Let inside drywall corners move

Myron R. Ferguson (www.thatdrywallguy.com), author of Drywall (The Taunton Press, 2008), replies: Cracks in inside corners often indicate structural movement. This movement might be caused by swelling or shrinking of framing lumber due to seasonal changes, or it might indicate a more significant structural problem. If you’ve eliminated the latter possibility, there are some things you can do to fix the cracks.

Vinyl or PVC tapes made for seams and inside corners are strong, but they often pop loose if there is structural movement. Don’t use these products unless you’re sure the corner is stable.

In situations like yours, you’ll have the most success in making a joint resistant to cracking by letting it move. The only thing I have found that works is an expansion-joint type product. I have had great success with Magic Corner from Trim-Tex (www.trim-tex.com). It works on inside corners at any angle, and it also can be used to fix cracks.

To repair an inside corner, fully remove the existing tape, and replace it with Magic Corner. Tape the joint as you normally would, leaving the rubber center free of mud. Any movement will be absorbed by the rubber center, which flexes and stretches. The only bad thing is that you see the rubber center as a slight recess in the surface. This slightly indented line is much better than a crack.

A flexible center joint absorbs seasonal movement. An expansion-joint-type product like Magic Corner is the ideal fix for inside drywall corners that crack due to seasonal movement. Photo by: Krysta S. Doerfler

Install the joint with spray adhesive and staples. The joint can be painted per the manufacturer’s instructions. Photo by: Krysta S. Doerfler