Rotfasthet

Rotfasthet is a term used in timber science and building to describe a material's resistance to rot, i.e., decay caused by wood-destroying fungi and other organisms. It encompasses natural durability and the effectiveness of protective measures, determining whether timber can withstand exposure to moisture, soil contact, and outdoor conditions without significant loss of strength or integrity. In practice, rotfasthet is a key criterion when selecting wood for exterior applications and for design and maintenance planning.

Natural durability varies widely among wood species. Heartwood often contains extractives that inhibit fungal growth, giving higher rotfasthet than sapwood. Standardized assessments categorize wood into durability classes, commonly from very durable to not durable, based on laboratory and field tests that expose samples to decay fungi under controlled conditions (for example, EN 350-2). These classifications guide use in different exposure classes, such as above ground, in ground contact, or submerged.

Moisture, temperature, oxygen availability, and nutrient access strongly influence rotfasthet. Fungi require relatively high moisture content to thrive, so wood kept dry or protected tends to resist rot even if biologically susceptible. Environmental design, moisture barriers, and drainage are important complements to inherent or treated rotfasthet.

Enhancing rotfasthet can involve selecting naturally durable species, applying chemical preservatives through pressure treatment, or employing modern alternatives like waterborne preservatives or thermal modification. Surface coatings and physical barriers also help by limiting moisture ingress. Maintenance, ventilation, and inspection are essential to sustain rotfasthet over the life of timber structures.

Rotfasthet remains a central consideration in timber construction, influencing material choice, treatment strategies, and long-term performance.