Being able to properly hang drywall corners is a skill that can save you big bucks if you own a home. Basement renovations, new room additions, or garage conversions can mean savings if you can put up drywall yourself. Outside corners are tricky and the hardest to accomplish because if not done properly, the edges will be an eyesore to the entire room.
Step 1: Hang the Drywall
If the drywall has been installed correctly on properly framed walls, the final piece of drywall should line up perfectly with the outer edge of the outside corner. If it does not, then cut a piece of drywall to fit with about 1/8-inch narrower to backset slightly from the corner. Make sure the piece of drywall fits snug against the adjoining sheet, possibly using a prybar under the sheet being hung to lift it snug if you are hanging the drywall on the walls. If you are hanging the drywall on a ceiling, then be sure to use a drywall jack so that you do not have to constantly fight to keep the piece of drywall in place. Screw or nail the piece into place, making sure that they are just slightly sunk at least every 7 to 8 inches into every stud.
Step 2: Cut and Hang the Corner Bead or Bullnose
After both pieces of drywall are properly hung, measure the length of metal (or plastic) trim needed and cut it to the right length with some slack to spare, making it easier to adjust in place. Hold the corner bead or bullnose tight onto the corner and leave a small gap on each end, evenly split between the ceiling and the floor. Screw or nail the piece into place. Do not use the holes directly opposite each other on both facades to avoid bending or warping the trim. You should instead use alternate holes from one face to the other.
Step 3: Plastering the Corner
Using a small trowel, scoop some mud out of the bucket or box, and spread it onto each side of the corner bead or bullnose. Starting from the top, use a slight, even pressure to force the compound into the trim while bringing the trowel downwards towards the floor, wiping off any excess buildup of mud. Only a thin coat of the compound, just enough to cover the trim, should be applied to the joint. Let the mud thoroughly dry, and then repeat with the second application of an even thinner coat, using a wider trowel to spread out an even and wider layer. Repeat this step 3 times, going wider every time, without creating excessively high spots, until the area is built up enough to be sanded level and flat with the drywall.
Hanging drywall is a job that has to be learned, and the more you do it, the better you will get. Properly joining 90-degree inside corners can be trying at first, but by following the directions above, you will soon be hanging drywall like a professional.