4x3 Treated Timber C24 Regularised Sawn 75x100mm

Traditionally measured in inches, “4x3” refers to the size of the joist in inches. If you want to know what 4x3 Timber is in mm - the equivalent size is 75 x 100mm. However, as the timber is regularised, this means that to achieve a timber joist that is uniform in size the entire way along the length, the “finished” size can be a few mm smaller than 75x100mm, usually closer to 73mm x 100mm.

The size difference is minimal and in the vast majority of projects will make no difference to your project, and is standard across 75x100, 4x3 regularised timber joists.

Our 4x3 treated timber is graded C24 and is typically used for structural framing applications but can also be used in roofing, floors and other structural projects. Our 4x3 timber can also be used in building decking framing due to it’s superior strength, though it will need further treatment to protect against moisture and pest. 

Our timber joists are often referred to as “regularised” - meaning the lengths of timber are machine-finished to achieve a smooth finish and a uniform dimensions along the length of the timber joist. This can impact the finished size of the product by a few millimetres. The most common types of regularised timber joists are C16 and C24.

Kiln-dried refers to a process where timber or wood is placed inside a kiln to remove excess moisture from it. The controlled heat and airflow in the kiln facilitate faster and more uniform drying compared to air-drying methods. This process reduces the moisture content of the wood, making it lighter, stronger, less prone to warping or cracking, and more stable for various applications in construction, woodworking, or furniture making.

Our pressure treated 4x3 regularised timber joists are available in both a 3.6m and 4.8m length. We do our best to keep these sizes available for delivery, but occasionally, you may receive a longer length as a substitute if stock is delayed or unavailable in your area. 

UK regularised timber is commonly categorised into two grades: C16 or C24. The "C" specifies the wood type: Conifer. The numerical value denotes the bend strength (determined by factors like imperfections and knots) C24 is the stronger grade of the two.

Typically, C16 timber joists are used in wall and roofing applications, while C24 is favoured for situations requiring exceptional strength, notably in roofing and flooring joists.