Monday, March 7, 2011
How-To: Drywall Installation Metal Trim and Corner Bead
FIGURE 3-1 Two types of corner bead (Courtesy of U.S. Gypsum Co.)
Corner bead is a strip of metal that has a 90° bend in it. The strip is usually eight to ten feet long. It’s made in different widths. The most commonly used is 1 1/4 inch. (See Figure 3-1.)
The edge of the corner bead sticks out enough so that when the bead is nailed to the wall and then covered (floated) with joint compound, the metal will be covered. This is done so the corner will have a hard edge, but it will not show when the wall is painted.
Corner bead is used not only for wall corners but also for window and door frames in place of wood. Figure 3-2 shows how to apply the bead to regular corners, and
Figure 3-3 shows how to apply the bead to window and door openings.
FIGURE 3-3 Corner bead details on windows
APPLYING THE CORNER BEAD
Before hanging drywall on the inside of a window, you must rasp the drywall around the edge of the window. If the drywall goes past the window edge. it will before you apply the corner bead that you check all the corners. Make sure that one drywall edge is not sticking out past the edge of another. Unless the corner joint is smooth and square, the corner bead will go on crooked.
Corner bead is difficult to apply correctly and requires care. If it’s done incorrectly, the bead won’t get covered when joint compound is floated over it. When applying the bead to a corner, put pressure against the bead as you nail it. Start nailing in the center of the bead and nail all the way to one end. Then nail the other end.
Each nail in a pair should be directly opposite the other, and the bead should be nailed about every twelve inches. Any loose part of the bead must be nailed down. When using the clincher or screw attachment, follow the same procedure. The corner bead on a soffit is nailed the same way as the other corners, but there is usually a corner of the soffit that uses three pieces of bead joining together from three different directions. These corner pieces are cut as shown in Figure 3-4.
Sometimes a builder will use plywood to cover the soffit. Most hangers will nail just anywhere, believing that it is acceptable to nail into the plywood. It is not. The plywood bounces when you drive a nail into it. This keeps the nail from holding tight. Even if the soffit is covered with plywood, you must place the nails in the stud. You will be able to tell where the studs are because the plywood will be nailed there. Some corners are less or greater than 90, so regular corner bead will not work on them. The finisher will have to use what is called flex bead. Such corners are called bastard angles. (See Figure 3-5.)
If you come upon a circular opening or archway that requires corner bead, cut the bead at one-inch intervals along one side of the angle so it can be bent around the opening. Refer to Figures 2-42 through 2-44.
A plastic corner bead is available now for corners that are not square. If you cannot find it, the angle of a piece of metal bead can be made wider by fitting a one-inch piece of pipe inside the metal corner bead. Tap it with a hammer until the angle is the desired size.
Another convenient new product is the bullnose corner bead. This gives a rounded-off look. This metal is put on in almost the same way as regular corner bead except, of course, the angle cuts are much harder to make. Flannery, Inc., also sells two metal pieces that help match the corners so they can be finished properly.
See Figures 3-6 and 3-7.
OTHER METALS YOU SHOULD KNOW ABOUT
Expansion Joints or Control Joints
CUTTING THE MITER
1. For cutting miters in an archway, install the header bead first. The bead should extend from the framing on one side to the framing on the other side with a simple straight cut.
2. Cut a small piece of bead approximately 6" long to be used for a guide. With a pair of snips cut a half moon section out of each end as shown in the illustration, and trim to fit the header bead. When you have accomplished this, simply cut the two vertical beads to length and with the small guide, place it over the bead, and scribe the half moon shape. Cut on the line and nail the beads in place.
FIGURE 3-7 Bullnose corner bead (Courtesy Flannery, Inc., Pacoima, CA)
METAL FURRING CHANNEL
Metal furring channel can be used to build suspended drywall ceilings. It also can be used to furr a wall area, creating air space for soundproofing. This channel is used for many other things as well. (See Figure 3~8.)
METAL STUDS AND RUNNERS
Metal studs and runners are used in the metal framing industry. You will see metal framing on most commercial job sites. Metal framing will affect your work as the work. If you push in too much when driving the screws, the studs will twist; this in turn twists the drywall. The problems caused by twisting the studs usually aren’t noticed until you start finishing. Even though the recess is filled and smoothed out, the edge of the recess is showing and it may be difficult to figure out the reasons for this. If you take a long piece of metal and place it across the wall, you will understand the problem more clearly (Figure 3-9).
FIGURE 3-9 Sometimes these joints take in the entire piece of drywall to break the section out