are active in nearly every residential block, although not all damage timber.
Isolating the superstructure of the house (containing the
edible components) from the ground is the most important part of protecting it from
termite attack. This can be done in three ways:
- Make the building unattractive to termites;
- Use barriers and design features to prevent termites
invading the building;
- Ensure the building is easily accessible for termite
buildings unattractive to termites
Termites are especially attracted to timber that is damp
and infested with wood-decaying fungi. Proper site preparation, the use of timber
alternatives, termite resistant wood and timber preservatives, and prevention of dampness
will deter termites.
All tree stumps, roots, other wood and timber products (for example, cardboard and paper)
should be removed from the new house site or burnt before construction. Avoid the use of
wood in direct contact with the ground. Attach wooden posts to steel fittings concreted
into the ground with 50 to 100 mm between the wood and the ground. Seal the top of steel
fittings fabricated from hollow tubing with welded plate to prevent concealed termite
Keep stacks of timber or firewood well clear of existing
buildings. However, termites on firewood brought inside are unlikely to cause an
infestation as the queen will not be located in surface timber and workers isolated from
their nest will die. Avoid using timber in garden landscaping and retaining walls. Even
naturally resistant timber, such as jarrah, could become subject to attack under damp
conditions. Timber in gardens may encourage termite activity and increase the likelihood
of the establishment of new termite nests.
Steel trusses in roofs and steel door frames are practical alternatives to timber.
Use resistant timber where possible, especially in exposed positions or in contact with
Resistant timbers are wandoo, blackbutt, jam,
jarrah, western red cedar and kapur. Also resistant are the Australian native
cypress pines and Australian cedar.
Susceptible timbers include pine, karri, marri,
mountain ash, meranti and particle board. All sapwood, even of resistant species, is
No timber is totally resistant to attack.
Creosote can be an effective timber preservative, preventing termite attack and wood rot.
Protection depends upon the depth of penetration. Simply brushing creosote on wood
surfaces gives little protection. Multiple applications by brush are better, but
preferably soak the timber in creosote for at least 48 hours. All cutting and hole boring
should be completed before soaking. Round fence posts of seasoned softwood timber, with
sapwood present and the bark removed, can be successfully treated in a similar manner.
Stand posts 'top down' for at least one hour in 1 to 1.5 m
depth of creosote in a 200 L drum. Then, invert the posts and soak the butts (timber in
contact with the ground) for several days. The preservative readily enters sapwood. For
butts, the rate of absorption should be 160 g/L of sapwood. Tops require about one-third
Softwoods, such as pine, can be effectively treated with
salts of copper-chrome-arsenic (CCA). This gives the timber a greenish appearance and can
protect against fungi and termites for more than 20 years.
The heartwood of Australian hardwoods cannot be effectively
treated because it is dense and resists penetration by the preservative.
Ensure that storm water is shed away from buildings using paving sloped at an adequate
angle away from the foundations. Direct gutter outflow to storm water drains or soak wells
situated well away from the foundations. Avoid placing garden beds and associated
reticulation adjacent to the house foundations. Never construct raised garden beds
abutting the outside wall of the house. Internal gardens or conservatories can create
special problems and owners should consult the architect or builder about protecting these
Dampness around bathrooms and laundries in houses with
suspended floors causes special concern, since tile grout allows moisture to seep through.
Pre-formed fibreglass shower floors, which don't allow water seepage, can be used in some
circumstances. Water and sewerage pipes under buildings should be free of leaks.
Correctly fitted air vents provide adequate ventilation of
sub-floor spaces and keep timber dry. They also provide light, which termites find
termite access difficult
Building design and physical and chemical barriers are
effective ways of preventing termite attack.
Concrete slab-on-ground construction is the most common type of construction, but is
susceptible to termite entry. Concrete slabs, which retain moisture under them, attract
Standard building practices involve pouring the concrete in
two stages. The foundations are laid first and then the concrete slab is poured to overlap
the foundation. The joints between the foundations and slab can crack giving termites
access to the cavity walls (see Figure 2), roof and other timbers.
Covering the bottom one or two courses of the outer leaf
brick wall with soil is the most serious design flaw in standard constructions. This
provides termites direct concealed access to the cavity walls and from there to most
structural and cupboard timber in the house (see Figure 2).
The common practice of using thinner concrete,
or no concrete at all, under the bath markedly increases the risk of termite attack in the
The concrete slab can act as a physical barrier (see AS
3660.1-1995) itself, if it is constructed correctly to a minimum specification which
satisfies AS 2870.1. The use of vibrators for compaction is strongly recommended.
