Plywood is a durable building material, commonly found in houses. Plywood has many uses, including sub-flooring, roof sheaths, and exterior structural panels. Plywood sheets are available as structural, interior, exterior or marine use. Manufacturers take very thin sheets of wood and bond them together with adhesive. Exterior plywood employs the use of lower wood grades and weather and moisture resistant bonding agents to ensure the strength and durability of the sheet. Interior plywood, while no less strong or durable, uses higher grades of thin wood. The most common causes of plywood warping is changes in moisture and humidity and plywood sheets being stored upright rather than flat.
Locate a flat, dry surface large enough to accommodate the plywood sheet.
Lay the plywood sheet down with bow up. The corners of the plywood will rest on the surface and the middle will stick up like an inverted bowl.
Place heavy weights at the corners and on top of the bowed section. If other areas of the plywood are not touching the ground, place weight on top of those areas. Allow the weight to remain on top of the plywood until the plywood straightens. The length of time will depend on humidity and the degree of the warp.
Use lumber, straight plywood or metal weights to weigh the plywood down. Store plywood on a flat, dry surface to prevent warping.