Plywood

Подпись: Copyright © Marcel Dekker, Inc. All rights reserved.Plywood is used as sheathing that contacts concrete for job-built forms and prefabricated form panels. Since plywood comes in large sizes, it saves forming time. Plywood is made by gluing to­gether thin layers of wood, called veneer, under intense heat and pressure. Most plywood panels are made of softwood. Many spe­cies of trees are used to make plywood, such as Douglas fir and Southern pine. The grain of each ply is laid at a right angle to the adjacent pieces. This process gives plywood extra strength and reduces shrinkage and swelling.

Plywood is commonly sold in large sheets 4 X 8 ft (1.22 X 2.44 m). These large panels reduce erection and stripping costs and produce fewer joints on the finished concrete. Plywood is avail­able in varieties of thicknesses that identify it for sale. For example, plywood called “V2 in. (12.7 mm) plywood’’ is 1/2 in. (12.7 mm) thick. In contrast to the situation with lumber, actual and nominal thick­ness for plywood is the same; 1 in. (25.4 mm) plywood is 1 full inch (25.4 mm) thick.