7th Dec 2022 -

CLS timber has become a lot more popular in the UK in recent years and it’s often the wood of choice for internal structuring jobs. In this piece, we’ll look at exactly what CLS timber is, its benefits, common uses and, of course, what CLS actually stands for

What is CLS timber?

CLS timber is created from softwoods like fir, pine or spruce and the CLS used in the UK is typically sourced from Scandinavian countries. The wood is kiln-dried for extra stability, reducing the amount of moisture it contains, and then treated with pesticides to protect it from insects and decay. Finally, CLS timber is surfaced on all four sides to create rounded edges, giving a finish that’s smoother than a 90s R’n’B track.

Going by the grading standards set by the European Standard BS EN519, you’ll tend to find CLS timber strength-graded at either C16 or C24. While similar in appearance, C24 is the stronger of the two, which is usually reflected in the price. We sell both types here at Building Materials — feel free to browse our full range of CLS timber.

Need CLS Timber For Your Next Project?


    • Ideal for wall partitioning and studwork
    • Kiln dried for extra stability
    Price from: £4.32 £5.18

    • Ideal for general construction, fencing, garden and leisure timber applications
    • Pressure-treated
    Price from: £4.20 £5.04

    • Ideal for general construction, fencing, garden and leisure timber applications
    • Pressure-treated
    Price from: £4.20 £5.04

View All CLS Timber

What does CLS timber mean?

Canada has brought us so much, from maple syrup and ice hockey to Ryan Gosling and, er, Justin Bieber. Another thing we can thank them for is CLS Timber. Short for Canadian Lumber Standard, the wood was initially used to build resilient homes in the Great White North, before becoming popular elsewhere in the world. Pretty cool, eh?

What are the advantages of CLS timber?

Exceptional durability

CLS timber is a lot more durable than other types of wood timber, making it great for both construction and internal structural work. This also makes it much more cost-effective over time — a win-win!

Easy to transport and safe to handle

CLS timber is much easier to transport than its untreated counterparts, and it’s safer to handle thanks to its round edges. Its unrounded, unshaven edges also make it more prone to causing damage to walls, furniture, and even people if they take a knock.

Aesthetically pleasing

Because of its surface finish, CLS timber is very easy on the eye, which might explain why it’s so commonly used for internal projects.

Available in lots of different widths and lengths

CLS timber is available in various widths and lengths, reducing the time you’d otherwise spend cutting it to size. Plus, since there’s no wasted timber, you’ll only need to buy what you need, with no pesky planks left over.

Here at Building Materials, we have a wide range of CLS timber sizes available, in widths from 75- 100mm and lengths between 2400-4800mm. Contact our team with any enquiries about specific sizes.


How is CLS timber used?

CLS timber is particularly useful for jobs like:

  • Timber framework construction
  • Carcassing 
  • Interior framing
  • Stud walling
  • Building internal partitioning 

Can CLS timber be used outside?

Although softwoods generally aren’t ideal for outdoor use, CLS timber is better suited to this than most, owing to the fact that it’s kiln-dried and chemical-treated. That said, it’s recommended that you treat it further to offer even more protection against the elements. Thankfully, liquid-repelling preservatives paints that block UV rays, and sealers that maintain colour can all be used on CLS timber. For any projects in the great outdoors, choose C24 CLS timber as C16 is really more of an indoor timber.

Quality Timber Delivered Across the UK

We sell a huge range of timber through our website, including professional standard CLS. We're the only location you need for both professional and DIY projects, offering a fantastic selection of products and materials. For professional customers, our trade accounts give you access to a great range of benefits, including product sourcing, express delivery, and trade pricing.

Sign up for a trade account through our website today, or reach out to us through the form below.

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