How to Apply Joint Compound to Drywall Corners

Drywall panels give your walls a smooth look, suitable for painting or for hanging wallpaper. During installation, the panels are cut and attached to the studs used to frame the walls. You must apply joint compound to the seams to cover them. A standard room has four inside corners, and if the room has a custom configuration, it may contain one, or more, outside corners. Applying joint compound to corners isn't difficult, but you'll need a few drywall tools and supplies to make the process go smoothly.

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Things You'll Need

  • Drywall joint compound
  • Outside corner bead
  • Drywall flex tape
  • 6-inch taping knife
  • 10-inch taping knife
  • Inside corner tool
  • Drywall sander

Inside Corners

  • Apply a layer of drywall joint compound to an inside corner with a 6-inch taping knife. Scoop up about ½-cup of compound at a time and smooth it evenly into the corner, extending it out about 4-inches on both sides.

  • Cut a strip of drywall flex tape about 2-inches shorter than the wall height and fold it down the middle. Flex tape has a plastic coating and a crease down the middle to give you a uniform corner.

  • Position the flex tape in the corner, on top of the wet joint compound, and with the 6-inch taping knife smooth it securely into place on each edge.

  • Apply more joint compound evenly over the tape with the 6-inch knife.

  • Switch to the inside corner tool and place it at the top of the corner, pulling it straight down to smooth the joint compound into a perfect corner shape. When you reach the middle, stop and place the tool at the bottom of the corner and pull upward.

  • Let the joint compound dry completely, and then sand rough areas. Apply a second coat of drywall compound to the corner and use the corner tool again.

  • Feather out the edges with a 10-inch taping knife, and let the corner dry completely once again, before sanding and painting.

Outside Corners

  • Cut a strip of corner bead, about 2-inches shorter than the height of your wall, and attach it to the outside corner. Corner bead comes in plastic and thin metal and features nail holes so you can attach it to the corner with drywall nails.

  • Spread a thin coat of drywall compound over the corner, using a 6-inch taping knife and smoothing the compound flush with both wall edges. It's okay if small globs of compound remain on the edge of the corner bead, but remove any globs larger than a pea.

  • Feather out the edges of the joint compound with a 10-inch taping knife. Position the blade so about an inch extends over the corner, keeping the rest of the blade flush with the wall. Pull the blade evenly down the wall to smooth the joint compound as thinly as possible. Repeat with the other side of the outside corner, and then let the joint compound dry completely.

  • Sand away dried bits of compound that still remain on the corner and smooth rough patches on the walls.

  • Apply a second thin coat of compound the same way you applied the first coat. Take your time and remove as much excess compound as possible. Sand the final coat smooth, using a drywall sander and you're ready to paint your new wall.

Tips & Warnings

  • You'll get better results by using two or more thin coats of joint compound, instead of one thick coat, because the compound shrinks as it dries.
  • Sand the corners very smooth before applying subsequent coats of joint compound.


  • Photo Credit Jupiterimages/ Images
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