DIY Drywall Finishing Inside Corners

Use Ready–Mixed Joint Compound

Use ready–mixed joint compound or mud for this job, setting–type joint compound will harden too quickly, causing problems. See Drywall Finishing Tools and Materials for more information about drywall finishing tools, tapes and joint compounds.

Fold Paper Drywall Tape

Finish inside drywall corners using paper drywall tape, not fiberglass mesh. Cut the tape, squarely, a little longer than the corner to be finished and fold it along the center crease.

Apply Mud to the Corner

Use a joint knife and mud pan to apply a thick coat of joint compound to both walls, along the whole length of the corner.

Set the Tape

Start at one end of the corner and place the folded paper tape into the mud. Open the tape and gently press it down so it makes contact with both surfaces. At the end of the corner cut the excess tape to the proper length.

Skim the Mud

Use a small joint knife to skim one wall at a time. Hold the joint knife at about 30° and skim along the tape to press it down and remove the excess mud. Scrape the knife blade on the mud pan frequently to keep it clean.

Skim Again

To insure the tape won't come loose over time, go over it again, pressing harder with the blade, to squeeze all the excess mud from between the tape and drywall. If there is too much mud under the tape it can cause it to pop free with normal expansion and contraction in the wall.

Be careful not to tear the tape with repeated strokes. If the tape bunches up or tears, straighten it out and smooth it again with the knife and a little joint compound if necessary. Before moving on, be sure the tape is tight and smooth against the drywall.

Apply a Second Coat

Allow the mud to dry completely and apply a second, thick coat to both walls.

Skim the Second Coat

Skim the excess mud from the corner using the same technique as the first coat. Don't be concerned that the mud doesn't come together at the corner in a perfectly smooth finish. The edge of the knife blade will ruffle the point where the two planes meet, this will be corrected in the next step.

Finish Coat

Let the second coat sit for several hours or overnight, until it's completely dry. Use the joint knife to scrape any dry, rough compound from the corner and then apply a thick coat of mud to one wall. Immediately skim off the excess mud to smooth out the finish and let it dry.

Use the joint knife to scrape off any buildup of dry mud in the corner and then apply a thick coat of compound to remaining wall. Immediately skim off the excess as before and let it dry.

When the mud is completely dry lightly sand with 120 grit medium sandpaper to smooth the surface and feather the edges into the surrounding wall. Wipe the dust from the walls with a damp cloth before priming and painting. Use one coat of drywall primer if you are using flat latex finish paint. If you are using semi-gloss or other shiny paint, prime with 2 coats of latex primer.