SUSPENDED ACOUSTIC CEILING SYSTEMS
Suspended acoustical ceiling systems can be installed to lower a ceiling, finish off exposed joints, cover damaged plaster, or make any room quieter and brighter. The majority of the systems available are primarily designed for acoustical control. However, many manufacturers offer systems that integrate the functions of lighting, air distribution, fire protection, and acoustical control. Individual characteristics of acoustical tiles, including sound-absorption coeffic
ients, noise-reduction coefficients, light-reflection values, flame resistance, and architectural applications, are available from the manufacturer.
Tiles are available in 12-to 30-inch widths, 12-to 60-inch lengths, and 3/16- to 3/4-inch thicknesses. The larger sizes are referred to as "panels." The most commonly used panels in suspended ceiling systems are the standard 2-by 2-foot and 2- by 4-foot acoustic panels composed of mineral or cellulose fibers.
It is beyond the scope of this training manual to acquaint you with each of the suspended acoustical ceiling systems in use today. Just as the components of these systems vary according to manufacturers, so do the procedures involved in their installation. With this in mind, the following discussion is designed to acquaint you with the principles involved in the installation of a typical suspended acoustical ceiling system.
PREPARATION FOR INSTALLATION
The success of a suspended ceiling project, as with any other construction project, is as dependent on planning as it is on construction methods and procedures. Planning, in this case, involves the selection of a grid system (either steel or aluminum), the selection and layout of a grid pattern, and the determination of material requirements. Figure 5-17 shows the major components of a steel and aluminum ceiling grid system used for the 2- by 2-foot or 2- by 4-foot grid patterns shown in figure 5-18.
Figure 5-17.Grid system components.
Figure 5-18.Grid layout for main tees.
The layout of a grid pattern and the material requirements are based on the ceiling measurements and the length and width of the room at the new ceiling height. If the ceiling length or width is not divisible by 2 (that is, 2 feet), increase those dimensions to the next higher dimension divisible by 2. For example, if a ceiling measures 13 feet 7 inches by 10 feet 4 inches, the dimensions should be increased to 14 by 12 feet for material and layout purposes. Next, draw a layout on graph paper. Make sure the main tees run perpendicular to the joists. Position the main tees on your drawing so the border panels at room edges are equal and as large as possible. Try several layouts to see which looks best with the main tees. Draw in cross tees so the border panels at the room ends are equal and as large as possible. Try several combinations to determine the best. For 2- by 4-foot patterns, space cross tees 4 feet apart. For 2- by 2-foot patterns, space cross tees 2 feet apart. For smaller areas, the 2- by 2-foot pattern is recommended
As indicated in figure 5-17, wall angles and main tees come in 12-foot pieces. Using the perimeter of a room at suspended ceiling height, you cart determine the number of pieces of wall angle by dividing the perimeter by 12 and adding 1 additional piece for any fraction. Determine the number of 12-foot main tees and 2-foot or 4-foot cross tees by counting them on the grid pattern layout. In determining the number of 2-foot or 4-foot cross tees for border panels, you must remember that no more than 2 border tees can be cut from one cross tee.
Figure 5-19.Wall angle installation.
The tools normally used to install a grid system include a hammer, chalk or pencil, pliers, tape measure, screwdriver, hacksaw, knife, and tin snips. With these, you begin by installing the wall angles, then the suspension wires, followed by the main tees, cross tees, and acoustical panels.
The first step is to install the wall angles at the new ceiling height. This can be as close as 2 inches below the existing ceiling. Begin by marking a line around the entire room to indicate wall angle height and to serve as a level reference. Mark continuously to ensure that the lines at intersecting walls meet. On gypsum board, plaster, or paneled walls, install wall angles (fig. 5-19) with nails, screws, or toggle bolts. On masonry walls, use anchors or concrete nails spaced 24 inches apart. Make sure the wall angle is level. Overlap or miter the wall angle at corners (fig. 5-20). After the wall angles are installed the next step is to attach the suspension wires.
