Metal corner bead can be installed with nails, screws or staples. Screws must be used on metal studs. One challenge with using metal fasteners on the metal bead is the tendency for them to push the bead in one direction or another. Although metal corner bead has holes in various locations. You may need to screw directly through the metal on the bead instead through the pre-punched holes. Drywall tape can also be used, though this is rarely done. However, we have found that the metal bead that has been taped on with drywall tape rarely cracks.
Choosing Joint Compound
For a durable finish use setting-type joint compound, or mud, for the first coat over the metal. Ready-mixed can be used for the second and finish coats, but it’s too soft and prone to shrinking when used in a thick application like that required to cover metal corner bead. Work quickly when using setting compound to be sure it doesn’t harden before you’re done.
Cut the Bead to Length
Measure the length with a tape measure and cut a piece of bead for each outside corner. Use a pair of tin snips or scissors to cut in from each side of the metal and then bend it, in the middle to break it apart.
Attach the Bead with Drywall Screws
Hold the bead against the corner while pressing hard on the peak with your palm to flatten it tightly to both walls. Start near the top and drive a 1 5|8 or 2 inch drywall screw through one of the small holes in the metal and into the wall frame. Drive a screw into the opposite wall at about the same level, but not directly across, to hold the bead in two places. Sink the heads of the screws deep enough to slightly kink the metal and make a small depression in the drywall. If the screws are not driven far enough below the surface of the wall, the heads will show through the mud and be very visible. Move along the length pressing at each point and driving the screws at about 12 inch intervals along both walls. Check to be sure the metal is flat the full length of the wall. Run a joint knife over it to check for any spring in the metal and drive a screw at any loose edges.
Cover the Corner with Joint Compound
Use a 6 inch drywall joint knife to apply a thick coat of setting-type joint compound in crossing strokes along both walls, from one end to the other. Use a very thick coat that covers all the metal and spreads well onto the the drywall. Remove the excess mud to float the surface into the corner. Rest one side of the knife blade on the bead peak and the other against the drywall. There will be a slight dip in the wall where the two meet, float the knife over this dip to fill it in with a solid coat of mud. Stroke starting at the end and keep the knife straight as it rides along both surfaces. Don’t push too hard on the blade to avoid bending it and causing a depression in the mud coat. Float the blade to keep the mud as level as possible.