Inside corners are more difficult. They require taping and mudding. The hard part is smoothing the mud on one side of the corner without messing up the mud on the other side. Resist the temptation to try to get these inside joints perfect on the first, or even second, coat. Accept that there will be ridges you’ll need to sand or knock off in the first two coats. To avoid ridges on the third coat, think of it as a filler coat; press hard on the knife so you fill imperfections instead of leaving behind a thick layer of joint compound. Go over the joints a fourth time if necessary for a smooth finish.
What You Need
MudPaper tape6-inch knifeInside corner toolSandpaper
Step 1: Apply Mud
Apply mud to both sides of the corner. Fold a length of paper tape in half (it is precreased) and press it into the mud with a 6-inch knife. An inside corner tool embeds the tape and smoothes the joint on both sides at the same time. Editor’s Tip: If you’re a beginner, you’ll probably find that composite drywall tape will give you much faster and better results than paper tape at inside corners. You simply unroll the length you need, cut it with a knife, and fold it down the middle. Embedding is similar to working with paper tape, but the next coats are much easier because the stiff material creates a sharp inside corner. So instead of shaping the corner, you simply feather the compound away from it until you’ve concealed the tape’s edges.
Step 2: Repeat and Sand
Embed the tape in the mud by drawing down the knife along both sides of the corner. Repeat this process to apply additional coats of mud. Sand to smooth the final surface.
How to Fix Bubbles Under the Paper Tape
If there are bubbles under the tape, the tape doesn’t stick to the mud, or it wrinkles, peel it off and apply more mud underneath. This is one time when applying a little too much mud is not a problem.
Bonus: Different Corner Framing Methods
Wall construction involves inside/outside corners as well as T-walls. The drawings present strategies for framing these junctions in both wood and steel. If you choose the assembly shown in the T-wall drawing, the blocking can be a full-length stud or you can substitute short pieces of stud material, a strategy that saves money and also helps scraps disappear. If you’re attaching your new wall to an outside wall, insulate any cavities between the blocking before attaching the second wall.
