If you have ever wondered why some timber shrugs off years of British weather while other boards rot within a season, the answer usually comes down to one thing: pressure treatment. Here is what it is, why it lasts, and how to get the best out of it.
What is pressure-treated timber?
Pressure-treated timber is softwood that has had a wood preservative forced deep into the grain under high pressure inside a sealed vessel. Rather than sitting on the surface like a coat of paint, the preservative is drawn right into the fibres, protecting the timber from the inside out.
Why does it last so long?
Untreated softwood left outside is a feast for fungi and insects, and once rot takes hold it spreads quickly. The preservatives used in pressure treatment make the timber far less appealing to the fungi that cause decay and the insects that bore into it. That means fence posts, decking and landscaping timber can last many years longer than their untreated equivalents.
Choosing the right treatment level
Not all treated timber is equal. Treatment is graded by “use class” depending on where the timber will live. Timber that sits above ground, such as fence rails and decking boards, needs a lighter treatment than timber in permanent contact with soil or water, such as fence posts and sleepers, which need a heavier ground-contact grade. Always match the treatment to the job, and use the higher grade wherever the timber touches the ground.
Getting the best from it
A few simple habits go a long way. Whenever you cut or drill treated timber you expose untreated wood in the middle, so brush a coat of end-grain preservative onto every fresh cut. Use corrosion-resistant fixings such as stainless steel or hot-dipped galvanised, as the preservatives can react with ordinary steel. And let freshly treated timber dry out before you paint or stain it.
Need a hand?
We stock a full range of treated timber for decking, fencing and landscaping, along with the preservatives and fixings to go with it. Pop into Richards Builders Merchants and the team will help you pick the right grade for your project.