Use Classes, (formerly referred to as Hazard Classes), have been introduced to help specifiers and users of treated timber, identify and confirm the level of protection their timber requires for a particular end use.

The table below shows the main use classes that can be specified.

Generally a greater degree of protection is required as the Use Class increases. These Use Classes are used throughout the industry to provide a common understanding of the level of protection that is required for a given application.

Use Classes:

1	Internal, dry e.g. upper floor joists
2	Internal, risk of wetting e.g. tile battens
3(A)	Outdoor, coated, above ground e.g. window frames
3(B)	Outdoor, uncoated, above ground e.g. fence rails
4	Direct soil or fresh water contact e.g. fence posts