7th Dec 2022 -

4x2 timber is the most recognised size available and is used for both construction and personal projects across the UK. In this overview from Building Materials Nationwide, we’ll explain how timber sizing works within the UK, the different types of 4x2 timber that will be available to buy, and some of the many ways it can be used.

How Would a 4x2 Timber Beam be Sold in the UK?

Within the UK, historically used imperial measurements are not allowed on products. This means that metric measurements, typically millimetres, will be used on all timber sold. The closest equivalent to a 4x2 timber beam will be 100mm x 50mm (this is actually about 3.94 inches by 1.97 inches), so while the term 4x2 may still be used informally, it will be marked in metric sizes when sold.

What Size Will a 4x2 Timber Beam Actually be?

Due to a couple of factors, the timber lengths you buy will not usually be the size specified. Felled trees will be rough-sawned to the exact size specified but this product, known as green wood, will rarely be used or sold. Green wood contains high levels of water, drying and shrinking over time. While there are some uses for green wood within fine detailing, for most construction purposes you will be looking for wood that has been kiln-dried. The drying process will shrink the wood, taking its moisture level to below 20%, meaning it will no longer be the specified size. Another finishing technique on timber that will reduce its size is planing. Planing is essentially sanding, levelling one or more surfaces of timber to ensure a smooth finish. Planed timber will be necessary for many building applications, and will further reduce the size of the wood. Taking these factors into account, a wood that is initially cut to a nominal size of 100mm x 50mm will actually be about 89mm x 38mm when purchased as a timber beam.

What Length Will 4x2 Timber be?

You’ll be able to buy sawn 4x2 timber in a variety of lengths, allowing you to select beams according to your needs. Building Materials Nationwide stocks 4x2 timber in standardised sizes, with our treated timber for instance coming in 2.4m, 3m, 3.6m, 4.2m, and 4.8m.

What Types of 4x2 Timber Are Sold?

Within the UK you will have a range of options available when shopping for 4x2 timber, each of which is suitable for various building and construction applications:

  • CLS 4x2 Timber: CLS timber stands for Canadian Lumber Standard and is defined by meeting a series of visual and strength standards. CLS 2x4 timber will be strength tested and planed on all sides, with curved corners. While it was originally imported from Canada, contemporary CLS timber will likely be from Scandinavian countries.
  • Planed Square Edge 4x2 Timber: Planed square edge timber is a timber that has been kiln-dried, before being planed on each surface. While timber that has only been planed on one or two faces is sometimes available, planed square edge is the most popular type sold in the UK. Planing means that timber can be used in visible applications, as it gives it an attractive and clean look. It also means that wood can be touched without the risk of splinters. Unlike CLS, PSE timber will not necessarily be strength graded, and will have pointed rather than rounded edges.
  • Treated 2x4 Timber: Conventional 4x2 timber made of softwood can encounter a series of issues when installed outdoors, from rot and decay to insect infestation. Pressure-treated timber, sometimes called tanalised timber, has been treated with preservatives designed to offer both water and insect resistance. When looking to use 2x4 timber within an outdoor space or a space at risk from moisture or wood-boring insects, opting for a pressure-treated option is essential.
  • Structural 4x2 Timber (C24): When looking to use 4x2 timber for any sort of load-bearing structural work, you must use wood that is sufficiently tested to ensure its strength. Within the UK, a softwood that has been rated for structural work will usually be sold as either C16 or C24 wood, with C24 being the stronger option. To be rated as a C24 strength grade, 4x2 timber beams will undergo a mechanical test for strength and durability, ensuring that they can support the stress required as part of structural framing. Structural timber will be dried but can be sold rough-sawn as it will not be visible within a finished building.

Need Quality 4x2 Timber?


    • Ideal for wall partitioning and studwork
    • Kiln dried for extra stability

    • Ideal for general construction, fencing, garden and leisure timber applications
    • Pressure-treated
    Price from: £4.18 £5.02

    • Ideal for general construction, fencing, garden and leisure timber applications
    • Pressure-treated
    Price from: £4.18 £5.02

View All Timber

What is 4x2 Timber Used For?

Within both commercial and personal building projects, 4x2 timber is the most popular size of timber beam, owing to its strength and versatility. Here are just some of the popular uses of 4x2 timber:

Wooden Framed Buildings

Structural 4x2 timber will offer a good level of strength, and can be used within the framing and construction of a wooden building. While in all but the smallest buildings stronger timber such as 2x6 or 2x8 timber will probably be needed for the vital structural components, 2x4 beams can be used throughout the framing – particularly when it comes to building interior walls. When looking for the perfect timber to use within framing and construction, ensure you buy boards with an appropriate strength rating, such as C24, as many other options will not guarantee any specific level of strength.

Joists for Decking

4x2 timber’s level of strength is perfect for a variety of external uses, including shed construction and as joists for decking. When looking for the perfect timber joists remember the importance of choosing a treated model for external use. Treated timber joists, or tanalised depending on the seller, will resist the moisture from both rain and soil, allowing a strong foundation for your decking to be fitted over.

Solid Furniture

4x2 timber can also be used for a variety of furniture construction. When looking to build a solid wardrobe, a chest of drawers, a coffee table or more, a planed 4x2 timber will give a beautiful look and a sturdy build. It’s important to opt for a planed model, to avoid the risk of splintering from your furniture.

Our Range of Sturdy 4x2 Timber For Sale

Building Materials Nationwide offers a range of 4x2 timber for sale through our website. We stock CLS timbertreated timber for exterior uses, alongside PSE timber. We work with clients throughout the building industry, offering a full range of building supplies delivered across the UK – all at great prices. To take full advantage of our services, sign up for a trade account through our website today. Our trade account holders get their own dedicated account manager, who’ll help with any large or specific orders you may have. You’ll also be able to take advantage of our huge network of suppliers and our express delivery options.