4x2 Treated Timber C24 Regularised Sawn Joist 47x100mm - 2.4m

4x2 Treated Timber Joists are 47x100mm in size (finished size approx. 45x95mm) and 2.4m in length, made from high quality, responsibly sourced timber from FSC certified forests. Each 4x2 treated timber length is kiln dried for straightness and strength and treated for resistance to moisture and pests. 

• Kiln Dried for additional strength and durability
• FSC Certified Timber
• For use in exterior and structural applications
• Regularised for uniform size, with eased corners
• Graded to C24 strength grade
• Conforms to BS 4978 and EN 14081:2006

What is 4x2 Timber in mm?

Typically measured in inches, “4x2” refers to the size of the joist in inches. However, if you want to know what 4x2 Timber is in mm - the equivalent size is 47 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 47x100mm, usually closer to 45mm 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 47x100, 4x2 regularised timber joists.

What are 4x2 C24 Timber Joists Used For?

4x2 regularised timber joists are the most commonly used size of timber joist. It has many uses, but due to its strength, it is commonly used in the construction of decking and garden buildings, as well as in the walls, roofs and floors of timber-frame buildings.

What is Regularised Timber?

Throughout our website, you will see many timber joists referred to as “regularised” - this means that the length of timber has been machine-finished to achieve a smooth finish and a uniform length and width 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.

What Does Kiln Dried Mean?

Kiln dried timber is made through the process of kiln drying - where cut timber boards are dried in kilns with continuous, even application to remove excess moisture from the fresh timber. This reduces the weight, increases the strength and straightness, and makes it easier to work with. It is also a much faster process than air-drying timber joists, which can take several months to a year. 

What Lengths Do 4x2 C24 Timber Joists Come in?

We offer both treated 4x2 regularised timber joists and untreated in a variety of sizes: from 2.4m, 3m, 3.6m and 4.8m. We do our best to keep all sizes available for delivery, but occasionally, you may receive a longer length as a substitute if stock is delayed or unavailable in your area. 

What Does C24 Stand For?

Regularised timber is commonly graded into one of two grades in the UK - C16 or C24. The “C” refers to the variety of wood used, which in this case is Conifer. The number refers to the strength grading that timbers are sorted into based on a number of factors such as imperfections, knots, etc, with C24 being the stronger of the two.

Most commonly, C16 timber joists are used in many wall and roofing applications, whilst the C24 is used for particularly high-strength requirements such as roofing and flooring joists.

Do I Need Treated 4x2 Timber?

If your project is likely to be exposed to moisture or pests, it is always advised to opt for 4x2 treated timber. They are pressure treated which ensures the treatment is forced into the wood to ensure a longer-lasting treatment and protect wood from rot and pests. Typically, for decking, roofing and other outdoor projects.