structural pests

Estimates of the annual cost of termite damage to houses around Australia vary between $80 million [1] and $780 million [2].  The Building Code of Australia [9] gives the following options where the building is considered to be in an area susceptible to termite attack:

• Construct the primary building elements out of material that is not subject to termite attack, or
• Install a termite barrier in accordance with AS3660.1 [3]

A primary building element is defined as a member of the building designed specifically to take part of the building loads and includes roof, ceiling, wall, floor, stairway or ramp and wall framing members including bracing members.  The Queensland amendment extends this to cover doorjambs, window frames and reveals, architraves and skirtings.  Whilst AS 3660.1 uses the term “barrier”, it is also states:

“These barriers impede and discourage termite entry into buildings.  Termites can build around barriers but they can then be detected more readily during routine inspections.”

Termite management systems typically rely on termiticide chemicals sprayed on to the ground, or a physical mesh or termiticide-treated plastic barrier placed, before the concrete floor slab is poured.  Alternatively, the concrete slab itself can be used as a barrier, supplemented by chemical or physical treatments at penetrations and around the perimeter.  For elevated or suspended floor construction, continuous ant capping on perimeter walls and over piers is used.  The technical principle behind all of these approaches is the same: force the termite gallery construction crew to reveal its presence beyond the range of the concrete slab or metal-capped pier.  They do not stop the termites and hence they cannot be guaranteed to protect the house structure, fittings and contents.

The “barriers” can also fail due to poor workmanship during construction and lack of adequate maintenance.  Also some “barriers” can easily be breached due to inadvertent owner action such as building a garden bed adjacent to the house, where the mulch can be placed, so that the barriers can be breached unobserved.  The Department of Fair Trading in NSW stipulates that the builder must provide “whole of house” protection [4].  This is achieved by providing a termite “barrier” or deflector in accordance with AS3660.1.  As is being regularly highlighted by the current affairs programs on TV, this approach is failing.  The term “whole of house” protection is misleading and gives homeowners a false sense of security.

In 1999/2000, Australia’s CSIRO carried out a Termite Hazard Mapping project, looking at the incidence of termite attack throughout Australia [5].  From this study, a “hazard map” was constructed based on the percentage of homes attacked in various places, as reported by homeowners.  This map enables a prediction of the probability of termite attack in any given area.  The CSIRO study was broad and included a large statistical sample, but used as its basic indicator the percentage of homes attacked in a given area.  This percentage was then equated with “hazard”, without comment as to the cause, such as whether the termites were more aggressive, the homes differently constructed or the owners more vigilant in one place compared with another.

The CSIRO study did not attempt to examine the extent or cost of termite damage to individual properties.  No previous studies have attempted this, and consequently there has been a lack of information on the cost of termite damage, and more particularly on the differences if any between different forms and materials of construction.  The long-held belief in the steel framed housing industry, that steel-framed construction presented negligible termite risk, has frequently been ignored because it has never been proven through quantitative research.  Expert opinions, such as those provided by Tyrrells Property Inspections [6] based on a limited number of property inspection records on steel-framed homes, suggested a low or negligible risk but the volume of data needed to support this scientifically was simply not available.  Therefore NASH commissioned Foundation Professor and Head of Research, Professor Alan Jeary, Department of Construction, Property and Planning, University of Western Sydney to undertake an independent research study that would address the questions of attack rates and damage costs [7].  Given available industry knowledge of the suburban areas of Sydney containing similar examples of housing with both steel and timber frames, Professor Jeary designed a suitable homeowner survey and sampled approximately 900 homes in the period from June to September 2002.  The areas surveyed were in western, southern, northern and inner-western Sydney, avoiding housing in high termite risk areas close to bushland.  The survey collected information on house type, age, occupant demographics, building details, termite history and repair costs, general comments and observations.

A total of 263 useable responses were received – some 29% of the forms issued – representing homes in an age range from 2 to 40 years and averaging about 15 years.  Timber framed homes numbered 144 with 119 being steel framed.  Homes in the returned sample had values ranging from about $200k to $800k.  The study showed that whilst one in eight of the timber framed homes had suffered termite damage, not a single one of the steel framed properties was similarly affected.  Of those timber framed homes damaged, the average repair cost was just over $2300.  The conclusion from this study is that whilst pre-1995 termite management systems clearly haven’t done the job many builders and consumers expected of them, those homes constructed with termite resistant steel frames have remained free of termite damage.  Furthermore, since post-1995 termite systems remain essentially unproven in the field, we do not yet know the extent of protection afforded by these systems.  Growing industry and public concerns about the effectiveness of termite management systems [8] led to a Queensland variation to the BCA [9] in 2001.

