4x2 Timber

4x2 Timber is a very popular size of Timber joist, and used for a variety of purposes, particularly decking and garden buildings, as well as in the construction of timber frame buildings.

We sell a selection of 4x2 structural timber - both treated and untreated, and also 4x2 CLS which is untreated and graded to C16. CLS timber has a slightly smaller profile than standard 4x2 timber joists, as it is regularised on all sides.

In the UK, regularised timber is most commonly classified into two grades: C16 or C24. The "C" signifies the wood type, specifically Conifer. The number (24/16) indicates the bend strength - which is based on factors such as imperfections and knots. While C24 is the stronger grade, C16 remains exceptionally strong and is used in numerous wall and roofing applications.

CLS stands for “Canadian Lumber Standard” as it was originally sourced in Canada. Nowadays it is grown and sourced from various countries including grown here in the UK, but CLS is still used as a common name to identify the product. CLS is typically used for structural projects such as stud walls and partitioning, and is regularised on all sides, giving it a smaller profile than standard 3x2 timber by a few millimetres.

If you are not familiar with timber sizing, the measurements of 4x2 timber may be confusing. "4x2" refers to the measurement in inches, the traditional way of measuring timber. This roughly translates to 47mmx100mm. However, in reality, most 4x2 structural timber is regularised to achieve a smooth and even surface along the length of the timber, which means that the dimensions are usually a few mm smaller - closer to 45mm x 95mm. Additionally, CLS Timber is finished on all sides which means it is a few mm smaller again - more like 38mm x 89mm.

Our Treated 4x2 Timber is treated to UC2 and is designed for use in outdoor construction, though timber in direct contact with moisture may need further treatment. Our CLS and untreated 4x2 timber is more typically used indoors in the construction of timber frame structures, although treated timber can also be used, as it simply gives it additional resistance to moisture and pests.