Durability Class
Classification of the natural resistance of wood to decay.
The durability class according to DIN EN 350 describes the natural resistance of a wood species to wood-destroying fungi. The classification ranges from class 1 (very durable) to class 5 (not durable). Typical values in stair construction: black locust and thermally modified timber achieve class 1–2, oak class 2, larch class 3–4, beech and maple class 5. For outdoor stairs, at least class 3, preferably class 1–2, should be chosen.