Ken Watson   (Extract from presentation to Australian Forest Products Conference November 2003)

References

University of Queensland Entomology Department 2002 www.uq.edu.au/entomology/entonet/outlines/html.2/et2010/2010.term.html

Archicentre News Release, Australian Termites $780 million smorgasbord  www.archicentre.com.au/media/archinews18012003.htm 2003

Standards Australia, AS 3660.1-1995 Protections of buildings from subterranean termites, Part 1: New Buildings

Office of Fair Trading, FT030 Protect your house from Termites, NSW Consumer Protection Agency 2003

CSIRO Forestry and Forest Products, CSIRO FFP Technical Report No 137. Termite Survey and Hazard Mapping

Tyrells Property Inspections, Incidence of timber pest damage to steel framed residential buildings. 2000

Jeary, A.P. Study of the Attack Rates by Termites and Costs of Associated Damage on Domestic Housing in New South Wales  2003

Building News Flash 073 Proposed amendments to the BCA Housing Provisions – Termite Risk Management. Queensland Department of Communication and Information, Local Government, Planning and Sport.  2000.

Australian Building Controls Board, Building Code of Australia, Volume 2. Class 1 and Class 10 Buildings – Housing Provisions.

Termites are native Australian insects which live in the ground and feed on cellulose-based materials, including some we use for building homes, returning this organic material to the soil.

When people lived in trees and caves, termites were less of a problem!  The trouble started when we began to build homes in holes dug in the ground, using wood and similar materials.

Termites tend to be most active in warmer and wetter climates, the most destructive place being Darwin and the least, Tasmania.

Estimates of the damage termites cause to Australian homes range upwards from $100 million per year.  Some estimates of the total economic cost of termite management are as high as $750 million pa.

Once building warranties run out, almost all of the damage cost is borne by homeowners.  In any case, building warranty insurance will usually only cover termite damage if the builder has been proven negligent.

Some limited insurance plans are available, but they are usually tied to regular – and sometimes expensive – periodic inspections.

Even if you rely on inspections, be aware of their limitations.  Not all inspection specialists have the necessary skill and experience to detect current and past infestations.  Some infestations may elude even the most experienced inspector.

The problem is growing in high-population areas because of the way we build homes – and the physical and chemical methods we use to keep termites out – have changed over the past few decades.

At least four basic factors affect the termite damage risk to your home – and your pocket:

• where your home is located,
• how its foundations are constructed,what concealed structural materials are used, and
• how vigilant you are in inspecting and maintaining your home.

After you’ve built your home, it is usually too late to change your mind about the termite management system which protects your investment.

Builders can and should be a major source of advice – but make sure you ask the right questions about system effectiveness, lifetime cost and warranty protection.

Home building is subject to many rules and regulations including some which deal with management of termites.

The national code is called the National Construction Code (NCC).  It is published by the Australian Building Codes Board (ABCB).  Its members include representatives of all state governments, building research experts and industry representatives.

The NCC stipulates that where a home is subject to termite attack, as determined by the Building Authority, it must be constructed with:

• A termite management system complying with AS3660, or
• All its primary building elements made from termite-resistant materials.

Each state has agreed to apply the NCC by legislation, but some of the NCC provisions differ between states to suit specific local conditions or technical opinion – these are called “state variations”.

For example, the definition of “structural member” in Queensland includes some secondary building components.

Each state can also change the way it applies the NCC provisions, or impose its own additional requirements.

Just because there are rules doesn’t mean you can’t ask questions and get satisfactory answers and assurances.  It’s your money, so don’t spend more to get less!

The type of home you are building or extending affects the termite risk and the optimum termite management system.

What the rules state varies from state to state.

You may vary the design of the home to reduce the risk of termite damage (not “infestation”).

Some people and publications confuse “infestation” and “damage” but they are not the same thing.  An infestation may be quite real but quite harmless if detected before expensive damage to critical components results.

