OSB board and OSB3 sheets
OSB board is a structural sheet material used for roof decking, shed roofs, flooring, loft boarding, wall lining, outbuildings and general building work. OSB3 is designed for structural use in humid conditions, which is why it is the common choice for many building and roofing jobs. It is moisture resistant rather than waterproof, so exposed boards still need suitable protection.
Which OSB board do you need?
| OSB board | Typical uses |
|---|
| 9mm OSB3 | Lightweight boarding, lining, boxing-in and general sheet work where suitable support is provided. |
| 11mm OSB3 | Shed roofs, garden buildings and roof decking where the structure is properly supported and covered. |
| 18mm OSB3 | Floors, loft boarding, stronger roof decks, storage decks and jobs needing a stiffer board. |
| 18mm OSB3 Tongue & Groove | Flooring, loft boarding and decked areas where an interlocking edge helps support the joint. |
OSB3 for roofing and shed roofs
OSB3 is widely used as the deck under felt, roofing membrane or EPDM. 11mm OSB3 is a common option for suitably supported shed roofs. 18mm OSB3 gives a stiffer deck for heavier-duty roof and floor applications. For roof coverings, browse Roofing Membrane & Shed Felt or EPDM Rubber Roofing.
OSB3 for flooring and loft boarding
18mm OSB3 is commonly chosen for flooring, storage decks and loft boarding. Support square-edge board joints properly. If you want interlocking edges between sheets, choose 18mm OSB3 Tongue & Groove Board.
OSB or plywood?
Choose OSB3 when you need a practical structural board for hidden or covered work. Choose plywood sheets when face quality, grade choice, finish or a specific plywood specification matters. For a fuller comparison, read OSB vs Plywood.
More OSB guidance
Compare all Sheet Materials, or use Which Sheet Material Should I Use? for a broader guide.
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