What is CLS Timber? Here’s Everything You Need To Know

Our comprehensive guide will answer all your questions about CLS timber, covering its definition, where it can be used, and the sizes it comes in, helping you decide if it’s right for your next project.

What is CLS Timber? 

Typically made from pine, fir, or spruce, CLS timber is a kiln-dried softwood known for its graded strength and smooth, rounded edges. These features make it easy to handle and work with while remaining reliable with its durability.

CLS timber stands for “Canadian Lumber Standard”, as it was originally produced in Canada. As it gained popularity worldwide, much of it began to be sourced from Europe; at Covers Builders Merchants, we import all of our CLS timber from Sweden and Germany. 

What Is CLS Timber Best Used For? 

CLS timber is ideal for projects such as framing in wooden building construction, studwork, carcassing, and interior partition walls. Its consistently straight form, good graded strength, and ease of use make it perfect for these jobs. CLS timber offers reliability when you need it most with internal structural projects, ensuring high-quality results. 

Is CLS Timber Treated?

CLS timber is typically pressure-treated with preservatives, which penetrate deeply into the wood, making it longer-lasting as it is resistant to moisture, decay, and insects. This treatment makes it particularly useful in areas where the wood might be exposed to damp conditions, ensuring the timber's long-term structural integrity. 

What are the Benefits of CLS Timber? 

The benefits of CLS timber make it a great choice for many construction projects.

• Kiln-dried: This process removes moisture to add strength and prevent warping or cracking, making it useful across all building work.
• Strength graded: Proper strength grading ensures reliable performance for structural applications by categorising timber based on its load-bearing capacity, with grades like C16 and C24 indicating higher strength and consistency.
• Planed planks with rounded edges: This provides a smooth and even finish so the timber is ready and safe to use in your project.
• Treated: This ensures moisture and insect resistance perfect for framework or exterior applications. 
• Versatile: CLS is suitable for a range of structural construction projects like framing, studwork, carcassing, partition walls, and external structures. ​

Can CLS Timber Be Used Outside? 

As a result of it being pre-treated, CLS timber can be used for outdoor applications. It can withstand moisture, rot, and insects, making it a great choice for exterior projects, such as decking, fencing, sheds, and more. It’s important to consider that for long-term external use, CLS timber will need some extra maintenance with preservatives and sealants, especially if you want it to be completely waterproof. There are also UV-protective and waterproof paints that can help protect your timber project as well as decorate it. 

What Sizes Does CLS Timber Come in? 

CLS timber comes in a wide range of dimensions to fit exactly your project’s needs. At Covers Builders Merchants, our CLS timber comes in these sizes: 

What Are the CLS Timber Strength Grades?

When timber is strength-graded it’s assessed for its load-bearing capacity, structural integrity, and durability. The assigned grades are important for allowing you to choose the appropriate timber strength for your project. 

CLS timber typically comes in C16 and C24 strength grades. Which strength grade you need will depend on the project you intend to use it for. C16 timber will work for most applications and is the cheaper option, however, if you need extra strength for load-bearing projects, C24 is recommended. See the table below with the specific requirements for both types decided by the British Standards BS 5268-2:

Is Our CLS Timber Sustainable? 

Making environmentally conscious choices when selecting timber is a top priority for many people. If you’re wondering whether CLS timber is an eco-friendly choice, the answer is that it depends on where it has been sourced. At Covers Builders Merchants, our CLS timber comes from managed forests which means that there is a program in place to encourage sustainable use, prioritising regeneration, and remaining considerate of local wildlife. 

Explore Our Range of CLS Timber

CLS timber is a versatile option for a wide range of projects. Whether you need it for framing, studwork, or outdoor applications, it is a high-quality, reliable timber choice. Explore our CLS timber selection now and get started on your next project.

As an independent, family-owned business, we believe in the value of quality and expertise. With over 175 years in the industry, you can trust in our specialist knowledge and top-quality customer service. Find your nearest Covers depot for all your building needs.