Preservative treatment for timber - a guide to specification

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The first decision to be made regarding preservative treatment is whether the use of a naturally durable species will satisfy the durability requirements or whether treatment is needed. This Wood Information Sheet aims to guide the specifier through the process necessary to reach a decision that will result in a timber component that is fit for purpose.

Aspects considered include service factors, desired service life, the in-service environment, natural durability and regulated products.

This Wood Information Sheet (WIS) guides the specifier through the process of:

  • Deciding whether a preservative treatment is required to protect a timber product
  • Specifying where a treatment is required
  • Specifying an appropriate treatment to ensure that a timber component is fit for purpose with regards to its durability.



  • Key Standard and guide for specifiers
  • Factors influencing wood decay and the need for preservative treatment
  • Specifying an appropriate preservative treatment
  • Post-treatment


This Wood Information Sheet was revised in April 2017 and changes have been made to reflect the update of standards BS EN 335 and BS EN 350.

Suggested Reading

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