Plywood is a very common building material notable for its strength and durability. It is manufactured by sandwiching together thin sheets of wood. These thin sheets are called plies. The plies are laid across each other at 90-degree angles and then glued together. To bond the sheets permanently, the plywood is baked at high temperature and pressure. The quality of the plies of wood used as inputs determines the quality of the finished piece of plywood. Plywood is generally rated according to four grades, A, B, C, and D. It is also rated for interior and exterior use.
Grade A and B plywood contains few blemishes, knots, or splits. In Grade A plywood, any knot or split is repaired by the manufacturer with a synthetic filler. Marine plywood is typically of AA quality, with special sealants and glues for extra moisture resistance. The face of Grade A or B plywood is sanded smooth to make it easy to paint.
Grades C and D plywood are used for construction. They are suitable for roof sheathing and subfloors. Any piece of plywood will have a two-letter grade. Each letter indicates the quality of one face of the plywood sheet.
AA plywood is high quality on either side. Because either side can be finished, it is often used for furniture. Grade CDX plywood is low quality on either side but can withstand exposure to outdoor weather. That is why it is used in construction and framing. AC plywood is smooth on one side but rough on the other. This type of plywood can be used for many applications.
AC plywood can be used in some, but not all, types of furniture. Use AC plywood in situations where you want one side to look nice but the other side will never be visible. For this reason, AC plywood is suitable for the backer of pieces such as bureaus, dressers, and wardrobes. AC plywood can be used on some bookcases, but if the bookcase will be viewed from both sides, use AA plywood.
AC plywood has limited applications in making cabinets. Obviously, it is not suitable for the doors since these can be seen from both sides. AA plywood should be used for this. However, AC plywood can be used for the backs and sides of the cabinets in some places. You can also hide the C-side of the plywood by doubling up the sheets.
3. Trim Carpentry
AC plywood is used for soffits, fences, and base coatings.
4. Interior Walls
AC plywood can be used for wood paneling or framing interior walls, but should not be used for exterior walls. Only plywood with an X rating has suitable moisture resistance for exterior framing. Since the C side is construction grade, hang the plywood with the C facing out of the building. The better looking A side should face the interior of the room. The A side is much easier to paint, stain, or otherwise finish according to your tastes.