Proper plywood storage is important to prevent damage caused by warping and rotting. Because plywood is a composite of smaller pieces of wood, it is held together with adhesives that contain water. This makes it more susceptible to warping or bending because the adhesive is not strong enough to maintain the shape of the large sheets on its own. Plywood should be stacked and stored horizontally for the best protection against warping.
Cover the pallets with plastic sheeting to protect the plywood from moisture that could lead to mildew and rot. Overlap the edges if using more than one sheet.
Stack the plywood, placing the largest pieces on the bottom, and so on up. Sheets can be stacked as high as you like, as long as the pallets on the bottom are not broken and can support the weight.
Cover the plywood with another layer of plastic sheeting. Keep it covered at all times. It may seem like a hassle to unstack the plywood whenever you need a piece, but this method ensures minimal warping.