Other types of plywood are manufactured for specific purposes. Among these types are the structural, sheathing, overlaid panels, decorative panels, and concrete form panels. Table 6-3 lists some of the various types of plywood with their suggested uses.

Structural plywood is recommended for heavy-load application where strength properties are of great importance. Likewise, for box beams, gusset plates, and stressed-skin panels, unsanded grades of C-D plywood are recommended. Standard plywood sheathing is used for subfloors, roof decks, and wall sheathing.  It is

Table 6-3.-Uses of Plywood

recommended for use in spaces that may be exposed to moisture during construction, but will be covered when construction is complete. Overlaid panels have a resin-treated fiber-surfacing material, on one or both sides, to hold paint and finishes more readily. These exterior or interior types of plywood are recommended for use in furniture, cabinets, millwork, and exterior trims.

Decorative panels are used basically for exterior and interior wall sheathing. Both types are manufactured in a multitude of designs and patterns and can be painted, stained, or left to weather naturally.

A concrete form panel has a coating over its exterior face to make it moisture-resistant and nonadhesive to concrete when used as forming material. The exterior coating reduces the number of times the form must be oiled and allows the panel to be reused several times.

For various reasons, many common construction materials are used as wood or plywood substitutes. Some are significantly less expensive than plywood; others are more suitable because of their decorative appearance and weather-resistant qualities.

Particleboard, commonly referred to as chip-board or flakeboard, is produced by mixing a resin-bonding agent with wood particles and bonding them together by means of heat and pressure. The use of particleboard is limited to nonstructural use because of its low strength qualities. The most common size sheets are 4 ft by 8 ft and vary from 1/4 in. to 1 1/2 in. thick.

Hardboard is made of compressed wood fibers subjected to heat and heavy pressure. The finish may be obtained in a plain, smooth surface or in any number of glossy finishes, some of which imitate tile or stone. Its strength is about equal in all directions, and it can be bent into various shapes. Hardboard is available in thicknesses from 1/8 in. to 3/8 in. The most common size sheets are 4 ft by 8 ft.

Fiberboard is made of wood or vegetable fiber that has been compressed to form sheets or boards. They are comparatively soft and provide good insulation and sound-absorbing qualities. Fiberboard is available in sizes from 1/2 in. to 1 in. thick, 2 ft to 4 ft wide, and 8 ft to 12 ft long.