UK Plywood & OSB Grades Reference
Structural plywood and OSB grades, thicknesses, moisture classes and applications for UK construction projects.
OSB Grades (BS EN 300)
| Grade | Type | Conditions | Typical Use |
|---|---|---|---|
| OSB/1 | Non-structural | Dry only | Packaging, interior linings |
| OSB/2 | Structural | Dry only | Structural panels in dry locations |
| OSB/3 | Structural | Humid | Sheathing, flooring, flat roofs |
| OSB/4 | Heavy-duty structural | Humid | High-load floors, structural diaphragms |
Common OSB Thicknesses
| Thickness (mm) | Sheet Size (mm) | Edge Type | Common Use |
|---|---|---|---|
| 9 | 2440 x 1220 | Square edge | Wall sheathing, sarking |
| 11 | 2440 x 1220 | Square edge | Wall sheathing, racking |
| 15 | 2440 x 1220 | Square / T&G | Roof decking, light floors |
| 18 | 2440 x 1220 / 2440 x 600 | T&G | Floor decking (400 mm centres) |
| 22 | 2440 x 600 | T&G | Floor decking (600 mm centres) |
| 25 | 2440 x 1220 / 2440 x 600 | T&G | Heavy-duty floors, flat roofs |
Structural Plywood Grades (BS EN 636)
| Class | Service Class | Conditions | Bonding |
|---|---|---|---|
| EN 636-1 | SC1 (dry) | Interior, heated buildings | Type I (interior) |
| EN 636-2 | SC2 (humid) | Covered but unheated, risk of wetting | Type II (moisture resistant) |
| EN 636-3 | SC3 (exterior) | Fully exposed external | Type III (weather/boil proof) |
Common Plywood Thicknesses
| Thickness (mm) | Typical Use |
|---|---|
| 3.6 | Drawer bottoms, backing panels |
| 5.5 | Panelling, templates |
| 9 | Wall sheathing, soffit boards |
| 12 | Shelving, sheathing, shuttering |
| 15 | Roof decking, shelving |
| 18 | Flooring, worktops, furniture |
| 22 | Heavy flooring, structural |
| 25 | Heavy structural, formwork |
Related Calculators
Use the UK Timber Sizes reference for structural timber, or the MDF & Chipboard Sizes for non-structural sheet materials.
How We Calculate This
Frequently Asked Questions
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Last updated: April 2026
All calculations are estimates. Verify with your supplier.