Exterior Grade Plywood Density

About Plywood

Plywood is a manufactured wood material that is composed of thin layers of wood that is glued together with adjacent layers set at right angles to each other for greater strength. It is then pressed together for a solid and durable wood surface that can be used for a variety of construction applications. One of the advantages of using plywood over traditional wood is it resistance to warping. The density of the plywood is related to the number of plies, or layers in the material.

Plywood comes in several grades that are used for special purposes. A-grade plywood is smooth with few knots and a veneer that is suitable for painting. B-grade plywood has more flaws that are filled. C-grade has more repaired flaws and larger knots and discolorations. The flaws in D-grade plywood have not been repaired and may be unsanded. Plywood is also available in both interior and exterior types that come in several grades. Plywood is generally marked with an “X” for exterior use or an “I” for interior use. Plywood also is categorized as Type I and Type II. The adhesives used in Type I plywood is able to resist exposure to the elements, according to the Home Depot website.

Exterior grade plywood also come in a range of grades. These categories are generally based upon difference in appearance in grades A to D. Those types with a more refined appearance, generally A and B grade, can be used for painted surfaces, while those that are less refined are used as underlayment and support materials.

Exterior grade plywood is used for many purpose on building envelopes, that is, the exterior surfaces of buildings. It is used for cladding on siding, walls, partitions, roof linings and other miscellaneous purposes, according to the Gunnersens website. Plywood may be used for shed construction, with the more attractive surfaces used on the exterior and the less refined surfaces turned in toward the interior. Lower grades of exterior plywood are used for shutterboxing boxes, those structures built to contain concrete as it is poured and set. Marine grade exterior plywood is used for applications in marine environments where extensive exposure to moisture is a problem.