information/FAQs

Storage and fixing of plywood

Plywood should always be stored in a dry shelter protected from sunlight. Panels should be stored flat. Do not lean panels against a wall or the side of the rack for long periods.

No plywood panel will stay entirely flat under all ambient conditions if left free to move. Warping, bowing and twisting can occur due to moisture imbalances, unbalanced laminates or paint coats or unbalanced stresses. It is strongly recommended, therefore, that plywood should always be positively fixed to supports.

Depending on the type of supports, plywood can be fixed with standard fasteners. Full fixing requirements for plywood bracing, flooring, roofing and webbed beams are given in the relevant articles.

Plywood to timber support connections can be made with hand or machine driven nails, or wood screws. In arduous applications or where low joint strength support species such as plantation pines, oregon and spruce pine fir (SPF) are used, deformed shank nails are recommended. Plywood can be nailed close to the edge (within 7mm for plywood up to 7mm thick and 10-12mm for thicker plywood) without fear of splitting.

Self drilling and tapping screws are recommended for plywood to steel fixings. It is often beneficial in applications such as flooring to use a structural elastomeric adhesive as well as mechanical fasteners. Resorcinol adhesives are unsuitable for on-site use as they require high fixing pressure and are very sensitive to curing conditions.

Bending plywood is relatively simple. Plywoods with Type A bond phenolic glue lines can be soaked or steamed to assist bending. It is not possible to obtain a compound curve when bending flat plywood panels. Unsupported bends or compound curves require moulded plywood. A small number of specialised manufacturers produce moulded plywood.

Scarf jointed plywood is available from several sources. The scarf joint is fabricated with the same bond durability and quality as the plywood. Allowable bending stresses must be reduced by a multiplying factor of 0.8. Compression and shear stresses are unaffected.

Reference: Plywood Association of Australia