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. C14 is typically used for wall studs in load-bearing interior and exterior walls | |
| What is the difference between untreated and treated timber? | |
Untreated timber is natural and used indoors or in protected environments. Treated timber is treated to resist moisture and rot, making it suitable for outdoor use. | |
| How do I store timber correctly to prevent damage? | |
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| 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:
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Untreated Carcassing
Discover our untreated construction timber, made from high-quality wood for maximum durability and strength. We offer timber that can be customised to suit your needs for both indoor and outdoor projects.
Treated Carcassing
Our treated construction timber is low maintenance and offers high resistance to wood-destroying organisms. With extended lifespan and quality-assured NTR classifications, it’s perfect for fences, decking, and other outdoor structures.
reliability and versatility
CLS Timber
CLS timber refers to wood that meets the Canadian Lumber Standard. It is a softwood that has been planed and rounded on all sides, resulting in a smooth and even surface. Originally from Canada, CLS timber is valued for its high quality, consistent dimensions, and wide range of uses. It is typically made from spruce, pine, or fir – collectively known as SPF (Spruce-Pine-Fir).
Thanks to its reliability and versatility, CLS timber is suitable for many types of projects. It’s commonly used in new constructions, extensions, structural framing, as well as for building custom furniture and various DIY projects.
Structural timber
TR26
Södra has a long history of supplying machine strength graded TR26 softwood to roof truss and metal web joist manufacturers and stock an extensive range of high quality TR26 graded timber to meet the needs of our customers. TR26 is a machine strength-graded structural timber, commonly used in the construction industry for:
- Roof trusses (trussed rafters)
- Flanges in open web joists (e.g. Posi-Joists)
- Metal web beams
Features and Benefits
Strength You Can Build On
TR26 is the go-to choice for structural solutions that demand strength, precision, and sustainability. With consistent quality and reliable performance, our TR26 graded softwood delivers key benefits that make a real difference in both manufacturing and final construction.
Available in long lengths – reduces splicing, plate costs, and handling
Finger jointed for stability – ensures straighter metal-web joists
Low moisture content – minimizes movement and improves dimensional accuracy
Quality assured – manufactured to EN15497:2014 standards
Sustainably sourced
Glulam
Glulam beams are strong, laminated timber elements ideal for long spans, roof structures, and columns. They offer high load capacity, dimensional stability, and can be shaped straight or curved.
Rim boards are used in floor and roof framing to support joists and transfer loads. Made from LVL, OSB, or plywood, they prevent rotation and improve structural integrity.
Both are sustainably sourced and essential for durable, high-performance timber construction.
solid softwood
KVH
KVH Structural Timber is a building material from Germany with precisely defined product characteristics which have been developed especially to meet the requirements of modern timber construction. KVH is a kiln-dried finger-jointed product made of solid softwood and is strength-graded.
Features andBbenefits
Build Better with KVH
Engineered for precision and built to perform – KVH Structural Timber combines German quality with modern construction demands. Its long lengths, dimensional stability, and certified sustainability make it a smart choice for efficient, high-quality building solutions.
Available in long lengths – reduces splicing, handling, and overall material costs
Finger jointed for stability – ensures straighter joists and consistent performance
Quality assured – manufactured to EN15497:2014 standards
Certified sustainability – full PEFC Chain of Custody
highly stable
Laminated Veneer Lumber
Laminated Veneer Lumber (LVL) is a strong, engineered wood product made by gluing thin layers of veneer with the grain in the same direction. It’s highly stable and ideal for beams, joists, studs, and trusses.
LVL offers excellent strength-to-weight ratio, resists warping, and is made from sustainably sourced wood—making it a reliable and eco-friendly choice for structural use.
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.
For contruction
C24
Södra is a leading supplier of high-quality, structural C24 carcassing timber – available in lengths from 2.4m to 6m. 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.
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
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