, how durable it is and how much maintenance it needs, and comparing warranties too; it warns that some installers may not honour their warranties where a combination of systems is used.

From contract to keys

Before you sign
Talk with your builder about managing termites while building and while maintaining the home. If you want a higher level of termite management, put it in the contract. Your builder may ask you to sign a form to confirm you have discussed the system you chose. QBCC recommends that acknowledgement notice be signed before the building contract.
The building application
The termite method must be shown on the drawings and specifications that go with the building application, and the certifier or approving authority decides which systems are acceptable. A performance solution should be discussed with the certifier before work starts, and no later than the building approval stage.
During construction
A QBCC licence is required to install termite management systems in new building work, and the certifier may ask the licensed installer to certify the installation. Other trades must take care too: concreters with slabs that abut the house, landscapers with paths and gardens, plumbers with pipe connections and electricians with conduits.
At handover
The builder should give the owner information on the system installed and the owner’s ongoing maintenance responsibilities, and the owner may have to declare to the local council, on its approved form, that they know which system was used. The durable notice goes up, usually in the meter box.
Living in it
Properly installed and maintained systems impede and discourage hidden entry, but they do not always prevent termites coming in the open, so they do not prevent attack on their own. That is what the yearly inspection is for.

Adding to the house later

Footpaths, garden beds, patios, pergolas, landscaping and new turf can all make a termite system less effective. The booklet adds detail an owner can act on:

A water tank installed against a perimeter wall may breach the visual inspection zone, let termites in unseen, and void warranty and insurance entitlements.
Freestanding structures should be built with an inspection zone of at least 25 mm between them and the house.
For a pergola, 75 mm is recommended between the finished ground or paving and the bottom of the timber posts.
A concrete path or driveway against the house may need a chemical reticulation system installed in the ground before the concrete goes down.

Buying a house built by someone else? The booklet puts the onus on the buyer to learn the system’s ongoing maintenance requirements, and the notice in the meter box is where that starts.