UK Timber Sizes — CLS and Regularised Reference
Standard UK timber sizes for structural and non-structural use, including CLS, regularised, sawn, and planed dimensions in metric and imperial.
CLS Timber Sizes
| Finished Size (mm) | Imperial Equivalent | Common Use |
|---|---|---|
| 38 x 63 | 1.5" x 2.5" | Battens, noggins, light framing |
| 38 x 89 | 1.5" x 3.5" | Stud walls (non-load-bearing), partitions |
| 38 x 140 | 1.5" x 5.5" | Load-bearing stud walls, sole plates |
| 38 x 184 | 1.5" x 7.25" | Heavy-duty stud walls, headers |
| 38 x 235 | 1.5" x 9.25" | Deep stud walls, platform frame floors |
| 38 x 286 | 1.5" x 11.25" | Deep floor joists, headers |
Regularised Structural Timber (Joists, Rafters, Studs)
| Nominal Size (mm) | Finished Size (mm) | Common Use |
|---|---|---|
| 47 x 100 | 45 x 95 | Ceiling joists, light rafters |
| 47 x 125 | 45 x 120 | Ceiling joists, flat roof joists |
| 47 x 150 | 45 x 145 | Rafters, floor joists (short spans) |
| 47 x 175 | 45 x 170 | Floor joists, rafters |
| 47 x 200 | 45 x 195 | Floor joists (standard domestic spans) |
| 47 x 225 | 45 x 220 | Floor joists (longer spans), trimming joists |
| 75 x 150 | 73 x 145 | Purlins, heavy floor joists |
| 75 x 200 | 73 x 195 | Purlins, ridge boards, trimmer joists |
| 75 x 225 | 73 x 220 | Large purlins, ridge boards |
Battens and Carcassing
| Sawn Size (mm) | Common Use |
|---|---|
| 25 x 38 | Tile battens (BS 5534) |
| 25 x 50 | Counter battens, plasterboard battens |
| 38 x 50 | Roofing battens (heavy tiles), grounds |
| 47 x 50 | Wall plate, noggings |
| 50 x 50 | Fence post rails, studwork |
Related Calculators
Use the Joist Span Calculator for correct joist sizing, or the Timber Calculator for quantities. The Rafter Calculator helps with roof timber sizing.
How We Calculate This
Frequently Asked Questions
Related Calculators
Concrete Mix Ratios
Standard UK concrete mix ratios explained with quantities per cubic metre and guidance on when to use each.
Insulation U-Values
Part L target U-values for walls, floors, roofs and windows with insulation thicknesses to achieve compliance.
UK Brick Dimensions
Standard UK brick sizes, coordinating dimensions and bricks per square metre for common bond patterns.
UK Cable Sizes
BS 7671 cable sizes and current ratings for common UK domestic circuits and installations.
UK Plasterboard Sizes
All standard UK plasterboard sizes, thicknesses, weights and types including fire-rated and moisture-resistant boards.
Last updated: March 2026
All calculations are estimates. Verify with your supplier.