Pouring the foundations and slab in one operation
(monolithic slab) and bonding the two with steel reinforcements significantly protects the
cavity walls and is recommended (see Figure 3).
Make the outer edge of the concrete foundations clearly
visible. Ideally 75 mm of concrete should be clearly visible above the final finish level
of the soil (see Figure 3). This markedly increases the building's resistance to termites.
Exterior formwork is required to produce a 'finished' edge to the concrete which can then
be painted to make it less obvious.
Termites can enter a building through the cracks and along
air pockets formed around plumbing and electrical service pipes installed in the concrete.
Using a mechanical vibrator on the concrete in these areas can improve the resistance of
the structure. Penetrations through the slab (plumbing, electrical and other service
pipes) and any joints in the slab need to be protected by a suitable chemical or physical
barrier. Chemical barriers are required to be continuous under the entire sub-floor
Using adequate steel reinforcing and 'haunched' footings
under internal, load bearing walls can help stop the slab cracking. Allow at least seven
days curing time before heavy loads (for example, vehicles, brick stacks) are allowed onto
the surface and before construction starts.
Houses with suspended floors on steel or brick and concrete piers fitted with termite caps
or shields, with adequate clearance (400 mm minimum), ventilation and light are the most
termite resistant. Possible access points are steps, service pipes or the concrete
slab-on-fill construction, often used under wet areas such as laundries and bathrooms.
Steps should be separated from the house by at least 50 mm.
Design additions and renovations so that the superstructure of the building remains
isolated from termites. Modifications can significantly increase the vulnerability of the
building to termites.
Patios, pergolas, gate posts and steps can make a building more vulnerable to termites.
Free standing patios and pergolas should be separated from the house by 50 to 100 mm. If
they are attached to the house, pay attention to where they contact the ground. Avoid
using wooden posts in direct contact with the ground. Attach wooden posts to steel
fittings concreted into the ground with 50 to 100 mm between the wood and the ground. Seal
the ends of hollow steel fittings in all constructions with welded plate to prevent
termites entering the wood through the tubing. Ensure a 50 to 100 mm clearance between
gate posts fixed in the ground and the building. Alternatively, gate posts fixed to the
building should clear the ground by 50 to 100 mm.
Similar principles apply to the construction of sheds. Avoid embedding timber posts
directly into the ground. All timber should be clear of the ground by at least 50 mm.
Place termite caps or termite strip shielding between the building superstructure
and its foundations in constructions with suspended floors. Physical barriers are
constructed from metal with the edge angled downwards at 45 degrees. Correctly constructed
strip shielding can act both as a damp course and termite barrier.
Effective physical barriers need adequate site preparation.
Remove all timber and builder's rubble from the site. Construction of these barriers is
covered by Australian Standard 3660.1-1995.
Termite caps and strips do not provide complete protection
against termite attack. However, where an attack occurs, they force termites to build
their shelter tubes where they can be detected easily and treated. Thus, where physical
barriers are used, provide adequate access for regular inspections.
Stainless steel mesh (TermiMesh®) is approved
for use as a termite barrier. A layer of steel mesh, with holes too small for termites to
penetrate, provides a barrier against attack. Stainless steel mesh barriers are best
installed during the construction of the building, since fitting the mesh after
construction is difficult and not as effective.
There are two basic options for installing
stainless steel mesh to concrete raft constructions. The first involves a complete cover
(see Figure 4) under the entire floor with clamp fittings around any pipes that penetrate
the slab. This is the most expensive option ($4000 to $5000 per building) but provides the
most complete protection. Partial installation (see Figure 5), across cavity walls and
around the pipe penetrations only, reduces the cost substantially (about $1000, which is
comparable in cost to a complete chemical treatment) and gives protection against most
instances of termite penetration.
Installation of stainless steel mesh involves
only an initial cost, but competent annual inspections are required. Partial installation
requires an upgraded slab which conforms to Australian Standard 2870.1-1988: Residential
slabs and footings. Part 1: Construction.
Graded stone has been accredited as a physical barrier. A
base of compacted gravel of a specific size range is laid under the normal concrete pad.
The method works on the principle that the individual granite particles are too heavy for
individual termites to move and are too small to provide gaps large enough for the
termites to penetrate.
Graded stone can be installed as a complete barrier under
the concrete slab or as a partial barrier where it must be restrained so as to remain in
contact with the other surfaces which comprise the barrier. Refer to AS 3660.1-1995 for
installation requirements. When used as a partial installation, the concrete slab must
conform to specifications set out in AS 2870.1.
barriers for new buildings
Chemical barriers must be continuous under the whole of the structure to be
effective. Partial installation of chemical barriers is not sanctioned by AS 3660.1. All
foundations should be surrounded by, and be in contact with, an insecticide-treated layer
Form chemical barriers after completing all site works
levelling, excavation, filling and compaction; and after the installation of
ground-located electrical conduits and plumbing pipes. This is immediately before laying
the floors of buildings with suspended floors or immediately before placement of
waterproofing membranes for buildings with concrete floors. Table 1 shows the chemicals
registered for use as termite barriers and their application concentrations.
