Treated timber

Timber won't rot if it's kept dry to a moisture content below 20%. When it's used outside, this may not be possible.

There are two solutions to this problem, either you can use a naturally durable timber - such as oak or western red cedar - or you can use a non-durable softwood that's been treated with a suitable preservative.

This Choose and Use sheet details some of the key considerations to be made when deciding between specifying naturally durable or treated timber.

It also contains guides on which components treated timber can be used for, a summary the four different use classes and the different preservative treatments on offer.

Contents:

• Natural durability and treatment considerations
• Where can treated timber be used?
• Use Classes and desired service life
• Treatment processes and preservative chemicals
• Machine treated timber
• Where to go for further help and advice