The eventual end use of preservative treated timber is classified into one of the five main categories shown in the table below. These Use Classes, defined in BS EN 335-1, are based on the potential threat to the timber from decay or insect attack in its eventual application.
For instance, internal building timbers in Classes 1 and 2 will be under less threat than timbers used externally in ground contact - Use Class 4. Therefore, Use Class 4 timbers will require a higher degree of protection. Next generation TANALISED pressure treated timber can be used with total confidence in Use Classes 1 - 4.
Always ask your supplier which Use Class the timber is treated to, particularly for ground contact applications.
Use Classes – BS EN 335-1
UC 1 - Internal, dry (eg. Upper floor joists)
UC 2 - Internal, risk of wetting (eg. Tile battens)
UC 3 coated (3.1) - Outdoors, coated, above ground (eg. Soffits/Cladding)
UC 3 uncoated (3.2) - Outdoors, uncoated, above ground (eg. Cladding/Fence rails)
UC 4 - Direct soil or fresh water contact (eg. Fence posts)