5x2 Treated Timber C24 Regularised Sawn Joist 47x125mm – 3.6m

Typically measured in inches, “5x2” refers to the size of the joist in inches which is 47x125mm in mm. However, the true size of 5x2 Timber in mm is slightly smaller, due to the fact that most of our structural timber is regularised, which involves machining a length down to a uniform width and thickness along the entire length. This means that the “finished” size can be a few mm smaller than 47x125mm, usually closer to 45mm x 120mm.

This slight difference is minimal and in the vast majority of projects will make no material difference to your project, and is typical when using 5x2 regularised timber joists.

Though a less common size than our 4x2 Timber, 5x2 Timber has the benefits of a larger size, and when graded to C24 means it is a strong and sturdy timber ideal for use in roofing and flooring, as well as providing a sturdy base in decking frames. For outdoor use, it is advised to treat the timber for protection against moisture and pest damage. 

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 5x2 Timber joists are available in 2.4m, 3m, 3.6m, and 4.8m. We try to keep all of these lengths in stock wherever possible, but on occasions where stock levels or availability in your area is low, we may substitute for a longer length.

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.

It is advisable to opt for our treated 5x2 Timber Joists for any uses where they are likely to come into contact with moisture or pests.