Carcassing timber

Frequently asked questions

What strength classes are available for construction timber?
Structural timber is graded into different strength classes such as C14, C24, and C30. C24 is the most common and is used for the majority of construction projects.
When is C24 used compared to C14?
C24 is used for load-bearing structures such as beams and joists in floor systems. It is stronger and more durable, making it suitable for constructions that need to withstand higher loads. C14 is typically used for wall studs in load-bearing interior and exterior walls where the requirements for deformation are not as high.
What is the difference between untreated and treated carcassing?
Untreated carcassing is natural and used indoors or in protected environments. Treated carcassing is treated to resist moisture and rot, making it suitable for outdoor use.
How do I store timber correctly to prevent damage?
Protect from Moisture: Store the timber in a dry place, protected from rain and ground moisture. Use pallets or similar supports to keep the wood off the ground. Ventilation: Ensure that air can circulate around the timber. This helps prevent mould and rot. Protect from Sunlight: Avoid direct sunlight, as it can cause cracking and warping. Covering: Use a tarpaulin or other protective covering, but make sure there is space for the air to circulate. Regular Inspection: Check the wood regularly to ensure it hasn’t been damaged or exposed to moisture.
How do I choose the right sizetimber?
The size you need depends on what you’re building. Common dimensions are 45 x 95 mm and 45 x 145 mm. For load-bearing structures such as roof trusses, C30 may be necessary. Contact customer service for assistance.
Where can I buy Södra’s products?
Södra’s products are available at many building supply stores and retailers. To find the right stockist, we recommend that you: Visit your local building supplier – they often carry our products in stock or can order them for you. Contact our customer service – they’ll be happy to help find a store near you.

For contruction - Standard BS8417

C24

Södra is a leading supplier of high-quality, structural C24 carcassing timber – available in lengths from 2.4 to 7.2 m. Our C24 carcassing timber can withstand the most demanding requirements and outperforms C16 timber for many applications. Denser, more durable and less prone to twisting or bowing, it’s perfect for construction and joinery applications.

We carry extensive stocks of both untreated and treated carcassing across our terminal operations.

We have high-pressure and low-pressure preservative treatment facilities at both New Holland and Sheerness along with low-pressure facilities at Dundee and Wicklow enabling us to treat to your requirements upon request.

Product sheet

Features & Benefits

High-Performance Timber You Can Trust

C24 carcassing timber from Södra offers superior strength, stability, and durability for demanding structural and joinery applications. Denser and more resilient than C16, it’s kiln-dried, sustainably sourced, and available in a wide range of lengths – making it the smart choice for high-performance building projects.

Strength graded to BSEN 14081 – reliable structural performance

Kiln dried – lighter, stronger, and resistant to decay

PEFC certified – sustainably sourced with full chain-of-custody

Nationwide delivery – fast and easy access across the country

maximum durability

UC4 treated deck joists

UC4 treated deck joists are pressure-treated timber beams specifically designed to withstand ground contact and prolonged exposure to moisture. Classified under Use Class 4 (UC4), they are suitable for outdoor applications where the wood is in constant contact with wet conditions—such as the structural framework of decking.

These joists are often incised (cut with small slits) to allow deeper penetration of the preservative, extending their lifespan without compromising strength. They are typically made from kiln-dried C16 or C24 graded timber, treated for maximum durability.