Construction CD & OSB
Construction plywood will have a "C" grade face and a "D" grade back. This means that there can be missing knots in the veneer, voids under the veneer and a rough face and back. CD plywood will often be warped and will not lay flat until fastened into place. It is generally used for roofs, walls and subfloors. Plywood thickness is nominal. 1/2" CD plywood is closer to 15/32", 5/8" is 19/32", 3/4" is 23/32".
OSB is made with wood chips that are randomly orientated to give the panel stength. There is a smooth face and a sanded/rougher face. The panels will not have voids and will generally lay flat. They are not designed for continuous exposure to the weather and may swell if exposed to moisture. They can be used for roof and wall sheating and for subfloors.
