Wood Natural durability classifications are based on the woods ability to resist degradation to wood destroying fungi. Wood destroying fungi and insects are the most significant threats to wood or timber durability in the UK. Insects tend not to be a serious risk in the UK as wood destroying insects prefer the warmer climates, e.g. Mediterranean climates. Moreover, insects tend to attack the sapwood or heartwood that has already been colonised by rot.
Fungi thrive well on high moisture content that has been sustained for a long time in wood; it is essential to keep the wood at 22% MC or less so that the fungi cannot survive it is the prolonged and sustained high moisture content that tends to create the issues as this allows favourable conditions for spores to colonise timber or wood products.
In construction applications such as timber flooring, timber cladding, timber decking – moisture is one of the factors that are easier to control and this is key to wood preservation from biological decay. On areas that are exposed to a lot of moisture, it is essential to ensure that the elements or components are well detailed to allow for quick drying of the wood through consideration of factors like drainage, airgaps, deflection of the rain or water and also using suitable materials species, decking fixings, cladding fixings, decking profiles, cladding profiles finishes and treatments etc.
Not all fungi found on wood causes decay, some fungi will only cause discolouring or staining. Fungi that are most common for wood decay are brown rot ( found mainly on hardwoods), white rot ( found mostly on/ hardwoods and softwoods) and soft rot ( found on both hardwoods and softwoods).
If there is a need to treat timber there is a basic guide to ensure that timber has been well treated and fit for purpose.
