What is CLS Timber? CLS Features & Uses

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What is CLS timber? What does CLS timber mean?

CLS stands for Canadian Lumber Standard, and it is usually made from a kiln-dried softwood timber such as pine, fir or spruce. Originally manufactured in Canada, but now produced globally, it’s an ideal wood for building strong, durable and sturdy timber frames in construction.

CLS stud work and framing timber can be made out of various types of wood, and is often made in the UK or from European timber sources.
 

What type of wood is CLS timber?

CLS timber can be made from softwoods such as fir, spruce or pine, and traditionally it is kiln dried to make it hard-wearing. CLS is planed and pre-treated, so it’s ready to use in construction, and it often has a classic rounded edge which makes it straightforward to use and safe to work with. 

What size is CLS timber?

Canadian Lumber Standard beams and timber battens come in a wide selection of sizes and lengths, in both C16 and C24 strength varieties, designed for different projects and uses. Travis Perkins stock a range of pre-cut CLS studwork timber, from 2.4m to 6m lengths, in thicknesses from 38mm to 75mm. CLS is also easy to cut to size if needed. By having a choice of lengths and widths, it helps to reduce wastage and keep your materials cost down. 
 

What is CLS timber treated with?

Most CLS timber is kiln dried before being pressure treated, as well as being treated with a pesticide to ward off insects and fungus. The kiln drying process removes moisture and adds strength to the wood, before being planed and rounded at each corner, so it’s all ready to use for stud work and internal structural use. The preservative treatment gives the wood resistance to moisture, as well as being strong and hard wearing.
 

What is CLS timber mainly used for?

CLS timber is strong and versatile, making it perfect for partitioning, stud wall construction, floor joints, door and window frames, roof battening, carcassing and internal structural work in new homes and extensions. It’s primarily used during the first fix, when the room layout, door frames and roof frames are put in. It is most commonly used indoors, being a softwood, but occasionally with additional treating methods it may be used outdoors too.

CLS comes in two strength grades, which offer different pros and cons: 

• C16 - slightly less strong but usually better value

• C24 - stronger but can be more expensive

What are the benefits of CLS timber?

CLS timber is famed for being not only strong but versatile, easy to work with and safe to use. The kiln drying process removes a lot of moisture, making it less likely to warp or decay. It comes in a wide variety of lengths and sizes to suit your project. 

CLS is treated after being dried, which saves time in construction as well as making it moisture resistant and naturally repellent to insects and wood worm. Its lack of knots make it more fire resistant than some other timbers. The lightweight structure and rounded edges make it simple and safer to work with, as well as long lasting and reliable for resilient internal timber structures in most climates.

Traditionally, CLS was made for building timber structures in the Canadian wilderness, so it’s easy to imagine that its strength is designed to hold up to changing temperatures without degrading.
 

CLS Timber: FAQs

What does CLS stand for (timber)?

CLS stands for Canadian Lumber Standard, and it is usually made from a kiln-dried softwood timber such as pine, fir or spruce. Originally manufactured in Canada, but now produced globally, it’s an ideal wood for building strong, durable and sturdy timber frames in construction.

What is the difference between CLS and C16 timber?

C16 timber is a strength variety of CLS (Canadian Lumber Standard) wood, and is considered less strong than C24 grade CLS. However, with its round planed edges, strength and usability, it’s ideal for framing and stud wall construction.
 

What is the difference between CLS and C24?

C24 timber is a strength variety of CLS (Canadian Lumber Standard) wood, and is considered stronger than C16 grade CLS, with fewer knots. This makes it ideal for when larger loads are required, such as for load bearing beams.
 

What does CLS timber mean? 

CLS timber (Canadian Lumber Standard) is a structural timber which is popular for internal construction in buildings and homes. It is pre-treated and comes in a variety of strengths and sizes for different uses. CLS timber is made from special softwood material, including fir, spruce or pine, which is kiln dried and treated for strength and durability.

What is the difference between CLS and 4x2?

4x2 is the finished size of the timber (it can also be referred to as 38 x 89mm or 4" x 2"), and the term CLS refers to the style of treated softwood (Canadian Lumber Standard). CLS can come in a variety of sizes to suit its use, from framing to stud walling.
 

Can you use untreated CLS outside?

CLS is a softwood, which is generally recommended for internal use. However, if the timber is additionally treated to withstand the elements - such as by sealing and painting it to prevent rotting and decaying - it is possible. Experts often recommend C24 grade CLS timber for use outside, with regular maintenance to help maintain its strength and appearance.

What is CLS studwork timber?

CLS studwork timber can be made from softwoods such as fir, spruce or pine, and traditionally it is kiln dried to make it hard-wearing. CLS is planed and pre-treated, so it’s ready to use in construction, and it often has a classic rounded edge which makes it straightforward and safe to work with.

Disclaimer: The information contained on this page is intended as an overall introduction and is not intended as specific advice from a qualified professional. Travis Perkins aims to avoid, but accepts no liability, in the case that any information stated is out of date.