Wood rotting fungi obtain their food by breaking down wood cell walls, causing loss of strength. They cannot utilise wood at or below 20% moisture content and will not occur in building timbers unless poor design or building defects result in water ingress or condensation.
Not all fungi cause wood rot. However, the presence of fungal growths indicates damp conditions exist and are suitable for the development of wood rot.
Wood rot in buildings can be divided into two groups depending upon their effect on the timber.
White Rots cause the wood to become lighter in colour and fibrous in texture without cross-cracking.
Brown rots cause the wood to become darker and to crack across the grain. When the wood is dry, severely decayed timber will crumble to dust.
Except for one brown rot, Serpula Lacrymans, which is commonly called dry rot, all white rots and brown rots are referred to as wet rots.
It is not necessary to distinguish between the many species of wet rot which can be found in timbers, as the same remedial measures are required for all of them.