Wood rot is a phenomenon that can affect any type of timber irrespective of where it is used. Recent heavy rains in some of South Africa’s provinces have raised the threat of wood rot.
According to Arch Wood Protection, a leading supplier of timber treatment products, there are different types of fungi that may attack wood.
Staining fungi will result in discoloration of the timber but the damage is only superficial – the strength of the timber is not affected. However, where timber appearance is important, its value can be significantly reduced by this kind of attack.
Staining fungi generally attack under conditions of high humidity and /or where the timber is freshly felled and contains plenty of nutritious sugars. Where infection occurs, the discoloration is usually caused by moulds forming greenish, or black, occasionally yellow, powdery growths. The good news is that moulds can be brushed away and re-infection can be prevented by removing the source of moisture.
Wood rotting fungi, on the other hand, seriously weaken the timber and may render it quite valueless. Wood rot can be very damaging, especially if it gets into roof trusses or other structural installations. Damage can occur in indoor and outdoor installations, whether the timber is above ground or in ground contact.
There are three groups of wood rotting fungi.
Brown rots are so called because they feed on the lighter coloured cellulose content of the wood and leave the darker lignin more or less intact. This type of rot tends to break down the cell walls and the timber becomes powdery in texture. Dry rot is an example of brown rot and can cause serious damage in buildings.
White rots are so called because they feed on both lignin and cellulose, making the timber lighter in colour. This type of rot is often characterised by small white pockets and it causes the timber to become brittle in texture.
Soft rot is prevalent in very wet environments such as in soil. It softens the exposed surfaces of the timber and gradually reaches to increasing depths, causing shrinkage as the outer layers decay.
Treatment with a wood preservative such as Tanalith C (CCA) plays an important role in reducing wood’s exposure to decay. The product offers dual protection – against insect attack and fungal decay.
Fungal protection is provided by the metal-based ingredients, such as copper oxide. Other products, such as Tanalith E, incorporate recycled metal-based ingredients and there are products that use metal-free chemistry as well – replacing the metal-based ingredients with specialised biocide formulations which are organic and are thus biodegradable.
Arch Wood Protection offers these products internationally and will soon launch a new biodegradable product locally.