Dip-treated or pressure-treated?

This decides how much work you're signing up for over the next ten years. It's worth two minutes.

The three options

Untreated. Bare timber. You must treat it yourself, usually within weeks of it being built, and then keep doing it. Cheapest up front, most work, and the easiest to get wrong.

Dip-treated. The panels are dipped in a coloured preservative at the factory. It's a head start, not a finish. Expect to re-treat within the first year and then annually.

Pressure-treated (also called tanalised). Preservative is forced into the timber under pressure rather than sitting on the surface. The most durable option — rot protection is often quoted up to twenty years. Costs more, asks far less of you.

Which to choose

If you'll genuinely get a brush out every spring, dip-treated is fine and saves money.

If you know you won't, pay for pressure-treated. It is cheaper than replacing a rotten shed in year six, and it's the single upgrade most likely to still be paying you back in a decade.

Read the guarantee conditions, not the headline

"10-year anti-rot guarantee" appears all over this market. What it usually doesn't say on the front is that it's conditional on you treating the building annually and keeping records.

A guarantee you've voided by doing nothing is not a guarantee. Where a manufacturer states conditions, we list them on the product page — and if you'd rather not have that commitment, that's a reason to choose pressure-treated.

One thing people miss

Whatever you buy, treat the cut ends and the underside of the floor before the building goes down on the base. Those are the faces that take the most moisture and the ones you'll never be able to reach again.