Outside drywall corners do not come to a smooth, even seam. To make where the ends meet more attractive, corner beads must be installed. Luckily for homeowners, installing corner beads and mudding them is one of the easier parts of the drywall process.
When you install beads, apply light pressure on the bead itself toward the corner. That will help ensure that the strip registers evenly along both walls and runs in a straight line. Misalignment can make the bead twist up the corner, and your only remedy is to rip it off and try again. Always buy spare bead. That will give you some backup material in case a strip gets bent or if a miter is miscut. Mudding beads is also relatively easy because you have the corner to guide one edge of your knife as you spread the compound. Avoid excessive pressure because that will curve the blade of your knife, resulting in an underfilled concave corner.
There are two different techniques you can use to create corner beads: Metal corner bead for crisp corners or bullnose bead for rounded corners. Choose what works best for your space and follow our steps below.
At an outside corner, lap one sheet of drywall over the other and fasten it to the stud. Make sure the end of the lapped sheet doesn't extend past the face of the other wall. If it does, rasp away the excess material. You don't have to achieve a perfect junction because the corner bead establishes the finished corner.
Cut the corner bead to length with tin snips, keeping its bottom end about 1/2 inch off the floor. (Baseboard molding will conceal any gap at that end.) Lightly press on the corner of the bead, squaring the legs of the strip against the walls. Drive a few nails through the holes in the metal strip to establish its position, then nail through the metal for a more secure hold. Don't twist the bead or press it too tightly as you install it. Space the nails about 8 inches apart along each leg; make sure they are seated firmly.
Use a 6-inch drywall knife to apply the first coat of compound to the corner. The blade of the knife glides along the raised bead and the wall, laying the mud into the valley between these two high points. Don't try to build too much thickness with this first coat or you'll risk cracking. Note that filling the tapered seam first gives the knife a continuous bearing surface across the joint.
For the second coat, choose a 10-inch knife, and again bridge between the metal corner and the surface of the wall. Feather the compound along the wall to create a smooth transition. Use a 12-inch knife for the third coat to feather the compound even further onto the wall.
With bullnose bead, you may need to install the drywall sheets so that they terminate flush with the corner of the framing. This placement is sometimes necessary to create clearance for the inside radius of the strip. Purchase bullnose bead strips before you hang the drywall to determine the proper corner treatment.
Nail the metal or vinyl bullnose bead into place, spacing the fasteners about 8 inches apart along each leg. If your outside corner is significantly larger or smaller than 90 degrees, ask a drywall supplier about the availability of off-angle bullnose beads. Make sure the materials you'll need to execute your design are available before you begin work. Composite materials can adapt to square or off-angle applications.
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