Timber decking guide - Timber preservation

Softwood species classified as semi or non-durable should be industrially pre-treated with a preservative process to provide long life. Today, wood is preservative treated according to the "Hazard" (risk of decay) it faces in use. Timber intended for use inside a building will not be treated to the standard required for a deck component like a post or joist that is to be in contact with the ground or water. These components should be treated in accordance with Hazard Class 4 to ensure they will provide long life in wet conditions. Components treated in accordance with Hazard Class 3 should be used for all other elements that are not in ground contact.

If there is any doubt about the level of treatment a component has had, ask your timber supplier to confirm in writing the Hazard Class your timber is suitable for.

Brush-applied wood preservatives or dip treatments are not suitable for the long-term protection of timber used for decking and other outdoor landscaping applications and should not be used.

Timber is made highly durable in a treatment plant like this.

As well as preservative protection some timber also comes ready treated with a water repellent that helps further protect the wood from weathering.

When buying any timber component for decking look for the DeckMarkTM quality assurance symbol. This is your proof that the product has been independently assessed by the TDA. DeckMarkTM products are widely available throughout the UK through timber and builders merchants.

For a list of quality assessed product suppliers click here