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RESEARCH UPDATE

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:

  1. Construct the primary building elements out of material that is not subject to termite attack, or
  2. 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, Professo?nash=1" 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

  1. University of Queensland Entomology Department 2002
    www.uq.edu.au/entomology/entonet/outlines/html.2/et2010/2010.term.html
  2. Archicentre News Release, Australian Termites $780 million smorgasbord
    www.archicentre.com.au/media/archinews18012003.htm 2003
  3. Standards Australia, AS 3660.1-1995 Protections of buildings from subterranean termites, Part 1: New Buildings
  4. Office of Fair Trading, FT030 Protect your house from Termites, NSW Consumer Protection Agency 2003
  5. CSIRO Forestry and Forest Products, CSIRO FFP Technical Report No 137. Termite Survey and Hazard Mapping
  6. Tyrells Property Inspections, Incidence of timber pest damage to steel framed residential buildings. 2000
  7. Jeary, A.P. Study of the Attack Rates by Termites and Costs of Associated Damage on Domestic Housing in New South Wales  2003
  8. 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.
  9. Australian Building Controls Board, Building Code of Australia, Volume 2. Class 1 and Class 10 Buildings - Housing Provisions.