When used properly, wood is a very durable material. In order to guarantee the long service life of wooden constructions, the construction planning must include a wood preservation concept, consisting of design and construction measures. Where applicable, preventative chemical wood preservation, construction process organisation, as well as the right selection of material should be considered.
- In general, wood preservation during construction should be given priority.
- Chemical wood preservation measures should be avoided for interior applications.
The European standards EN 335 regulate wood preservation. National standards must also be taken into consideration (e.g., DIN 68800-1). Given that, chemical wood preservation can only prevent the risk of fungal and insect infestation, but not shape modifications and their consequences. Even the most thorough chemical wood preservation may not lead to negligent design and construction.
Where possible, and economically and environmentally reasonable, chemical wood preservation may be avoided by using resistant wood species.
The main focus should be on avoiding leakages in the building shell, so as to exclude the possibility of structural damage due to
- ingress of unacceptable moisture by leakages in the outer shell
- Condensation on cold outer layers due to ingress of warm, moist indoor air (convection)must be excluded.
Important construction and design measures
Consideration for the main weather direction when selecting the type of construction and the configuration (e.g., protection of the façade through suitable roof overhang, canopies).
- Special protective measures on the weather side for sensitive components such as windows
- Avoiding direct contact with moist components and the ground, such as splash water, drifting snow, etc.
- Avoiding thermal bridges due to building material and geometry – risk of condensation.
- Use of dry timber. In fully insulated components, solid structural timber, glulam, or I-Beams and wood-based materials with moisture content of 15 ± 3% should be used.
- Load-bearing wooden components should be made inaccessible for insects accessible for inspections. Under roofs, the use of kiln dried wood is a proven wood preservation measure against damage caused by insects.
- Extremely careful configuration of the airtightness layer.
- Vapour-permeable components with high evaporation potential should be given priority.