Plywood is made from thin sheets of wood. The layers are glued together so that adjacent plies have their wood grain at right angles to each other for greater strength. It is flexible, cheap, workable, re-usable, and resistant to cracking, shrinkage, and twisting/warping. All sized 4’x8’ (1.22m x 2,.44m) and in different thicknesses ranging upto ¾”, in different qualities.
Interior use plywood is made from various hardwood and softwood species: Virola, Cedar, Amescla, Oukume, Birch, Poplar, Pine, etc. and is used in interior applications such as wall sheathing and furniture, cabinetry and the like where exposure to moisture is limited.
Exterior use plywood is much more resistant to moisture than interior plywood, specially if its treated with dispersed copper azole. CDX is the most common type of plywood; however different qualities are available:
Pine Plywood: typically used for construction and industrial purposes
CDX: the most popular type of plywood used for rough construction. This plywood is tough enough to withstand a some exposure to moisture. Generally used for roof sheathing – in between shingles and roofing felt; on walls, between siding and insulation, and sub floors, below the carpet. And most important is a relatively cheap material for constructing large scale projects, like housing. It can be pressure treated.
OES: is a better grade than CDX, given it is treated to have its edges oil sealed. Usually used for Concrete Forming.
T1-11® which is just exterior plywood with different face treatments and groove patterns to emulate a traditional board and batten design