A harmless infestation can be valuable as an “indicator” of termite activity enabling nest treatment before expensive damage occurs.  Damage results from prolonged and undetected attack to inaccessible vital structural components.

How you protect different components of the building depends on:

• How important they are,
• Whether or not you can see and access them, and
• How expensive they are to replace.

There are two fundamental strategies:  seal them out and starve them out.  Building experts differ as to which method represents the best value for the homeowner.

It’s important to make termite activity visible as early as possible and to inspect and maintain your home regularly.  Do not let apathy prevent the early detection of termite activity.

The initial cost of a system is one thing but some systems require expensive re-treatment.  It’s up to the builder to recommend and install a termite management system, and up to you to maintain it at your cost.

As a homeowner, you need to know the lifetime cost of the system you are getting so you can determine whether it’s the most cost-effective solution.

The problem with sealing them out is that you can’t, absolutely.  Somewhere, somehow, they will get in – to your home or one just like it.

With sealing them out you are aiming to set up obstacles to termite entry – to kill, deter or divert them or to make their activity visible and treatable.

A wide range of alternatives is available but in practice not all will suit your home’s design and your builder may not offer all of them.

Chemical barrier treatments can be applied underneath or around a concrete slab, but allowable chemicals are now limited to products which have no proven long-term effectiveness.

Previously approved chemicals were highly toxic to both termites and humans and that led to lower than recommended dosage rates which still worked.  When this happens with newer chemicals, ineffective protection can result.

Some chemical systems include a reticulation system – a network of pipes under or around the slab through which the chemical protection can be periodically “topped up”.

Physical barriers usually use the concrete slab as the primary barrier, with mechanical barriers such as stainless steel mesh (eg Termimesh) or graded stone (eg Granitgard) around the perimeter.

All proprietary systems must be carefully installed by experienced operators.  They must supply documentation on what has been installed, where it has been placed and how it should be maintained.

Regular inspection for termite activity is good practice, but it is critical with barrier systems because the consequences of failure could be severe!

If the installed system does let termites through, your builder may in some circumstances be liable for repairs under a statutory warranty.  The length and terms of these warranties vary from state to state.

Extensions (at ground level) present particular challenges for physical and chemical barrier systems.  It may be difficult to determine what form of barrier is in place around the existing foundation and how best to integrate it with the new system while protecting the barrier system in the original construction.

The BCA allows another method of termite management, often called “termite resistant construction”.  It involves making sure that the main structure of the house is built entirely of termite-resistant  materials.

Termite resistant construction acknowledges that termites may be present and may attack a structure, but limits its consequences to easily-detected and easily-replaced non-structural components.

The most commonly used Termite resistant materials are bricks, steel, treated timbers, naturally-resistant timbers and concrete.

Queensland has widened the definition of “structural” to include secondary materials.

Termite resistant construction does not replace the need for inspections and good maintenance.  It reduces the level of skill required to detect a covert infestation and the consequences of non-detection.

The likely cost – over the life of the home – of replacement of secondary materials has to be compared with the cost of initial and follow-up barrier treatments, plus the cost of more regular and more expert inspection of barriers.  You the consumer will pay, so make sure you know exactly what you are getting.

When termite-resistant construction is used, further extensions using the same method present no particular difficulty.

Although the finished home is your domain, building it is the builder’s territory.  Builders may get defensive if their preferred and familiar methods are challenged without reason.

If this happens, remember that it’s your money and you want to make sure it’s spent wisely, now and on essential maintenance over the long life of the home.

You will be living with construction decisions long after the builder is physically, legally and financially out of the picture.

The basic questions:

• how much will the termite management system cost now?
• how long will it last?
• how should it be maintained?
• how will I know if it isn’t working?
• where will I stand if termites do get in and cause damage?

Ask your builder to propose several alternative termite management systems for your project.  Make sure that at least one option includes termite resistant materials.

Ask your builder to provide written evidence that each system offered is appropriate for the locality, site and type of building.  Ask your builder to itemise and explain the precautions, inspections, exclusions and any retreatment requirements.

Finally, ask your builder to calculate the lifetime cost of each termite management system offered, or to extend a lifetime warranty on the structural elements.