The Story
C24 graded structural timber at 47mm x 225mm is a heavy-section, kiln-dried softwood regularised for consistent sizing, making it the go-to choice for long-span floor joists, roof rafters, and major structural framing where load-bearing performance is critical.
Specifications
| Material | Structural softwood |
| Grade | C24 strength graded |
| Finish | Sawn, regularised, eased edges |
| Nominal Size | 47mm x 225mm |
| Finished Size | Approximately 45mm x 220mm |
| Moisture Content | Kiln dried to 20% or below |
| Length(s) | 3.6m, 4.8m, 6.0m |
| Profile | Rectangular, eased arris |
What it's used for
- Floor joists in new-build and renovation projects where span and load ratings demand a full 225mm depth
- Roof rafters and purlins for pitched roofs, loft conversions, and room-in-roof structures
- Structural beams and headers above wide openings in timber-frame construction
- Engineered decking subframes and commercial structural applications where graded timber is specified by a structural engineer
Fitting and handling
Store this timber flat and off the ground, fully supported along its length, in a dry covered area before installation to prevent bowing or moisture uptake. Although kiln dried to 20% or below, allow a short acclimatisation period on site before fixing, particularly in heated buildings. Fix using structural joist hangers, M12 bolts, or ring-shank nails as specified in your structural drawings, and ensure all end-grain cuts on site are treated with a suitable end-grain preservative sealant before enclosing.
FAQ
What is the difference between C16 and C24 structural timber?
C24 has a higher bending strength, stiffness, and density rating than C16. For a 47mm x 225mm section, C24 allows longer joist spans and higher load capacities, which is why structural engineers often specify it for floors, roofs, and beams where C16 would need a larger section or closer centres to achieve the same performance.
Is this timber suitable for floor joists in a loft conversion?
Yes. The 47mm x 225mm C24 section is widely used for loft conversion floor joists because the 225mm depth provides the span and load capacity typically required, and the C24 grade satisfies Building Regulations Part A structural requirements. Always confirm joist centres and spans with your structural engineer or approved inspector.
Does Nottage Timber Merchants offer a cut-to-length service for this size?
Yes. Nottage Timber Merchants can cut structural timber to your required lengths. Contact us directly with your cutting list and quantities for a trade price. Stock lengths of 3.6m, 4.8m, and 6.0m are available for immediate despatch or collection from our Bridgend yard.
Browse the full range of C24 graded timber at Nottage Timber Merchants. We supply trade and self-build customers across Bridgend and South Wales, with next-day delivery available to most local postcodes on stocked sections.
Description
C24 graded structural timber at 47mm x 225mm is a heavy-section, kiln-dried softwood regularised for consistent sizing, making it the go-to choice for long-span floor joists, roof rafters, and major structural framing where load-bearing performance is critical.
Specifications
| Material | Structural softwood |
| Grade | C24 strength graded |
| Finish | Sawn, regularised, eased edges |
| Nominal Size | 47mm x 225mm |
| Finished Size | Approximately 45mm x 220mm |
| Moisture Content | Kiln dried to 20% or below |
| Length(s) | 3.6m, 4.8m, 6.0m |
| Profile | Rectangular, eased arris |
What it's used for
- Floor joists in new-build and renovation projects where span and load ratings demand a full 225mm depth
- Roof rafters and purlins for pitched roofs, loft conversions, and room-in-roof structures
- Structural beams and headers above wide openings in timber-frame construction
- Engineered decking subframes and commercial structural applications where graded timber is specified by a structural engineer
Fitting and handling
Store this timber flat and off the ground, fully supported along its length, in a dry covered area before installation to prevent bowing or moisture uptake. Although kiln dried to 20% or below, allow a short acclimatisation period on site before fixing, particularly in heated buildings. Fix using structural joist hangers, M12 bolts, or ring-shank nails as specified in your structural drawings, and ensure all end-grain cuts on site are treated with a suitable end-grain preservative sealant before enclosing.
FAQ
What is the difference between C16 and C24 structural timber?
C24 has a higher bending strength, stiffness, and density rating than C16. For a 47mm x 225mm section, C24 allows longer joist spans and higher load capacities, which is why structural engineers often specify it for floors, roofs, and beams where C16 would need a larger section or closer centres to achieve the same performance.
Is this timber suitable for floor joists in a loft conversion?
Yes. The 47mm x 225mm C24 section is widely used for loft conversion floor joists because the 225mm depth provides the span and load capacity typically required, and the C24 grade satisfies Building Regulations Part A structural requirements. Always confirm joist centres and spans with your structural engineer or approved inspector.
Does Nottage Timber Merchants offer a cut-to-length service for this size?
Yes. Nottage Timber Merchants can cut structural timber to your required lengths. Contact us directly with your cutting list and quantities for a trade price. Stock lengths of 3.6m, 4.8m, and 6.0m are available for immediate despatch or collection from our Bridgend yard.
Browse the full range of C24 graded timber at Nottage Timber Merchants. We supply trade and self-build customers across Bridgend and South Wales, with next-day delivery available to most local postcodes on stocked sections.
