Plywood is a structural wood product consisting of thin sheets of wood veneer known as plies. The plies, typically three to five, are cross-laid at 90-degree angles for strength and bonded together with resins under heat and pressure to form a single structural panel typically 4 feet wide and 8 feet long. Plywood comes in different quality grades for different applications.
Each ply making up a plywood panel is graded according to the number of knots, voids and other natural defects it has, with Grades of A, B, C, D and X. Grade A has virtually no defects and Grade X has lots of defects. Plywood graded BC has a Grade B face and Grade C inner plies and backside. Knots and other defects on the B-grade face have been filled in with veneer patches and the face sanded smooth for application of paint, varnish or other finish. BC plywood is an exterior product intended for applications where the panel will be exposed to weather and moisture. BC plywood is exceptionally strong and stiff. It is generally available in 1/4-, 3/8-, 1/2- and 3/4-inch thicknesses.
BC Plywood Uses
Sanded BC plywood is a utility panel used as exterior wall sheathing or as a base for attaching siding materials. It is used in residential and commercial construction for new structures and for remodeling existing structures. It is often used for soffits, building stairs, as the support structure for cabinets and other built-ins, for shelving and for paneling. It can be fastened to structural framing with nails or screws.
Plywood panels sold in the United States are stamped with grade marks in a format specified in National Plywood Standard PS 1-83. The marks will specify whether the panel is for “interior” or “exterior” use, the face side grade and the back side grade. For instance, a panel marked “Exterior/Grade B-C” would indicate it is for use in outside structural work and that it has a smooth, paintable B-grade surface on one side and a rougher C-grade surface on the other. Panels will also bear the manufacturer’s name and trademarks.
BC plywood panels should be stored flat, under a roof if possible and be protected from the weather until you are ready to use them. If storing outdoors, place panels on at least three 4-by-4-inch beams to keep them off the ground and cover them with an opaque plastic sheet or tarp fastened at the corners of the stack. Never lean panels against a wall for more than a short time because they will bend and warp.