All About the Different Types of Plywood
Wood is the main constituent of many sheet goods. Some of these may be used in the main structural components of a house; others for decorative finishings.
Thin layers of wood, with the grain of each layer at a right angle to that of the previous layer, form plywood. Each layer is bonded tightly to the next, creating a very strong structure, and thickness adds further strength. Some plywoods are available as marine plies, which are impregnated with water-repelling chemicals.
Sheet materials such as MDF and particleboard are made from pieces of wood compressed together at high pressure. Water-resistant versions of these sheets are also available for use in areas where humidity may be high.
Cutting a Sheet
Using a handsaw
If the sheet is coated (with melamine, for example), mark the guide line on the side that will be visible and cut with this side facing upward. This is because the edge of the coating on the lower face will chip during cutting; this way, the chipped edges will be invisible. Score along the guide line on all sides of the sheet with a utility knife, and use a fine-toothed panel saw to reduce the chances of chipped edges.
Using a power saw
The blade cuts as it rises, so to avoid chipped edges on the visible side of a coated sheet, mark the guide line on the rear of the sheet and cut with the rear side facing upward.
To cut a straight line in a sheet of drywall, place a straight edge along the guide line, and score along it with a utility knife. Fold the sheet to snap it along the line, and cut through the paper backing.
Installing Plywood Subfloor: Plan Ahead
Plywood is rated for use, based on whether it’s for interior or exterior applications, and what type of material you plan to use for the finished floor. Available in standard sheets of 4 X 8 ft (1.2 X 2.5 m), your work will be easier if you minimize the number of cuts you need to make to cover the floor. Lay out your floor carefully before you start attaching sheets to the joists. Also, plan the layout so that the cut edges are against the perimeter of the room. Make sure the sheets are spaced evenly and butt each sheet tightly. The first step is to snap a line across the floor joists to mark the position of the first sheet of plywood.
Installing Plywood Subfloor: Leveling and Finishing
Check the butt joints of each piece of plywood to make sure the floor is level. If a sheet is raised, drive extra staples (or nails) to force the sheet into place. Using a flat trowel, cover all of the seams and fasteners with reinforced flooring patch. Sand the floor smooth with a hand sander.
Types of Plywood and Other Boards
3-ply and 5-ply: These common types of plywood get their name from their number of layers: e.g, 3-ply has three layers. Uses include: Boxing in or decorative internal uses
Multi-ply: This is composed of many layers. Uses include: Heavyweight construction, e.g., house framing
Blockboard: Not technically a ply, but shares its characteristics. Has two thinner outer layers that enclose thicker, square-cut lengths of wood. It is therefore stiff and durable. May have a decorative veneer or a finish of a lesser grade of wood. Uses include: Ideal for shelves and cabinets, and can be finished with paint
Medium-density fiberboard (MDF): Very versatile. Made up of highly compressed wooden fibers glued together. This method of manufacturing means that cut edges are neater than those on other materials. It can provide a rigid structural component, or can be intricately shaped to form a decorative surface ready for paint. Available in various thicknesses. Main drawback is that it gives off a very fine dust when cut, which must not be inhaled. Wear a mask when MDF is being cut. Uses include: Cabinets, cabinet doors, boxing in, shelving
Moisture-resistant MDF: A version of MDF that can resist moisture attack. It is often green. Uses include: Areas prone to moisture: e.g., kitchen or bathroom
Fiberboard: A lightweight version of MDF. Joints between sheets can be taped, and the boards painted. Uses include: Underlay for flooring, or as an alternative to drywall on a ceiling
Particleboard: Central core is composed of small wooden fibers. Has no decorative quality, so is usually covered. Some sheets fit together using a tongue-and-groove mechanism. Available in various thicknesses. Uses include: Often used as floor sheathing
Moisture-resistant particleboard: More water-resistant than normal particleboard. It is often colored green. Uses include: Flooring
Veneered particleboard: Has a melamine (plastic) or decorative wooden veneer. Uses include: Commonly used for shelves
Hardboard: Thin, compressed fiberboard. Standard hardboard has one smooth side, and one rougher side. Different grades and a variety of finishes are available. Uses include: Often used for parts of kitchen cabinets with a melamine (plastic) surface or veneer
Copyright 2009 Dorling Kindersley Limited
Text copyright 2009 Julian Cassell and Peter Parham
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