How to Finish Inside and Outside Drywall Corners Like a Pro

Drywall is liked by a lot of people; not only does it make a great final product, but it is also cheap and easy to work with. Still, don’t get “simple” and “easy” mixed up. After all, they are drywall experts for a reason: getting the best results takes practice and a steady hand. Finishing the drywall corner is, without a doubt, the hardest part of drywall work to get right.

This is especially true for corners, where you have to blend not only different sheets of drywall but also different surfaces together. At first, it can be hard, but it’s the key to making beautiful things. This guide will cover everything you need to know to make inside and outside corners look great.

Finishing Drywall Inside Corner Joints

For the wallboard joints at the inside corners, you will use a corner trowel tool; there is no need for a mud pan. Just dip the corner trowel right into the joint compound bucket and coat the corner joint well.

Step 1

Start at the top of the wall and press the compound into the corner, holding the blade at a low angle to the wall. Work your way down to about the center, then start at the bottom and work your way up. Working this way lets you avoid ending up with a big glob of the compound on the floor. You want to get the compound pressed into the nailhead dimples and the gap between the adjacent drywall sheets.

Step 2

Cut a length of joint tape that will cover the entire corner joint. Slowly fold the tape in half along its length, being careful to fold it evenly. Align the center of the fold in the tape with the joint, and cautiously press your tape into the corner joint. Do not squeeze all of the joint compounds out from underneath the tape, but press it well into the joint. Be sure the tape sticks to the wallboard.

Step 3

Bury the joint tape in the compound by coating it as in step 1. You should not see the tape when this step is done, but at the same time, you should not have so much compound in the joint that it will crack when drying. Remove the excess at the edges with the 6-inch compound knife.

Step 4

Repeat the above steps for the joints between the walls and ceiling wallboard.

Finishing Outside Corner Drywall Joints

Now on to the outside drywall corner..

Step 1

The outside corner joints of a room are actually the easiest to finish, especially if you use a metal bead strip. Cut a strip of corner bead long enough to cover the whole corner from top to bottom. Fold the strip in half along the crease and fasten it to the wallboards about every six inches with screws.

Run your 10-inch finish knife down the corner, using it like a straight edge, in order to ensure the screw heads do not protrude above the wallboard surface. If any screws hit the knife edge, tighten the screw down more or install more screws in the bead.

Step 2

Apply joint compound liberally to the corner, filling in the valley from the corner 4 to 5 inches in from the corner on both walls. Use the metal bead as a guide to level the compound with a 10-inch knife held perpendicular to the wall. Any leftover compound should be used to fill screw dimples. Throw the rest away, then thoroughly wash your tools. Now allow the joint compound to dry for 24 hours.

Step 3

Use a 4.5-inch knife to apply a second coat of compound about 6 inches wide to each side of your outside corner joint. Level it out with the 10-inch knife once again, using the metal corner to guide you. If you wet the knife down first, it will smooth better and have less tendency to leave behind a wavy effect. Any leftover compound should be used to fill screw dimples. Throw the rest away, then thoroughly wash your tools. Allow the compound to dry completely.

Step 4

After all the mud is thoroughly dry, run your (dry) 10-inch knife down each side of the corner and knock off any mud that blocks its path, as done in Step 3. You are ready for another coat if the knife hits no more high spots.

Step 5

Repeat step 3, except make this third coat about 8 inches wide on either side of the corner. Allow to completely dry; then knock off any excess mud by running a clean, dry 10-inch knife down each side of the corner.

Step 6

Repeat step 5, except make this fourth coat about 9.5 inches wide on each corner side, using a slightly thinned joint compound. The corner should now be almost finished.

Step 7

After the fourth coat is dry, fill in any wavy drag marks by applying a small portion of thinned compound to the imperfection. With the 4.5-inch knife, carefully level it off. Draw the knife perpendicular to the direction of the drag marks, keeping pressure steady on the knife.

Step 8

Lightly sand the dried compound with 220-grit sandpaper on a sanding block. Vacuum the area of any dust. Stay away from sanding the paper surface of the wallboard, as it will leave frayed fibers that look bad even after painting. The corner should now be ready to prime with a good latex primer.

Final Words

Inside and outside corners are a common part of a house’s drywall structure, and if you know how to finish them right, you can make every room look much better. Most people don’t notice this until they see a corner that isn’t finished well and stands out in a bad way. Even though there are benefits, giving an inside corner a good finish is often hard and takes time to get right. You can finish your drywall corner like a pro with the right tools and knowledge.

Author Aaron Walker

Written by: Aaron Walker

I have extensive construction knowledge and I always stay up to date on current events and new technologies and hope to share my knowledge and expertise here. I am focused on green technologies and home improvements that include green living ideas.