Stockdale Fencing | Newt, otter, and small animal fencing | Stacked timber

When buying and using preserved timber, it’s important to realise that not all treated wood is the same. The technical standards for wood preservation (set out in BS 8417) highlight different levels of protection into Use Classes so that treated wood with the correct level of preservative protection, at the correct level of penetration, is used in the correct setting.

  • Not all treated wood is the same.
  • Technical standards for wood preservation highlight the different levels of protection.
  • Wood with the appropriate level of protection for its location should be used.

Establishing the Use Class of timber necessary before starting a project ensures that wood treated for external use only is not used internally, and that wood suitable for interior use only is not used externally. In either of these instances the timber used would not be fit for purpose.

There are 3 main Use Classes for treated wood as set out by the WPA Code of practice for Industrial Wood preservation:

Use Class 2 is suitable for use inside, above ground, or for areas covered by a damp proof course. For example, timber used in construction such as sole plates, internal joists, roof battens or tiling battens.

Use Class 3 is suitable for outside, above ground use such as external construction timber that is uncoated. For example, decking boards, external cladding, or fence rails.

Use Class 4 is suitable for use in areas where the wood is permanently wet and providing exterior structural support, just providing exterior structural support, permanently wet with fresh water, actually in contact with the ground, or in very close contact with the ground. For example, in playground equipment, beams, deck posts and  joists, and fence posts.

So, as fence posts are providing exterior structural support in supporting the fence, are in permanent ground contact, near ground contact, or even in fresh water, use of Hazard Class 4 timber is essential. To use anything less for fencing not only compromises safety, but it will also undoubtedly reduce the service length of the fence.

At Stockdale Fencing we only use Hazard Class 4 timber. This is tanalised timber suitable for outdoor use and we only source our timber from reputable suppliers where timber can be traced back should you ever have any issues.