Preventing termite damage to buildings - safely and cheaply
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CTA. 1993. Preventing termite damage to buildings - safely and cheaply. Spore 46. CTA, Wageningen, The Netherlands.
Permanent link to this item: http://hdl.handle.net/10568/49174
In the tropics, termites are major pests of buildings such as offices and stores. Buildings of traditional construction may have to be replaced every 3-9 years; grain stores may need replacing annually. Entire villages have had to be relocated...
In the tropics, termites are major pests of buildings such as offices and stores. Buildings of traditional construction may have to be replaced every 3-9 years; grain stores may need replacing annually. Entire villages have had to be relocated because of termite infestation. Even modern concrete and brick buildings are not immune, since termite damage to door and window frames and wooden rafters can require costly repairs. In the past, highly toxic compounds such as copper aceto-arsenite (Paris green) or sodium arsenite were used to protect buildings against termites. They were replaced in the 1940s by organochlorine insecticides such as aldrin, dieldrin and chlordane. Concern over environmental damage caused by these insecticides led to their being banned or withdrawn from use in many countries. They were replaced by insecticides such as chlorpyrifos, oftanol, permethrin and cypermethrin. However, these materials are too costly for widespread use in many ACP countries where low cost, locally available solutions are needed. Most termite damage to buildings is caused by subterranean termites which live under, or near, buildings which they enter through cracks or by constructing soil runways over the footings and lower wall. From there, they move throughout the building either within the walls, or under soil runways on walls. The most effective method of control is to create a barrier between the building and the soil. This is most easily accomplished during construction and is more readily achieved in concrete and brick buildings than in traditional structures. Whatever the type of building, however, all potentially termite-attracting wood debris, including tree stumps and roots, should be removed from the site before construction begins. A concrete base provides an effective barrier to termites entering through the floor of a structure. It should be cast as a single slab on ground which has been well compacted to avoid subsidence and cracking of the base. Holes around services (pipes and cables) which pass through the slab should be sealed with a pitch-based sealing compound. Termites then need to construct soil tubes on the outside if they are to gain access to the building. If the base of the wall is kept clear of plants and debris and painted white, termite runways will be easily seen. They can be cleaned off to prevent termites becoming established inside the building. This treatment can tee very effective if carried out regularly. Termite shields fitted on top of the foundations, sleeper walls or piers also prevent termite access. The most effective shields consists of a continuous strip of copper, aluminium or galvanised iron around the building beneath the entire thickness of the wall and extending out from the building for 50mm then bent downwards at 45\B0 for 50mm (Fig la). All joints should be double locked and brazed or soldered. A simpler shield consists of a cement sill around the building, preferably with a groove cut into the underside (Fig 1b). Shields should be at least 180mm above the ground and should be inspected regularly for damage. Buildings of traditional construction are more difficult to protect. Many have a framework of wooden poles driven into the ground, which is then covered in mud or clay. Termites tunnel through the wood, wee ken the walls and destroy the structure. Walls made solely of mud may not attract termites, but the addition of straw to mud can encourage termites to tunnel into walls. Termites also tunnel through walls or construct soil tubes over them to attack the rafters and thatch. Wherever possible, termite-resistant wood should be used in construction. Several locally available materials are said to protect wood against termites. These include wood ash placed in post holes. Poles can also be treated by burning or charring the outer wood of the pole or painting it with used engine oil or creosote. Engine oil mixed into the soil along the base of the walls may also protect them. Some plant extracts (e.g. sap of Calotropis spp.) can protect timber for several months. Traditional grain and food stores may also be attacked. Some stores are more susceptible than others. Stores are built on top of 2m high slabs of rock in India to protect them against termites. In Zimbabwe, a base of resistant timber pro sects the store, while in Ethiopia the termite susceptible stilts below the stores are replaced annually. Oversized termite caps (Fig 2) on the legs of stores also protect the contents against rats and mice. We know that termite damage to traditional and modern buildings can be reduced or controlled without the use of in ported pesticides; further research would help to test and improve these alternative methods of control. Further work is being undertaken by the Natural Resources Institute (NRI). For information about finis work contact: Mr J Logan NRI Central Avenue Chatham Maritime Kent ME4 4TB UK