After installing drywall in a room and taping/bedding the straight joints and seams, you’ve now reached the point for installing drywall taping metal corners. Most pros say that for the inside corners of a wall, metal corners are not necessary. But outside corners endure much more wear and tear during the lifetime of a wall, so it’s a good idea to reinforce them with some type of extra material to support and strengthen them.
Drywall taping metal corners are sometimes called metal corner beador metal corner strips, and some reinforcing corners come not only in metals such as galvanized aluminum or steel, but also in plastic.
Avoid paper-covered corners. These may look like timesavers, but in actuality do not attach well or provide as good durability as metal ones. You can buy them in varying lengths, or you can cut them with snips to fit.
Measure, Snip, Attach
When covering an outside corner of a wall, you want to purchase enough drywall taping metal corners to cover the entire corner. It is smart to go ahead and measure all the outside corners you will be covering and then buying not only that much, but a little extra, just in case some of it becomes bent or unusable for some reason.
Using screws long enough to go through the drywall taping metal corner, the drywall itself, and then into the wood frame support (1 to 1½”), countersink them with your drill every five to six inches. Run your mud knife down the corner after screwing in the corner to make sure none of them are sticking out.
If so, re-set the screw(s) so that when you run the knife down the corner, none of them hang on any screws jutting out from the reinforcing corner bead. The purpose of this is ensure a smooth, even surface on which to apply the joint compound. Dimpling from countersunk screws can be filled in, but screw heads jutting out cannot.
Applying the Mud
After attaching the drywall taping metal corner, it is now time to apply the mud. Using a wide-blade knife (6 to 10 inches), spread un-thinned joint compound down and along the corner from top to bottom.
Feather the mud out to about four or five inches from the center of the corner reinforcement and fill in any depressions left from the screws. Allow to dry overnight. When thoroughly dry, use your mud knife to knock off any high spots in the mud by running it down the length of the dried joint compound.
Now, apply the second coat of joint compound with a smaller mud knife of 4 1/2″ wide but spread it using the larger knife. By wetting the knife first and following the line of the drywall taping metal corner, the mud should go on smoothly and evenly.
Spread it and feather out about an inch further, six inches from the center of the corner bead. Again, allow it to dry thoroughly, and then apply a third and fourth application following the same procedures, feathering each subsequent coat of mud about an inch or so further out away from the center of the corner.
After the final application of joint compound has dried, use a sanding block with fine-grit (220-grit) to lightly go over the entire drywall taping metal corner. Vacuum away any dust. To finish, touch up any small dents, scratches, or other minor imperfections that may be present with small amounts of joint compound, as needed, using the smaller knife. Allow to dry, sand, and you are done.