Plywood is made by sandwiching together multiple thin sheets of wood layered and positioned at right angle to each other and glued into a block. Unlike OSB, which is made from a slurry of wood chips glued into a block, plywood consists of solid and continuous layers which reinforce each other. Plywood comes in several different grades and styles. The grade of plywood is determined by its quality and also by its use. The front and back faces of the finished piece of plywood are assigned a letter such as A, B, C, or D.
Type A and B plywood is virtually free of knots and the faces are sanded smooth for painting. This type of plywood is often used for furniture and cabinetry. On the other hand, type C and D plywood are of lower quality. Grade C plywood can have knots up to 1.5 inches in diameter, and Grade D plywood can have knots up to 2.5 inches in diameter. Neither grade is sanded smooth at the face. This type of plywood is used for construction purposes. The X indicates it is treated with an adhesive that can withstand limited exposure to moisture. CDX plywood is used to build roof sheathing and subfloors.
Step 1 – Obtain Materials
Large sheets of plywood will require the use of a special hydraulic press to apply an even and tremendous surface pressure between two plates that will bring a uniform thickness over the whole surface of the sheet. The sheets are also made slightly larger than required to be later recut to size. Without the proper equipment, only smaller size pieces of plywood can be made in the following manner.
The first step in making your own plywood is to obtain plies of wood. You can purchase these from a hardware store or some craft stores, or you may be able to shave them from a roller log yourself. Cut each ply to the length and width of the finished sheet. For construction purposes, softwood is more easily available and favored, usually Fir or Spruce. Because this is CDX plywood, it does not have to be extremely high quality. Using higher quality wood than you need will only waste money.
There is no need to sand the faces smooth or fill in knots and cracks. You will need enough plies to reach the desired thickness. For construction plywood, generally, at least 5 plies are used. Select plies with medium-sized knots for the front face, and plies with large knots for the rear face. You will need a water-resistant epoxy or resin to glue the plies together. Marine plywood utilizes phenol-formaldehyde glue for extra resistance to water submergence and against wood rot.
Step 2 – Stack and Glue Plies
Lay the first ply flat on the workspace. Coat the surface with glue and use a squeegee or straightedge to work the glue into the crevices of the grain. Scrape off any excess glue and lay the second ply on top of the first. Lay the plies so that their wood grains are perpendicular. Push the second ply firmly onto the bottom and line up the edges, and then begin applying glue to the second ply. Continue the process until all the plies have been stacked.
Step 3 – Clamp and Dry
Cover the finished piece of plywood with wax paper and fasten it in place with clamps. Stack bricks, water jugs, or other loads on top of the piece for additional weight. Give it at least 24 hours to dry and test its strength before using it in construction.