CLS timber is a type of timber that is used for internal structural projects. It is created from softwoods such as kiln-dried fir, pine, or spruce, and is surfaced on all four sides to create rounded edges, giving a finish that is smoother than other types of timber. CLS stands for "Canadian Lumber Standard," as it was originally manufactured in Canada and used for building sturdy timber-framed houses there before it became a popular option in the UK and other parts of the world.

CLS timber is versatile and can be used for a variety of internal structural projects, such as timber frame home construction, creating internal partitioning walls, interior framing, and stud walls. Due to its rounded edges, CLS timber is also particularly easy to transport and safe to handle. It has a lack of large knots on its edges, which makes it better able to reduce the spread of potential fire outbreaks. Another benefit to consider is the fact that CLS timber is available in a variety of widths and lengths to choose from, making it a great option for not only minimizing time spent on cutting it to size but also for reducing the cost from timber wastage.