4x4 Timber (100mm x 100mm): Popular Uses and Types Available

4x4 timber is a sturdy, square-faced beam type that can be used both within building construction and as posts within a garden. In this guide from Building Materials Nationwide, we’ll examine the UK sizes of a 4x4 timber beam, looking at the nominative vs. actual sizing. Then, we’ll look at the various finishes available and the common uses for 4x4 timber in both commercial and DIY construction.

What Size is 4x4 Timber in Metric?

While imperial sizings for timber, such as 4x4, continue to be used throughout much of the world, within the UK metric sizes must be used when selling products. Informally, these sizes persist within the building world. The equivalent of a 4x4 will be a 100mm x 100mm timber beam. 4 inches actually translates to 101.6 mm, so when shopping for timber within the UK you will not be able to exactly order a 4x4 (though, as we’re about to explain, the size of a 4x4 will not actually be 4x4 most of the time anyway).

Nominal Vs. Actual Sizes

When buying timber, the nominal size given (in this case, 4x4) is the size that the wood was sawn to from the felled tree. This is known as green timber, and while it has a few benefits for manufacturing small wooden items, within construction or furniture projects it is not advised for use as it will shrink over time. The majority of 4x4 sawn timber sold will be dried and potentially planed. Both of these processes will result in the timber being smaller than the nominal size. So, instead of being 100mm by 100mm, a 4x4 timber beam in the UK is likely to be about 89mm by 89mm.

What Lengths is 100mm x 100mm Timber Sold in?

The lengths of 100mm x 100mm timber are varied, though standard sizes within the industry usually go up in 30cm or 60cm increments. This means that lengths of 1.2m, 1.5m, 1.8m and more up to around 3m are available for sale.

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What Types of 4x4 Timber Are Available?

4x4 timber can be sold with a range of finishes, each tailored around specific purposes in construction. Depending on your intended usage there may be specific finishes that better suit the job.

4x4 Green Timber

Green timber, sometimes called unseasoned timber, is freshly sawn from felled trees and sold as-is. Unseasoned timber has the benefit of being easy to cut and shape, allowing it to be made into a wide variety of different shapes with minimal resistance. Due to its high moisture content, it will dry over time, naturally shrinking as it does so. Green timber can be used in construction but its shrinkage will need to be taken into account at every stage of planning and building.

4x4 Pressure Treated Timber

Pressure-treated timber will be kiln-dried, reducing the level of moisture within it to below 20%. It will then be treated with preservatives, which will be pressurised so they fill the wood as well as coat its exterior. Treated timber will boast water and insect resistance, making it suitable for external use. Untreated wood can have serious issues with water, such as decay and rot.

4x4 Planed Timber

Planed timber will be planed on one or more sides, giving it a smooth and visually pleasing appearance. When looking for wood that will be visible, planed timber should be used. Using PAR, or planed all round timber, means that all faces will be planed, but in situations where only one or two of the faces will be visible, you may be able to save money by opting for planed single-edge timber (PSE) or a planed both sides timber (PBS). 

What is 4x4 Timber Used For?

4x4 timber will be a larger square post, intended for construction or framing use. Here are some of the applications where 4x4 timber could be used:

• Newel Posts: A wooden newel post will be a feature within a stairwell, offering support for the balusters and handrail. 4x4 timber will make for a suitably sturdy newel post.
• Battening: Within timber buildings battening will be used within the walls, roof, and floor, supporting construction. Stronger 4x4 timber can therefore be installed within timber buildings as battens.
• Fencing or Exterior Use: Due to their large size, 4x4 timber beams can be used as fence posts. This would need to be treated timber to deal with both the water from rain and the moisture within the soil.

Professional Timber Suppliers

Building Materials Nationwide offers a range of timber lengths for sale, which can all be delivered across the UK. We work with clients throughout the building industry, sourcing all needed products with quick delivery turnarounds. Through our website, you can explore our range of timber and joinery, including treated timber, structural timber, and CLS timber. Customers within the industry can also sign up for a trade account through our website. Our trade account holders will be paired with a dedicated account manager, a real person able to organise large or complex orders, and who will also work with our extensive network of suppliers to source products not listed on our website.

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