Graded timber

Innovation that enables striking designs.

Whether for its aesthetics or its environmentally friendly qualities, architects, engineers, and designers are increasingly turning to timber as the primary material in their projects, in recognition of its sustainability, warmth, and natural beauty.

We produce premium C24 and C27 British graded softwood structural timber that can bear the heaviest loads and with wider beams to span larger distances, enabling the construction of more complex and ambitious structures. 

From our state-of-the-art facility, we produce graded timbers that are certified for use in domestic and commercial construction, supplying the optimal timber to meet the needs of your project that can be crafted to any specification.

Technical specification

Product specification

Structural Softwood Graded Timbers

Strength Class

Bending Strength (f_m,k)

Mean Stiffness (Em,0,mean)

Common Applications

C16

16N/mm2

8kN/mm2

Internal stud walls, short-span floor joists, and rafters.

C18

18N/mm2

9kN/mm2

Mid-strength joists and small roof trusses.

C22

22N/mm2

10kN/mm2

High-load rafters and joists; typically specified by engineers to save on timber depth vs C16.

C24

24N/mm2

11kN/mm2

Premium standard for long-span floor joists, flat roofs, and balconies.

Key specification differences
  • Availability: C18 is sometimes sold interchangeably with C16 in the UK (often stamped C16/C18) depending on the source. C22 is rarer and usually requires a specialist order or is machine-graded for specific large-scale projects.
  • Stiffness vs. strength: C22 offers significantly higher stiffness than C18 (10 vs 9kN/mm²), which is critical for reducing "bounce" in floor systems.
  • Grading stamp: Every piece must be clearly stamped with its specific class (C18, C22, etc.) to comply with BS EN 14081-1. If you resaw a C22 board lengthwise, its strength grade is no longer applicable, and it must be re-graded.

Strength classes

(C16 - C24 for softwoods) and compliance with BS EN 14081-1. Below is an example of a technical specification for standard structural carcass timber used in the UK.

Technical Specification: Structural graded softwood (C24)

CategorySpecification DetailsStandards & Compliance
Strength classC24 (coniferous/softwood)BS EN 338 / BS EN 1912
Grading methodMachine strength graded or visual (SS grade)BS EN 14081 / BS 4978
Moisture contentKiln dried (KD) to < 20%BS EN 13183-2
Bending strength24 N/mm² (characteristic)BS EN 338
Surface finishRegularised (planed all round) with eased edgesIndustry standard
Dimensional tol.+/- 1mm thickness; +/- 2mm widthBS EN 336 (class T1/W1)
PreservationPressure treated (e.g., Tanalith E)BS 8417 (use class 1 or 2)
SustainabilityFSCChain of custody required
IdentificationGrade stamp must be visible on every pieceBS EN 14081-1
Key construction grades explained
  • C16: A more economical grade suitable for general framing, internal stud walls, and short spans where higher load bearing is not critical.
  • C24: The premium construction grade, offering higher strength and fewer knots. It is the industry standard for floor joists, roof rafters, and longer spans.
  • Regularised: Timber that has been planed to a consistent size (e.g., a "47mm" board finishing at roughly 45mm) to ensure all joists in a run are identical in height.

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