CEN/TC 38/WG 21 - Durability - Classification ( Use classes-natural durability)

This European Standard gives guidance on methods for determining and classifying the durability of wood and wood-based materials against biological wood-destroying agents.
The methods can be applied either to individual wood species, batches of wood and processed wood-based materials, including heat-treated, preservative-treated wood and modified wood. However, this standard is not intended to replace testing of the efficacy of biocides.
The wood-destroying agents considered in this standard are:
—   wood-decay fungi (basidiomycete and soft-rot fungi);
—   beetles capable of attacking dry wood;
—   termites;
—   marine organisms capable of attacking wood in service.
Data on the biological durability of selected wood species considered of economic importance in European countries are presented in Annex B (informative), which also provides information relating to their geographical origin, density, sapwood width and treatability.
NOTE   Treatability, durability to disfiguring fungi, permeability to water and performance in use of wood and wood-based materials are also important issues. However, because standardized methods aiming to assess and classify these factors do not exist and/or have not been extensively experienced yet, preliminary guidance is given in Annex C (informative) for the classification of wood treatability with aqueous wood preservatives, Annex D (informative) for the classification of the permeability to water, Annex E (informative) for the durability to disfiguring fungi, and Annex F (informative) for the classification of performance.

This European Standard is applicable to solid wood and wood-based products.
This European Standard defines five use classes that represent different service situations to which wood and wood-based products can be exposed. This standard also indicates the biological agents relevant to each situation.
A use class is not a performance class and does not give guidance for how long wood and wood-based product will last in service.

This European Standard contains terms relating to wood durability and the definitions of these terms.

This document provides the basis for selecting the preferred equivalent terms for the drafting of future European Standards and other documents on natural or conferred durability of wood and wood based products.
NOTE    A new list of terms relating to environment, health and safety aspects will be prepared and will be dealt within an other European Standard.

This document provides the basis for selecting the preferred equivalent terms for the drafting of future European standards and other documents on natural or conferred durability of wood and wood based products.

This part of EN 335 defines five use classes which represent different service situations to which wood and wood-based products can be exposed. This part of EN 335 also indicates the biological agents relevant to each situation.
Annex A gives information on these biological agents.

This part of EN 335 offers guidance on the application of the use classes, as defined in Part 1 to solid wood of EN 335, in relation to the biological agents that can attack solid wood and solid wood panels.
NOTE   Due to their specific behaviour against biological agents, solid wood panels are mentioned in this part and not in Part 3 of EN 335.
This Part shall be used in conjunction with Part 1 of EN 335.
Annex A gives information and guidance for the user to determine the appropriate use class and to select a suitable level of durability (either natural or conferred by preservative treatment). It does not give guidance on protective measures other than preservative treatment.