In buildings, wood materials are subject to decay. Decay is defined as the state or process of rotting or decomposition [a]. The most common types of wood rot are brown, white, and soft [b].

Brown Rot
[1] Brown Rot

Brown Rot is characterized by wood color becoming lighter prior to becoming dark brown and by cracks forming in brick shapes across and along grains. When dry, very decayed timber will crumble to dust. The dry-rot fungus is a common species of brown rot. [b]

White Rot
[2] White Rot

White Rot can be observed in forests as the disk-shaped growths protruding from the sides of trees. It can also occur on timber in buildings. Strength losses are not significant until late stages of decay. [c]

Soft Rot
[3] Soft Rot

Soft Rot was first characterized as a soft, decayed surface of wood in contact with excessive moisture. However, soft rots can occur in dry environments and may appear similar to brown rot. Common places for soft rot include fence posts, telephone poles, and window frames; essentially, soft rot can be found wherever timber comes in contact with moisture regularly. Presence of nitrogen in the wood or surrounding environment contributes to the development of soft rot. [b]

Wood rot can be prevented by ensuring that no moisture can get past the skin of the building. Problems occur when moisture gets in and can’t get out. Making sure all wood surfaces are painted or sealed and caulking all seems in windows, doors, and exterior vents. Decay-resistant and pressure-treated lumber is also resilient against wood rot. Dry rot can be treated by epoxy, which kills the fungus and fills in the channels, thus restoring structural integrity.