mjukröta

Mjukröta, or soft rot, is a form of wood decay caused by certain fungi that colonize timber in damp or wet conditions. It primarily degrades cellulose and hemicellulose in the wood cell walls, leaving lignin relatively intact, which weakens the structural integrity and produces a soft, crumbly texture. Soft rot can occur at lower moisture thresholds than some other wood-decay types, making timber that is damp or waterlogged particularly vulnerable.

There are two commonly described decay patterns in soft rot. Intracellular soft rot involves fungal hyphae invading the interiors of wood cells and breaking down their contents, while extracellular or cavity-forming soft rot erodes cell walls to create cavities or a sponge-like texture. Symptoms include soft, damp areas in the wood, pale to brown discoloration, and, in high humidity, the appearance of fungal mats or powdery growth. In severe cases, the wood may crumble and lose strength.

Occurrence and risk factors include timber in contact with soil, wood exposed to persistent moisture, and indoor environments with high humidity. Soft rot can develop in many wood species and is often observed in construction timber, utility poles, and marine or submerged timbers.

Prevention and control focus on moisture management and protective treatments. Strategies include improving drainage and ventilation, using moisture barriers, and selecting durable or treated wood. Protective coatings and preservative treatments containing copper-based compounds or borates can enhance resistance, as can maintaining drying and conditioning of timber before use. Proper design to avoid prolonged moisture exposure remains a primary preventive measure.

Mjukröta remains a notable concern in damp climates and in structures where wood experiences persistent moisture, contributing to maintenance costs and structural degradation if not addressed.