L.J. Cookson1 and A.C. Trajstman2
1CSIRO Forestry and Forest Products, Private Bag 10, Clayton South, Victoria 3169
2CSIRO Mathematical and Information Sciences, Private Bag 10, Clayton South, Victoria 3169
June 2002
A joint investment with the Forest and Wood Products Research and Development Corporation (FWPRDC)
The information contained in this report is copyright, and cannot be copied without the written permission of CSIRO or the FWPRDC.
Interviews were conducted Australia wide during 1996-8 to determine the influence of location and house construction type on termite activity. Information on 5122 dwellings was obtained, with the majority coming from a 'Termite Tally' survey conducted by the Double Helix science club.
- The mean house age was 30 years, and the mean occupancy duration was 11 years. Lowest mean house age occurred in Darwin (result of Cyclone Tracey).
- Timber was the most common framing material in Victoria, Tasmania, Queensland, NSW and the ACT. Masonry framing materials predominate in WA, SA and NT. Steel alone accounted for only 5% of house framing, with the highest proportion in the NT.
- Timber is the most common flooring material in Tasmania, Victoria, NSW and the ACT. Concrete floors are most common in the NT, Queensland, SA and WA. Combinations of floor type (timber and concrete) are more common than combinations of frame type.
- The dominant factor affecting termite incidence inside houses was house age.
- The occurrence of termites inside a house was not significantly affected by house construction type (timber, masonry, concrete, steel or their combinations).
- Termite eradication was most successful by chemical treatment of soil or wood. Least success was obtained by ignoring the problem, followed by simply disturbing the affected area.
- Termites inside houses were most often found in walls, flooring, house stumps, architrave and skirting boards, joists, bearers and window frames. Termites were less common in roofing timbers.
- Termites outside were most often found in wood piles/branches, live and dead trees, fencing, sleepers, dead tree stumps, and the garden shed.
- Termite presence was most often noticed by the damage caused to timber, followed by mud tube construction.
- A verification survey of 44 Double Helix students revealed that houses were chosen at random. The randomisation involved choosing family friends at random to participate, or randomly choosing family friends in their neighbourhood. However, one student admitted that old timber houses were selected for part of his sample in preference to non-timber homes.
- The ability to distinguish termite activity was high, although obviously less than for trained specialists. Of 109 'termite' samples sent to CSIRO for identification, 106 were in fact termites.
- The relative information gathered was considered suitable for the initiation of an interim Australian termite hazard map. An agro-ecological map provided by The Agriculture Working Group on Ecologically Sustainable Development was used as the framework upon which the termite incidence data was applied. Maps illustrating termite incidence inside and outside were produced.
- An interim termite hazard map for Australia was constructed based mainly upon the termite incidence outside data. This map represents the termite pressure that might threaten buildings.
- However, buildings were at less risk of attack than suggested by the interim hazard map, due to existing building practices and control measures.
- The interim hazard map suggests that the most important factor determining termite distribution is temperature, followed secondly by rainfall. Vegetation and soil type appear to play a more minor role within the dominant effects of temperature and moisture.
An important part of determining the durability of timber is to understand the hazard it will face in service. Before the Forest and Wood Product Research and Development Corporation funded project 'Design for Durability', there was no uniform measure of termite hazard across the country. Some localised termite surveys had been conducted. For example, termite incidence in Melbourne (Howick, 1966), Perth (Postle and Abbott, 1991), and Sydney (Reynolds and Eldridge, 1973). Also, maps of each termite species were available (Watson and Abbey, 1993), and while these provide guidance they indicate termite species distribution rather than hazard or termite pressure. Hazard is a relative measure of the conditions that threaten timber, while risk is the threat faced by a particular type of timber or timber construction that varies in resistance (Barnacle and Cookson, 1995). Therefore, hazard is most easily determined using timbers of high risk (low durability), as they will be attacked in short enough time to provide a relative measure. This method of hazard determination could work for one termite species, but complications arise when the overall hazard from 'termites' is sought, because each species varies in its food preferences and even food orientation (e.g. preference for timber laying on the ground, or in-ground).
The aim of this contribution was to determine the hazard faced by buildings in Australia to wood-feeding termites. However, the distribution of house type across Australia is not uniform, so the influence of house age, construction type, and any termite management system adopted also needed to be determined. To obtain a random sample of houses, a 'Termite Tally' survey was instigated by Dr John French through CSIRO's Double Helix science club. This survey produced data for 4194 buildings, from 248 students. Data for a further 145 houses were obtained by a CSIRO telephone survey, targeting areas under-represented in the Double Helix data. An additional survey was conducted through an email survey to 'CSIRO All', resulting in 783 responses. Therefore, the total data set was 5122. A verification study of the Termite Tally survey was also undertaken to obtain an indication of the reliability of the data collected.
The purpose of this report is to provide a tabular summary of the results, and to describe the steps taken in the construction of the termite hazard map.
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