The ingenuity and technology that helped develop the plywood industry also assisted in the development of other materials in sheet form. The manufacturing processes for these materials are similar to the process for making plywood. The main ingredients for the building boards are vegetable or mineral fibers.
After mixing these ingredients with a binder, the mixture becomes very soft. At this point, the mixture passes through a press, which uses heat and pressure to determine the thickness and density of the finished board.
Sawdust, wood chips, and wood scraps are the major waste materials in sawmills. These scrap materials are softened with heat and moisture, mixed with a binder and other ingredients, and then run through presses that produce the density and thickness desired by the manufacturer.
The finished wood products that come off the presses are classified as hardboard, particleboard, oriented strand board (OSB), overlay plywood, and fiberboard.
Building Boards: Hardboard
Hardboard is a manufactured building material, sometimes called tempered board or pegboard. Hardboards are extremely dense.
These boards are resistant to water, but their edges are susceptible to the breaking if they are not properly supported. Holes must be pre-drilled for nailing; direct nailing into the material would cause it to fracture.
Three grades of hardboard are manufactured: standard, tempered, and service grade.
The next slide provides an explanation of each grade.
• It is light brown in color, smooth and can easily accept paint.
• It is suitable only for interior use, such as cabinets.
• Also known as Masonite, this hardboard is the same as standard grade except that in the manufacturing process, the standard board is coated with oils and resins and heated or baked to a dark brown color. In going through this process, the tempered hardboard becomes denser, stronger, and more brittle.
• It is suitable for either interior or exterior uses such as siding, wall paneling, and other decorating purposes.
Service Grade Hardboard
• It is not as dense, strong, or heavy as standard grade.
• The surfaces are not as smooth as standard grade.
• It costs less than other hardboards.
• It can be used for basically everything for which standard or tempered hardboard is used.
Building Boards: Particleboard
The main composition of this type of material is small particles or flakes of wood.
There are two types of particleboard: Type I and Type II.
• Type I is basically a mat-formed particleboard generally made with Vera-formaldehyde resin, suitable for interior applications.
• Type II is a mat-formed particleboard made with durable, moisture- and heat-resistant binders. This makes the particleboard suitable for interior and certain exterior applications.
Other Building Boards
High-density overlay (HDO) plywood panels have a hard, resin-impregnated fiber overlay that is heat-bonded to both surfaces.
Medium-density overlay (MDS) panels are coated on one or both surfaces with a smooth, opaque overlay.
Both HDO and MDO panels are manufactured with waterproof adhesive and are thus suitable for exterior use.