Interior Plywood:Plywoods for interior use only are made from various hardwood and softwood species, and can be used only in interior applications such as wall sheathing, furniture (where exposure to moisture is limited), cabinetry and the like. Interior plywood is available in most grades, as well as a number of hardwood species such as birch, oak and cherry.
Sanded Plywood:For cabinetry projects and other plans that require one side of the plywood to be visible to the user, sanded plywood would be the best choice. These are typically sold as A-C plywood, with one side sanded to A grade while the interior side, which will not be seen by the user would be a lesser C grade. Most hardwood plywoods are sanded A-C grades, but some SPF varieties are also sold as one-side sanded.
Exterior Plywood:The most common type of plywood, readily available at home centers. The glues used in exterior plywoods are much more resistant to moisture than interior plywoods. Once again, nearly all grades are available, with A-C, B-C and CDX the most common. Numerous hardwood species are also available in exterior varieties.
Marine Plywood:When moisture resistance is a priority, look into marine plywood. This type uses the best adhesives and is manufactured to the highest standards. It also is most commonly graded as A-A, with two top grade faces, but is limited in the hardwood choices that are practical for use in marine settings. Additionally, marine plywood is considerably harder to find and more expensive than other grades of plywood.
Structural Plywood:When the appearance of the face is of lesser concern than the strength and stability of the material, structural plywood will typically be the choice. The resins used to adhere the plies are designed for extra strength to avoid separating of the layers. Structural plywood is seldom found in a grade higher than C-D. It is commonly used in concrete forms on construction sites.