How to Fix a Bubble in Drywall Tape

When you use paper tape to cover drywall seams, you're almost guaranteed to get at least one bubble. It happens because you didn't slap quite enough drywall joint compound (mud) onto the seam before applying the tape, and because there's nothing to hold it, the tape separates from the joint and forms a bubble. If you use fiberglass mesh tape, you won't have this problem.

Bubbles are something you need to correct before you apply texture and paint because they will be visible on the finished surface. If you wait, the mud might crack a few months down the line, and the repair will involve re-mudding the joint and repainting, which isn't a huge problem, but it's definitely a hassle.

When a bubble appears as you're taping and applying the first coat of mud, you can use this procedure to get rid of it:

1. Make an outline in the fresh mud with the corner of your mudding trowel.
   
   
2. Cut along the outline with a sharp utility knife and then grab a corner of the piece of tape you cut out and lift it away.
   
   
3. If the bubble doesn't extend over the joint, simply cover over the gap with mud. It might form a slight indentation, but that should go away when you apply the second coat. If not, it definitely will when you apply the third.
   
   
4. If the bubble extends across the joint, cut the tape along its entire width on both sides of the bubble and remove the tape. Spread fresh mud on the joint and apply a new piece of tape that overlaps the cut edges by about 1/2 inch. Spread a coat of mud over the new tape, let it dry, and then apply your second and third coats.

Another way to fix a bubble while you're taping is to simply spread more mud underneath the part that has lifted.

If the bubble is close to the edge of the tape, lift that edge and spread joint compound underneath it. Scrape the tape onto the fresh mud to seat it and then apply another coat over it.

If the bubble straddles the seam, make two vertical cuts on either side of the bubble that are slightly longer than the bubble is wide but don't reach the edges of the tape. Make a third cut along the seam that extends to the two vertical lines and then fold back the two halves of the tape. Apply fresh mud to the seam, lay the two halves back in place, scrape them flat, and apply a coat of mud over them.

Sometimes, you don't notice bubbles until the mud has dried and starts to crack, which could be long after you've painted the wall. In that case, the only solution is to cut out the bubble and lay new tape.

1. Chip off the cracked mud using a drywall trowel.
   
   
2. Cut out the section of tape that has bubbled and then wipe down the joint with a damp rag to get rid of small chunks of dried mud that may be left behind.
   
   
3. Spread a fresh coat of mud over the cut-out section and lay new tape on it, overlapping the existing tape by a half inch or more.
   
   
4. Scrape over the new tape to embed it in the mud and then apply two or more coats of fresh mud, letting each coat dry before applying the next.
   
   
5. Sand the repair flat with 120-grit sandpaper and then apply a coat of drywall primer. Touch up the texture and paint when the primer dries.