What is UC4 Timber?

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What is UC4 Timber?

Choosing the Right Timber

Any timber - whether fencing, railway sleepers or other landscape timber - that comes into contact with the ground is exposed to moisture on an ongoing basis. If left untreated, it will quickly begin to deteriorate. 

If you don't choose the right kind of timber, you run the risk of increased lifetime costs, premature failure/rotting and expensive re-installation. 


Untreated vs Pressure Treated Timber

Oils and preservatives can be used to treat untreated timber, but they usually need to be applied regularly to ensure a decent barrier is maintained between the moisture and the wood. Most manufacturers recommend at least annual treatment. 

This can be laborious and time-consuming and is often dependent on the timber being dry at the outset.

Instead of faffing with treating the timber yourself, we recommend purchasing pressure-treated softwood. It should be used in any project where timber is exposed to the elements and is in contact with the ground.


UC4 Pressure Treated Timber

However, if you really want that peace of mind that the timber is durable, go for pressure-treated timber that's also treated to British Standard 8417.

Leading sawmill and timber product manufacturer Charltons Timber Store have a fantastic range of 'Longlast' products that meet BS 8417. Everything in the range is guaranteed for a whopping 15 years!

Timber that meets this standard is also known as 'Usage Class 4' timber, or UC4 for short. To meet the standard, the timber has to be prepared correctly. Whilst this may vary slightly between manufacturers, this is how Charltons' prepares theirs:

  • Species - the Longlast range only uses Redwoods due to its natural durability.
  • Drying -  by naturally air drying the timber to 28% moisture content, the pressure treatment is then absorbed and retained through the sapwood to the durable heartwood.
  • Preparation - layers of timber are separated by spacers to allow for consistent drying and treatment right through the pack.

Paying that little bit more for the timber in the first place means you won't face even more extra costs in the long term. Makes sense, right?



As a Charltons stockist, we have an entire page dedicated to their products - including those from the UC4 Longlast range. You can browse Charltons products here - any products in the range will state 'UC4 Longlast Range' in the product description.

If you need more information or advice on the right choice of timber for your next fencing project you can get in touch here.