Cracking, splitting, or separations in drywall seams are not unusual, and at times it may become necessary for you to do a joint repair. If you have the right instructions and tools, you can do this job yourself, rather than paying a professional to do it for you. Here are six steps you can use to repair drywall seams in your home.
Step 1 - Remove Damaged Joint
Using a straightedge and sharp utility knife, align the straightedge at one side of the damaged drywall joint, as close as possible to the outer edge of the damaged joint. Cut along the straightedge, through the seam tape and the drywall paper surface, about 1/8" deep into the plaster. The cut line should be long enough that its highest point is above the top edge of the damage, and its lowest point below the damaged section's bottom edge.
Move the straightedge to the opposite side of the damaged section so there is a space between the two parallel lines. The space should be the same width as your drywall tape. Then, make another vertical cut the same length as the first cut. Insert your chisel's sharp edge under the tape and paper and push it through the plaster until the paper, tape and plaster have been removed between the two vertical cuts and have created a 1/8" channel in the drywall.
Step 2 - Insert Joint Strip
Cut a strip of joint tape to place into the channel. The tape should be at least an inch shorter than the channel. This will avoid having tape ends showing above the surface of the drywall after you've filled the channel. Now, lay the paper into the channel, so it is pressed against the rear surface of the channel.
Step 3 - Apply Joint Compound
Use your joint knife to push the drywall mud into the channel so it covers the joint tape. Work the mud into the channel so it mixes with the powdery plaster and adheres to the sides of the channel. The mud surface should be level with the drywall surface, so there are no depressions in the channel mud.
Step 4 - Add Second Strip of Tape
Cut a second strip of tape and lay it carefully against the channel mud surface. Press the end edge of your joint knife against the drywall sheet and span the channel. Then, draw the knife slowly down the channel, adhering the tape to the mud beneath it. Be careful not to make depressions in the tape or channel mud, or to leave mud ridges that will have to be sanded when the mud is dry.
Step 5 - Add Additional Mud Coats
When the first mud coat is dry, add a second coat. If necessary, allow this coat to dry and add a third.
Step 6 - Finish
When all necessary mud coats have been applied and are dried, sand the repaired area and apply primer and paint.