While the skill of perfect finishing comes only through practice, there are several common issues that are easily corrected with a better technique or materials, or both.
Watch Now: How to Properly Finish Drywall
Inside Corners Look Ragged
Instead of creasing the all-paper tape that you might be used to, try metal-reinforced corner tape.
Metal-reinforced tape combines a metal angle with paper flanges for a perfectly shaped and smooth inside corner: the tape does the creasing for you. The metal also gives your drywall knife a smooth, rigid surface to ride along when taping the corner.
Outside Corners Are Rough or Fragile
Instead of using standard paper tape on outside corners, use metal or plastic outside corner bead.
The best practice is to use corner bead because it is more durable and easier to install than paper-only corners. Save the paper tape for outside corners that never receive any traffic, such as bulkheads or skylight shafts. Any outside corner within reach should use a rigid bead.
Mud Dries Before Paper Tape Goes On
It's common to apply the drywall mud to the wall, then find that the paper tape isn't sticking well because the mud has dried.
Before you apply the joint compound or mud, cut your paper tape to length and pre-crease it. You'll save yourself a crucial few seconds.
If you're using metal-reinforced tape, cut it to length and have it at the ready before mudding the corner. In either case, it's also easier to measure for your tape length before there's mud on the wall.
Drywall Tape Shows Through the Mud
If you keep seeing the drywall tape under the mud, your coating is too thin.
Use three layers: tape coat, filler coat, and final coat. The tape actually should show through the filler coat. If it doesn't, your filler coat is too thick. Covering the tape comes only with the final coat or coats. If your initial final coat doesn't cover the tape, apply more coats, but keep them thin.
Mesh Tape Showing Through Butt Joints
This can be hard to fix and it's why a lot of drywall workers prefer paper tape on butt joints. Butt joints are seams where two panels meet at their square (not tapered) edges, so there's no recess for the tape and mud.
If you've already used mesh tape and mudded over it and it's still showing, keep applying thin final coats with a 10- or 12-inch drywall knife. Gradually build up the joint in the middle—to cover the tape—and feather it at both sides to make it all look flat.
Paper Tape Visible on Butt Joints
Butt joints are difficult to cover, even with paper tape. Since you have no edge tapers creating a recess, the tape and mud are riding on top of the drywall.
Carefully apply the final coat or coats and feather it out well with the 10- or 12-inch knife. One error with butt joints is to use too much mud under the tape, creating a hump that is hard to hide with all of the thin final coats.
Applying some pressure to the knife when smoothing the tape over the initial layer of mud helps to squeeze out excess mud from behind the tape. Ideally, though, don't put too much mud there to begin with.
Drywall Seams Cracking
Drywall joints crack for many different reasons. Over the door and window openings, joints can crack due to movement in the wall framing. The movement is unavoidable, so the best solution is to make the taped joints as strong as possible.
The paper tape itself is less strong than mesh tape, and paper is also less elastic and doesn't stretch as mesh tape does. This is why some drywallers prefer paper for these high-stress joints.
If you do decide to use mesh tape in these areas, always use a setting-type mud for the first coat over the tape. Setting mud is stronger than pre-mixed all-purpose mud and helps compensate for the elasticity of mesh tape.
Any drywall joint can also crack if the mud is applied too thick or too quickly. To prevent cracking, don't use more mud than you need for any of the coats, and let each coat dry completely before adding the next.