7th Dec 2022 -

3x1 timber is used for a variety of building tasks, with a range of finishes that can make it suited to exterior use or structural installations. In this guide from Building Materials Nationwide, we’ll explore the precise size of 3x1 timber, the finishes available, and its uses within construction.

How is 3x1 Timber Sold in the UK?

Within the UK, products such as timber can no longer be sold in imperial sizing. While measurements like 3x1 continue to be used informally, all sold timber will be marked in mm. The closest equivalent to a 3x1 timber beam will be a 75mm x 25mm beam. While this isn’t precisely equivalent (3 by 1 inch translates to 76.2mm by 25.4mm) this will be the size offered within the UK. However, due to the size lost during drying and planing, timber sold in the UK will normally be smaller than these stated sizes.

What is the Actual Size of 3x1 Timber?

After a tree is felled, it will be processed within a sawmill into boards of the exact specified dimensions. However, these boards will be rough-sawn and “green” – a term for newly cut trees which indicates a high level of moisture. For them to be used in most construction projects, they will need to be at the very least dried. Kiln drying will lower the moisture level to below 20%, shrinking the beam in the process. For wood that is visible within a project, planing will also be needed. Planing, essentially sanding to create a smooth surface, will also decrease the size of the beams. Because of these factors, a 3x1 timber beam in the UK will be around 64mm x 19mm.

timber stud

How is 3x1 Timber Sold in the UK

3x1 timber can be finished in a variety of ways, with different finishes intended for different purposes within construction and building. The lengths of 3x1 timber will vary, though they’re usually offered in increasing increments of 30cm or 60cm.

  • PSE 3x1 Timber: Planed square edge timber will have a smooth finish on all sides, allowing it to be used for a wide variety of visible uses. Rough-sawn wood will at once look worse, and will also risk causing splinters when used within a building. 
  • Treated 3x1 Timber: Tanalised timber will be treated with preservatives, giving resistance against both water and insects. Softwood timber that is untreated risks decay or rot when it comes into contact with water, with pressure treatment necessary to be used within exterior locations. Wood burrowing insects also present a threat to untreated timber, causing both structural and aesthetic damage.
  • C16 3x1 Timber: C16 timber is graded through a series of tests, ensuring it meets a set level of strength and durability. C16 timber, or C24 timber for even greater strength, can be used within structural work such as framing. This timber is certified as load-bearing, with dependable strength for many years.

Need High-Quality Timber?


    • 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: £2.27 £2.72

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What is 3x1 Timber Used For?

There are a variety of popular uses for 3x1, with its versatile nature making it suited for many construction projects:

  • Fencing: 3x1 timber beams are great for use as fencing boards. For external use, make sure to use tanalised timber, which is suitable for both rainfall and moisture in the soil.
  • Interior Construction: C16 3x1 timber beams can be used for many internal jobs, from furniture building to edging. While still quite a thin option, 3x1 timber can be relied upon for a solid level of strength.
  • Exterior Construction: Planed and treated 3x1 timber can be used within exterior constructions like furniture, shed walls, and edging. This can bring a fetching natural look to your outdoor spaces.

Our Range of Quality Timber

Building Materials Nationwide stocks a wide selection of timber beams. We stock CLS timberPSE timberstructural timber, and treated timber, including 3x1 planed square edge timber, and it’s all sold at competitive prices. We work with customers throughout the trades, offering trade accounts through our website. Our trade account holders get access to their own dedicated account manager, the ability to source products from our wide network of suppliers, and lightning-fast UK delivery options. Sign up for a trade account today, or tell us what you need through the form below.

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