How To Repair Loose Drywall Tape

How to Repair Drywall Tape That Is Separating from Your Walls

You are best off taking down the pealing tape and installing new tape, but here is how. You will need drywall tape and spackle.

Steps
Tear tape from wall.

Fill area where tape was with a plentiful smooth layer of spackle.

Place tape over spackle and use spackle blade to smooth the tape over it. Make the tape a little below the wall surface.
Let dry.

Spackle over the tape and make area smooth with surface of the wall.

Paint wall with color to match,be sure to use primer first on area or spackle will show through.

Tips
Use clean tools for smoother walls.
Using color changing (pink to white when dry) spackle will help you to know when the spackle is dry, but wait five minutes after the spackle is white.
Have patience for spackle to dry.
If there is a very small separation of the tape from the wall, put a small amount of caulk or white glue behind the tape and press it back in place.
Also, you can use 'All Purpose' tape and joint compound henceforth called 'Mud' for larger problems, since spackle does not have much if any stick to it and actually would not advise accept for small touchup. See Patch A Wall.
If tape is bubbled, can puncture and slit with razor blade knife, and slip joint compound into the slit under the tape and press hard to wall. Cover the slit with mud or spackle. Use narrow one inch spackle blade. Always use paper tape as mesh often cracks. To repair cracked mesh tape, tape over with paper tape and mud.
If tape is only loose on one side can slip a putty knife under it to loosen, then slip tape and joint compound under entire piece of loose tape, then press hard to wall. Can cover crack with mud or spackle.
If entire piece of tape is loose, and can pull back what is loose without breaking it; put joint compound in track and press tape back to wall. Can cover with mud or not or use spackle.
When removing tape altogether, cut out and pull out loose tape. Apply mud compound and press in new piece of tape directly into the old track. Thoroughly wetted tape, even overnight will go in thinner. Cover with mud, one or two coats.
Metal corner bead when edges are not taped may crack. Tape and mud cracks. Paper edged corner bead which is not screwed, but only mudded in, may crack and pull loose. Paper tape over.
Tape and joint compound, All Purpose and or Topping can be either sanded or sponged when dry. Sanding does the best finish, but sponging is adequate under flat latex and where dust is a consideration. Primer is generally not needed unless a good hard skin is required, if a lot of paint is used like with a roller and or two coats are used.

Warnings
Test paint on a small area of your wall to make sure the color will match. If you need new paint match a paint chip to your wall and bring it to your local paint store to have the color matched.
Wait for spackle to dry.
Check for underlying causes of loose tape such as moisture intrusion or loose sheetrock. Moisture generally shows a stain but a moisture meter is more accurate. Loose sheetrock can rattle when you slap the wall firmly with an open hand. If either of these problems exist, fix them before bothering with the tape repair/replace.