Wood Products: Plywood and Paneling | |
To make plywood, logs are sliced or peeled into thin layers or plies and then two or more plies are bonded together with adhesives to make plywood panels. Depending on the quality of the outer wood plies, the plywood may be graded from A through D. For example, oak plywood may be graded "A-A," meaning that both sides or faces of the plywood are high quality and free of knots or other blemishes. A-A plywood is used for cabinetry or other uses where both sides will be exposed to view -- for example, for kitchen cabinet doors. For rough use, where strength is important but appearance is not, the plywood might carry a C-D rating, meaning that one side may have splits or tight knots, the other side may have unrepaired knotholes. C-D grade plywood is the designation for sheathing plywood, used as subfloor or for wall or roof sheathing, where it will be covered with either siding or roofing and appearance is not important. Where one side or surface on plywood is better than the other, for example "A-C," the best or A side is called the face. Plywood also is graded according to its moisture exposure rating. Plywood that is marked "exterior" is made with waterproof glue, as is "marine" plywood, which is commonly used for boat construction. "Exposure 1" plywood means the plywood can be used for sheathing, and will later be protected by siding or roofing. Sheathing grade plywood will also have a span rating, shown on the grade label; i.e.: 32/16 span rating means that the plywood can be used with a truss span of 32-in. on a roof, but only a 16-inch span is allowed over floor joists. The lower 16-in. span limits for floor use is because the floor will carry a live load rating, which means that the floor will have to support the weight of people, furniture, and appliances; i.e., a live load or that weight in addition to supporting the building itself. See the sample Plywood Markings illustration for a complete review of plywood markings information and its meaning. The interior or center ply construction of a sheet of plywood can also be important. For example, for some sheathing plywood it is not important that interior or core plies might have large voids or knot holes, as long as strength is not affected. For furniture or cabinet making, hollows or voids in interior plies will show up as rough damaged edges (called "core gap") when the plywood is cut into a table tops or made into cabinet drawer fronts or doors. For some furniture applications the plywood may be designated as "lumbercore," meaning the center ply is made of solid lumber. Lumbercore is a superior choice for making furniture or cabinets. Paneling Paneling is a versatile material, usually used to cover walls but also used for its dramatic effect on ceilings. When used on ceilings, the 4x8 sheets of paneling are installed over wallboard, and nailed or glued in place. The panels are installed perpendicular to the joist direction, and then wood beams are installed at 4-ft. intervals, or 4 ft. o.c. (on center, or center-to-center). This technique means that the wood beams will cover the end joints of the paneling, so there are no unsightly butt joints to mar the project. Paneling may be made of solid wood plies, either finished or unfinished, in any one of dozens of colors, wood tones, and wood species. Or, it may be made of hardboard, with a vinyl photo image of wood grain laminated to the base material. The prefinished variety, used most often by the do-it-yourselfer, is usually sold in 4 ft. x 8 ft. sheets, in thicknesses of 3/16 in. to 5/16 in. Solid wood paneling such as knotty pine or pecky cypress is often sold in tongue-and-groove planks. The planks are usually 3/4 in. thick, so no backer board is needed as a base for solid wood paneling. However, you must nail 2x4 nailers between the studs or joists to provide bearing and nailing surfaces. The thin sheets of prefinished paneling are not made to be installed directly over stud walls. The panels are too thin, are noisy, and will often warp and become wavy between the studs. Instead, a layer of 3/8-in. thick wallboard must be applied over the studs, then the paneling is glued or glued and nailed over the wallboard. This technique results in a wall that is as thick as plaster (3/8 in. + 3/8 in. = 3/4 in. thick) and has good stiffness, soundproofing, and resistance to impact damage. This strength, plus the ease of cleaning paneling, makes it a prime choice for game or recreation room walls, for wainscoting in kitchen or dining rooms, and for halls or entry foyers. In addition, the warm wood look enhances the appearance of office or study rooms. Painted nails, with heads colored to match the color or tone of the paneling, can be used for installing paneling. If you use nails, choose nail locations carefully to try to hide them from view. For example, position the nails in the wood grooves of the paneling, or in knots or wood grain where the nail holes will be less visible. The best way to install paneling is to use a panel adhesive such as Liquid Nails or PL200. Make all the paneling cuts and cutouts and test fit the panel in place to be sure it fits. Then use a caulk gun to apply an "S-shaped" or serpentine bead over the back side of the panel. Position the panel against the wallboard backer material and hang it in place with a couple of nails driven at the top edge of the panel. Push the panel against the wallboard so that it has full contact with the panel adhesive, then pull the panel away from the wall so air can reach the adhesive. Then push the panel against the wallboard backer and use the side of your fist or a padded 2x4 block and hammer to tap on the face of the board and ensure full adhesive contact between the panel and the wallboard backer. If necessary, drive a couple of extra nails along the bottom edge of the panel, where the nailheads will be covered by base trim, to hold it in place until the adhesive cures and provides full panel support. Buy your paneling at least one week in advance of the installation job, to give the material a chance to acclimate, or come into temperature and moisture balance with the area where it will be installed. Paneling manufacturers point out that paneling that has been properly handled, transported, and stored should not shrink at the jobsite. That is true, but we do not know how the material has been handled, and nothing is lost if we follow the old carpenter's rule of letting all materials acclimate before we install them. This is simple insurance against having the materials shrink or swell in place, resulting in panels with shrinkage gaps at the joints or panels that buckle from expansion. A buyer's tip: Because paneling is moved about using fork lifts, the ends of paneling sometimes get bumped and damaged. This, of course greatly reduces the value of the paneling, because it cannot be sold for installation on walls that are a full 8-ft. high. Often, however, the do-it-yourselfer may plan a job where the wall to be covered is not a full 8-ft. high, for example, in a basement or attic expansion where ceilings are less than 8-feet high. TIP: Measure the height of the paneling you will need and calculate how many inches must be cut off each panel. Then shop the reject section of the home center for end-damaged paneling. You may get a bargain, because the damaged end of the panels must be cut off anyway. This way, you may buy a high grade of paneling at distress prices, perhaps for less money than you would pay for the cheapest grades. The paneling you choose will depend on your own tastes and budget. As in all purchases, keep in mind that a few dollars extra cost per panel should not convince you to buy the cheapest paneling. Remember, you will have to live with your choice a long time, and look at it daily. Written by Gary Branson Reprinted with permission. Copyright HouseNet, Inc. |