How and where to use guide
2.4Mtr X 47 X 75mm Treated Regularised KD Carcassing Timber
Typical applications
This timber size is commonly used for floor joists in domestic and light commercial construction, roof battens and purlins, stud wall framing, and decking frame construction. The C24 grade provides the load-bearing capacity needed for these structural roles, whilst the treated finish extends service life in exposed conditions. It is equally suitable for internal applications where moisture control is important, such as bathrooms and kitchens.
- Floor joists in domestic and light commercial buildings
- Roof battens, purlins, and structural roof work
- Stud wall framing for partition and external walls
- Decking frame and joist construction
- Internal structural work in moisture-prone areas
Structural design and loading
C24 timber has defined strength properties that allow it to be used in structural calculations and design. Consult building regulations and relevant design standards (BS EN 1995-1-1 Eurocode 5) to confirm that the 47 × 75 mm section is adequate for your specific span and loading conditions. For floor joists, typical spans depend on load class and joist spacing; roof applications will vary based on pitch and snow load. Always verify your design with a structural engineer or use approved span tables.
- Suitable for structural calculations to Eurocode 5
- Check span tables for floor joists at your intended spacing
- Confirm adequacy for roof loading in your location
- Consult a structural engineer for non-standard applications
Installation and fixing
The regularised finish allows straightforward installation with minimal planing required on site. Fix using appropriate fasteners—typically galvanised or stainless steel nails, screws, or bolts depending on the connection detail. For floor joists, use joist hangers or traditional bearing on walls; for roof work, follow the design specification for rafter ties and connections. Ensure all fixings are corrosion-resistant to complement the treated timber.
- Use galvanised or stainless steel fasteners
- Install joist hangers for floor joist connections where specified
- Follow design details for roof rafter and tie connections
- Ensure adequate bearing length on supporting walls or beams
- Cut and notch carefully to avoid excessive weakening
External and exposed use
The pressure treatment makes this timber suitable for external applications such as decking frames, garden structures, and exposed roof work. However, the treatment is not a substitute for good design practice—ensure adequate ventilation, drainage, and protection from standing water. End grain and cut surfaces are less protected than the original treated faces; consider applying additional preservative to freshly cut ends in exposed locations.
- Suitable for external decking frames and garden structures
- Ensure good ventilation and drainage in external applications
- Protect from standing water and prolonged wet conditions
- Apply additional preservative to freshly cut ends if exposed
- Not suitable for ground contact without additional protection