Table 1: Insecticides for soil treatment of buildings under
construction to protect against subterranean termites.
Concentration to use
1 g/L south of the Tropic of
Capricorn; 1.5 g/L north of the Tropic of Capricorn.
Biflex® Preconstruction Termiticide
10 g/L south of the Tropic of
Capricorn; 20 g/L north of the Tropic of Capricorn.
Dursban® Preconstruction Termiticide
in Australia; Check regulations in your country first
(**) Grams of insecticide (active ingredient) per litre of solution.
Apply the emulsions of the insecticides listed
in the table uniformly, at not less than 5 L/m2
for horizontal barriers. Vertical barriers in contact with foundations require 100L/m3 of soil and should be 150 mm wide against the wall to
Requirements for installing soil insecticide
barriers against subterranean termites, for buildings under construction, are given in AS
Prospective home builders should be aware that chemical
barriers will not last the life of the building. Re-treatment intervals of six to 10 years
are stated on the respective chemical labels. Re-treatments may not be required after this
period but annual inspections by a licensed pest control operator are recommended.
Re-installation of a chemical barrier underneath a concrete slab may require floor
coverings to be removed, holes drilled through the floor and chemical injected unless an
approved reticulation system was installed at the time of construction.
Site preparation can maximise the effectiveness of
insecticide barriers. Remove all stumps, tree roots, timber and other debris before
For slab-on-ground constructions, chemical barriers can be
installed only at the time of construction (except where under-slab reticulation systems
are used - see below).
Below-standard termiticide applications involving
understrength termiticide concentrations and reduced volumes of termiticide per unit area
have been reported. As a guide, in October 1995, the cost of a termiticide barrier
underneath a concrete slab (pre-construction) was about $5.25/m2,
including the perimeter. Consumers should be wary of quotes which differ much from this
Similarly, to apply 5 L/m2
of termiticide via low pressure spray is time consuming and could take more than one hour
per building site.
These costs can be substantially greater above the Tropic
of Capricorn where higher chemical rates are required.
Correct installation of a chemical termite barrier involves
at least two separate treatments. The major barrier is under the concrete slab as
described above. The final treatment is to the outer perimeter of the foundations after
all service connections have been completed and all backfill is in place. An initial
treatment to the foundations is also required where these are poured separate to the
All these treatments are part of the complete termite
barrier as described in AS 3660.1-1995 and should be included in the building contract.
Concrete garage floors are usually poured separately and
late into the construction of a house. Hence, they are often untreated and can weaken a
building's termite protection. Chemical barriers are required to be continuous under
concrete floors, including garages and carports.
If the garage is part of the house and is under the main
roof, this treatment is the responsibility of the builder and should be included in the
ALTIS® and Termguard® are
under-slab reticulation systems currently approved for use. They are installed
pre-construction, underneath the slab and waterproof membrane. A chemical barrier is
installed by injecting the insecticide under the slab at any convenient time between
pouring the slab and completion of the house.
If a reticulation system is installed, it must be charged
with chemical soon after the house is completed to satisfy building requirements.
The exposure of children to the termiticide barrier applied
around the outer perimeter of a building is not considered a significant health risk. This
is partly owing to the binding of the chemical to the soil and the evaporation of the
solvents and emulsifiers soon after application.
It is possible to dispense with this treatment if the outer
edge of the concrete slab is exposed 75 mm above the final finish level of the soil (see
barriers for existing buildings
Treat existing buildings with bifenthrin (Biflex®) or
chlorpyrifos (Chlorpyrifos PCO®, Deter® or Dursban®).
Higher rates (refer to the pesticide label) are required north of the Tropic of Capricorn
to control the giant termite, Mastotermes darwiniensis.
Where the sub-floor area cannot be reached, a trench
extending down to the top of the foundation and 150 mm wide around the outside of the
building is an option. Dig the trench in contact with the foundations and then backfill it
with treated soil using 100 L/m3 of
Another application method for external barriers is to pump
insecticide emulsion through a specially designed perforated pipe. The pipe is driven into
the ground around the perimeter of the building, close to the foundations, to a depth of
300 mm at frequent intervals so that insecticide from adjacent injections meet.
Do not plant large trees close to buildings, since tree
roots can broach insecticide barriers.