Non-poisonous timber protection
Practical Action
Disadvantage of chemical treatment
The chemical treatment of wood is designed to prevent wood-destroying organisms such as
insects and fungi from attacking and weakening the timber, or to prevent the further decay of
timber that is already affected. Usually this is achieved by using highly toxic insecticides and
fungicides, but
Fungicides and insecticides have to be sufficiently toxic to be effective. They cannot
differentiate between harmful and harmless organisms, which are both destroyed.
The chemicals affect animals and humans by skin contact, inhalation, or through
contaminated food, causing a variety of health problems ranging from headaches,
nausea, dizziness, depressions and rashes to diseases of the lungs, heart, liver, kidneys
and other organs, paralysis and even cancer.
The production, application and disposal of chemical treatments all contribute to
series environmental pollution. Toxic chemicals can enter the food chain and
accumulate in increasing concentrations in the bodies of all living organisms and most
of all, in human beings. Factors such as solar radiation, high temperatures, humidity
and atmospheric pollutants can transform certain preservatives into other even more
dangerous substances.
Means of protecting timber
Timber can be protected by:
The reduction of moisture content to less than 20 per cent, below which timber is
usually immune from fungal attack.
The avoidance of distortion and splitting. This weakens the structure. Splitting also
provides access fort insects.
The protection of vulnerable surfaces. This includes the end of beams, concealed
surfaces, or those exposed to climatic elements.
The exclusion or quick removal of water. This prevents deterioration due to excessive
expansion and contraction as a result of frequent wetting and drying.
The use of natural preservatives, minimising the development and spreading of fire,
fungi and insects.
These methods should be used together to protect timber effectively, although the
relative importance of each will depend of local circumstances.
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