C24 Grade 47 x 150mm x 4.8m Treated Timber
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Product Details
C24 grade timber is a high-strength structural softwood, typically spruce or pine, that has been kiln-dried and treated to resist rot, insect damage, and decay. The "C24" designation refers to its minimum bending strength of 24 N/mm², making it significantly stronger and more reliable than lower grades like C16, with fewer knots and a tighter grain for superior durability. This 47 x 150mm size (commonly called 6x2) is ideal for demanding DIY projects including floor joists, roof rafters, wall framing, and decking structures where you need to span longer distances or support heavier loads. The treated specification means it's suitable for both internal and external use, though for ground contact applications you should verify it meets the appropriate treatment use class for your specific project. Its kiln-dried finish ensures stability and makes it easier to work with than wet-graded timber, while the regularised (planed) edges provide a cleaner, splinter-free finish perfect for visible structural elements.
As of August 2026, PriceNailer data confirms that the cheapest price for C24 Grade 47 x 150mm x 4.8m Treated Timber is £16.13 from BuildingMaterials.co.uk across 7 suppliers. Prices have decreased by 4.3% over the last 7 months.
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Frequently Asked Questions
What is the actual size of 47 x 150mm C24 treated timber?
The 47 x 150mm dimensions are the finished regularised (planed) sizes, so this timber measures exactly 47mm x 150mm. This is smaller than the sawn size due to the planing process that creates smooth, splinter-free edges.
What joist centres can I use with 47 x 150mm C24 timber for flooring?
For floor joists using 47 x 150mm C24 timber, you can typically span up to 3.6m at 400mm centres or 3.2m at 600mm centres for domestic loads. Always check Building Regulations and structural calculations for your specific application.
Is C24 treated timber suitable for outdoor decking frames?
Yes, C24 treated timber is excellent for decking subframes and structural elements. However, verify the treatment class - Use Class 3 is suitable for above-ground external use, while Use Class 4 is needed for ground contact applications.
What's the difference between C24 and C16 grade timber?
C24 has a minimum bending strength of 24 N/mm² compared to C16's 16 N/mm², making it 50% stronger. C24 also has fewer knots, tighter grain, and can span greater distances or carry heavier loads than C16 timber.
Can I use 47 x 150mm C24 timber for roof rafters?
Yes, this size is commonly used for roof rafters in domestic construction. The high strength of C24 grade makes it ideal for spanning between supports, though you should verify spacing and span requirements with structural calculations or Building Control.