OSB

OSB, or oriented strand board, is an engineered wood panel built from many thin timber strands laid in cross-oriented layers and bonded under heat and pressure with a waterproof resin. The crossed layers give it strength and stability across the whole sheet, much like plywood, at a keener price, which is why it is widely used for structural sheathing, flooring underlay and wall bracing.

Both are engineered structural panels. Plywood is built from thin timber veneers cross-laminated in layers, while OSB is made from compressed wood strands laid in oriented layers. OSB tends to be more consistent sheet to sheet and lower in cost; plywood is a little lighter and holds edge fixings slightly better. Both handle sheathing, bracing and flooring when they are rated for it, so choose to the specification for the job.

OSB is graded from OSB1 to OSB4 by strength and moisture resistance. OSB2 is a load-bearing grade for dry conditions, which is what our H2 treated wall bracing uses. OSB3 is the load-bearing grade made with a moisture resistant bond for humid conditions, which is what our unsanded sheathing uses. Both are structural.

Yes. Our OSB2 wall bracing is a structural grade, fixed to the relevant bracing specification. The sheets are 6mm and H2 treated for protection against insect attack in dry interior use.

We carry OSB3 sheathing in 2500 × 1250 in 9, 12 and 18mm, and H2 treated OSB bracing in 6mm across 2440, 2745 and 3050 sheet heights. The full range is listed above, and Allmat can order in sizes not held.