Brownrot

Brown rot is a form of wood decay caused by certain basidiomycete fungi that primarily break down cellulose and hemicellulose in timber, leaving behind a brown, lignin-rich residue. It is distinct from white rot, which degrades lignin and cellulose more evenly, and from soft rot, which occurs under different moisture conditions. In buildings and other structures, brown rot often arises in damp timber and can spread rapidly, weakening structural integrity if not addressed.

The decay results from enzymatic action that selectively degrades more easily metabolizable carbohydrates in wood. As cellulose and hemicellulose are consumed, the wood becomes dry, brown, and crumbly, frequently showing cubical cracking in the grain. A musty odor and powdery frass may accompany the symptoms, and visible fungal growth or fruiting bodies can appear in favorable conditions. Moisture is essential for brown rot, with growth typically promoted when wood moisture content exceeds about 20%.

Key brown rot fungi include Serpula lacrymans, known for causing true dry rot in buildings, and Coniophora puteana, sometimes called the cellar fungus. Other brown rot species occur in forests and timber products, contributing to the decay of firewood, lumber, and furniture. The progression of brown rot can be rapid under persistently damp conditions and may spread through connected timber in a structure.

Control and prevention focus on moisture management and timely intervention. Reducing humidity, repairing leaks, improving ventilation, and removing or drying affected wood are critical steps. Preventive treatments include preservative coatings such as borates and proper wood selection and construction practices. In established infestations, professional assessment and remediation are advised to safely halt spread and restore structural safety.