When you are buying a timber shed or garden building, you will almost always see “pressure-treated” or “dip-treated” mentioned in the product description. Both protect the wood against rot and decay, but they do so in very different ways and to very different depths — and that difference has a real effect on how long your building lasts and how much maintenance it needs. Here is a plain-English guide to both.
What is pressure treatment?
Pressure treatment (sometimes called tanalising, after one of the most widely used chemical processes) works by placing the timber in a sealed chamber, drawing out the air, and forcing preservative deep into the wood fibres under pressure. The result is a building material that is protected throughout its thickness, not just on the surface.
Because the preservative is locked into the cell structure of the wood, it cannot simply wash away in rain or evaporate in the sun. Pressure-treated timber typically carries a long manufacturer’s guarantee — often 15 years against rot and fungal decay — and can last a generation or more with basic maintenance.
What is dip treatment?
Dip treatment involves immersing timber briefly in a preservative bath, or brushing or spraying the preservative onto the surface. The product penetrates only a few millimetres at most. While this is enough to offer some protection when the wood is new, it is a surface coating rather than a deep treatment, and it needs renewing more regularly as it weathers and wears.
Dip-treated timber is generally less expensive to produce, which is why you will find it in budget shed ranges. It is not without value — a well-maintained dip-treated shed can still have a decent lifespan — but it asks more of the owner to keep it protected.
Pressure-treated vs dip-treated at a glance
| Feature | Pressure-treated | Dip-treated |
|---|---|---|
| Depth of penetration | Through the timber | Surface only (a few mm) |
| Typical protection | 15 years+ with basic care | Shorter; needs regular top-up |
| Ongoing maintenance | Topcoat every 3–5 years | Re-treat every 1–2 years |
| Typical cost | Higher upfront | Lower upfront |
| Best for | Long-term value, low maintenance | Budget builds, shorter lifespan |
Does pressure treatment mean I never need to do anything?
Not quite. Pressure treatment protects the timber from rot and fungal decay from the inside out, but it does not stop the surface from greying, weathering and eventually looking tired. A decorative topcoat — a quality wood stain, spirit-based preservative or paint — keeps the building looking its best and adds an extra layer of weather resistance. Applied every few years, this is a modest task that extends both the appearance and lifespan of even the best-treated timber.
What does Rutland Sheds use?
All Rutland Sheds garden buildings use pressure-treated timber as standard. It is the specification that makes most sense for a building you want to last — and it underpins the confidence we have in the durability of what we sell.
Frequently asked questions
Is pressure-treated timber safe for pets and plants?
Modern pressure-treatment processes use water-based compounds that are far safer than older solvent-based preservatives. Once dry, pressure-treated timber is considered safe for gardens, including where children and pets have access.
Can I paint over pressure-treated timber?
Yes — once the timber has had a chance to dry out after treatment (usually a few weeks), you can apply a stain, paint or topcoat in your chosen colour. Check that the product is compatible with treated timber.
Why does some pressure-treated timber look greenish?
The greenish tint is a normal result of the preservative chemicals. It fades as the timber weathers and is usually gone within a season or two, particularly if you apply a coloured topcoat.
Choosing a building built to last
If you are comparing sheds and wondering why prices differ, the treatment specification is often a big part of the answer. Take a look at our range of garden sheds — all built with pressure-treated timber — or get in touch for straightforward advice on the right specification for you.