Figure 5-20.Corner treatment.
Suspension wires are required every 4 feet along main tees and on each side of all splices (see fig. 5-21). Attach wires to the existing ceiling with nails or screw eyelets. Before attaching the first wire, measure the distance from the wall to the first main tee. Then, stretch a guideline from an opposite wall angle to show the correct position of the first nail tee. Position suspension wires for the first tee along the guide. Wires should be cut to proper length, at least 2 inches longer than the distance between the old and new ceiling, Attach additional wires at 4-foot intervals. Pull wires to remove kinks and make 90° bends in the wires where they intersect the guideline. Move the guideline, as required, for each row. After the suspension wires are attached, the next step is to install the main tees.
Figure 5-21.Suspenslon wire installation.
In an acoustical ceiling, the panels rest on metal members called tees. The tees are suspended by wires.
Figure 5-22.Main tee suspension and steel splice.
Figure 5-23.Main tee and aluminum tee splice.
Figure 5-24.Aluminum cross tee assembly.
Figure 5-25.Steel cross tee assembly.
Panel installation is started by inserting all full ceiling panels. Border panels should be installed last, after they have been cut to proper size. To cut a panel, turn the finish side up, scribe with a sharp utility knife, and saw with a 12- or 14-point handsaw.
Most ceiling panel patterns are random and do not require orientation. However, some fissured panels are designed to be installed in a specific direction and are so marked on the back with directional arrows. When installing panels on a large project, you should work from several cartons. The reason for this is that the color, pattern, or texture might vary slightly; and by working from several cartons, you avoid a noticeable change in uniformity.
Since ceiling panels are prefinished, handle them with care. Keep their surfaces clean by using talcum powder on your hands or by wearing clean canvas gloves. If panels do become soiled, use an art gum eraser to remove spots, smudges, and fingerprints. Some panels can be lightly washed with a sponge dampened with a mild detergent solution. However, before washing or performing other maintenance services, such as painting, refer to the manufacturers instructions.
Ceiling tile can be installed in several ways, depending on the type of ceiling or roof construction. When a flat-surfaced backing is present, such as between beams of a beamed ceiling in a low-slope roof, tiles are fastened with adhesive as recommended by the manufacturer. A small spot of a mastic type of construction adhesive at each corner of a 12-by 12-inch tile is usually sufficient. When tile is edge-matched, stapling is also satisfactory.
Perhaps the most common method of installing ceiling tile uses wood strips nailed across the ceiling joists or roof trusses (fig. 5-26, view A). These are spaced a minimum of 12 inches OC. A nominal 1- by 3-inch or 1- by 4-inch wood member can be used for roof or ceiling members spaced not more than 24 inches OC. A nominal 2- by 2-inch or 2- by 3-inch member should be satisfactory for truss or ceiling joist spacing of up to 48 inches.
Figure 5-26.Ceiling tile assembly.
In locating the strips, first measure the width of the room (the distance parallel to the direction of the ceiling joists). If, for example, this is 11 feet 6 inches, use ten 12-inch-square tiles and 9-inch-wide tile at each side edge. The second wood strips from each side are located so that they center the first row of tiles, that can now be ripped to a width of 9 inches. The last row will also be 9 inches, but do not rip these tiles until the last row is reached so that they fit tightly. The tile can be fitted and arranged the same way for the ends of the room.
Ceiling tiles normally have a tongue on two adjacent sides and a groove on the opposite adjacent sides. Start with the leading edge ahead and to the open side so that it can be stapled to the nailing strips. A small finish nail or adhesive should be used at the edge of the tiles in the first row against the wall. Stapling is done at the leading edge and the side edge of each tile (fig. 5-26, view B). Use one staple at each wood strip at the leading edge and two at the open side edge. At the opposite wall, a small finish nail or adhesive must again be used to hold the tile in place.
Most ceiling tile of this type has a factory finish; painting or finishing is not required after it is placed. Take care not to mar or soil the surface.