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8x3 Timber Treated (3 Products)

Stress-graded to C24, this 8x3 treated timber is one of the highest quality types of timber available for structural applications such as flooring joists, roofing, as well as timber frame stud walls. When put up against other materials, such as C16-graded timber, it prevails with less knots and fewer physical flaws. Our vast range of 8x3 sawn timber is sawn to length and pressure-treated with chemicals to ensure ultimate protection against fungal attacks and insects.

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8x3 Timber Treated

What Is 8x3 Timber Used For?

8x3 carcassing timber can be applied both internally and externally and is a premium material choice for floor joists, roof joists, loft conversions and timber framing construction.

8x3 timber is also highly versatile in the sense that it is suitable for general construction, as well as a range of garden projects. 

8x3 carcassing timber performs best in the following applications: 

  • Stud walls
  • Joists - roofs, floors and decking
  • Structural and general joinery applications
  • Timber framing construction


We stock 8x3 timber in lengths of 3.6m, 4.8m and 6m- these are also available in packs of 35. We also stock a range of accessories (such as wood screws) to help you get your project underway. 


Should you require a different size, we stock a wide range of sizes and lengths of timber related products to accommodate your project needs. 

For all other building materials (from decorative aggregates to concrete blocks) check out our many categories to find the best solution for your next project. 

8x3 Timber Specifications

  • Graded to a superior C24 standard - excellent tensile strength
  • Regularised with an eased edge - comfortable handling
  • High-density
  • Finished size: 195 mm x 70 mm ( 8″ x 3″)
  • Pressure treated with Tanalith 'E' - helps to prevent rot and protect from moisture 
  • Kiln dried for extra stability 
  • FSC Certified - responsibly sourced 

Please note: timber is a natural product that may vary in colour, visual details, knots, grain, and texture.

What Does C24 Grade Mean?

At Materials Market, we only sell the highest quality C24-graded 8x3 timber. But what does C24 mean exactly?

C24 grade is the superior cousin of C16 and offers a stronger, more robust product than lower-graded timbers as it comprises considerably fewer knots. This renders it compatible with structural applications that require durability and sturdiness, such as floor joists or roof battens.

C24 timber is particularly ideal for bearing heavier loads and spanning wider areas than lower-graded timbers. This high-quality timber can only be sourced from regions where the climate produces a slower growth rate (and tighter grain).

Why Choose Treated Timber? 

Simply put, untreated timber is as it sounds; it is not treated with preservatives or chemicals. This makes it a more "natural" solution. Treated timber, on the other hand, is treated with chemicals and preservatives to make it last longer and provide it with additional protection from rot, wear, and pests.

Here are just a handful of the benefits on offer with treated timber:  

  • It is treated to resist rot, decay and insect attacks
  • The most durable timber option which offers extra stability, making it ideal for outdoor use
  • Thanks to its treated nature, treated timber is also low-maintenance
  • You won't have to spend time and money regularly maintaining it

What Does Pressure Treated Mean? 

Pressure-treated wood goes through a process chemical infusion process to create a more durable and long-lasting product. 

It's imperative to remember that while this type of treatment helps prevent rot and insects, weathering and corrosion are still possible over time.

Frequently Asked 8x3 Questions

How Is 8x3 Timber Sized On Materials Market? 

Here at Materials Market, we list timber sizes in a couple of different ways. Timber lengths are usually referred to in imperial terms (inches rather than millimetres) and are characterised by their width and height. The most popular way we refer to size is in inches like '8 x 3' but we also use metric, which measures in millimeters (mm). 

For 8 x 3 timber this would be 200mm x 75mm or 72mm x 200mm. We sell 75mm x 200mm on this website and this is used interchangeably with 8 x 3 to refer to the same size of product. The slight discrepancy of 3mm between 47mm (finished size) and 50mm (nominal size) just means that the finish at the ends is a lot more even and easier to work with.

Whatever your project, our site is proud to present a wide range of standard sizes for easy fitting; offering timber products that will be of interest to both new and seasoned builders. 

Is It Possible To Paint 8x3 Timber C24?

Pressure-treated wood can be painted or stained, but to get a finish that lasts and looks premium, you'll first need to evaluate the moisture content of the timber.


Once you are sure the timber is dry, you can then move on to using a suitable primer and paint finish. We recommend using a latex primer with compatible exterior latex paint—water-based paint. Oil-based paints are not recommended.

Am I Able To Cut Treated Timber To My Preferred Size?

Yes, it is possible to cut treated timber, provided that you have all the appropriate power tools, eye protection, and a respirator to hand before cracking on. Donning the correct PPE is essential as the cutting process releases tiny airborne particles of wood, possibly impregnated with the chemicals used in pressure-treating.

Treated wood also cuts a little more like wet wood so some extra care should be afforded to ensure the blade doesn’t slip while cutting. 

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