How to finish Inside Drywall Corners


Inside drywall corners are many places in a house’s drywall structure. Knowing how to finish them properly will improve the look of every room in your home. This is something most people don’t notice until they see a poorly finished corner that stands out – in a bad way. Despite the benefits, applying a good finish to an inside corner is often a difficult task that takes practice and patience to perfect, but with the right tools and knowledge, you’ll be able to finish yours like a pro.

Getting Started

It takes three days to finish inside corners – one day to tape and two days to apply additional coats and let dry. You’ll need:

  • Joint compound (also known as Drywall mud)
  • Quickset compound, Sheetrock 20, 45, or 90
  • Paper joint tape
  • Corner trowel or roller and flushers
  • Sander or sandpaper and sanding block
  • 6-inch or smaller joint knife

Step 1: Applying tape

Start by using a joint knife and drywall compound to fill in any gaps between the two walls that make up the corner. If the gaps or damaged board is to large a quickset compound is needed. If the fill is to much drywall mud will not dry. Quicksets dry faster than mud and almost don’t shrink. 20,45 and 90 are common in Canada and the numbers stand for how fast it sets ie Sheetrock 20 in 20 minutes. Next, you’ll apply tape to cover the corner. You should use a piece of tape slightly longer than the length of the corner. If you use paper tape instead of fiberglass-mesh tape, there will be a crease in the tape you can use to fold and fit more easily into the corner. You can also tear the tape at an angle for a better fit at the ceiling, allowing for a tighter fit with no bunching.

Step 2: Remove excess mud

With the joint knife, press the tape on both sides of the corner about every 12 inches to remove the excess mud from underneath. Press hard enough to ensure there are no bubbles or gaps under the tape. Leaving mud under the tape can result in it coming undone over time as the wall expands and contracts. Be careful not to tear the tape, however. If it does tear, smooth over the torn portion again with the knife and some compound. You want the tape to be tight and smooth against the drywall all the way up and down the corner. Let the compound dry overnight.

Step 3: Apply another coat

Use the joint knife to apply another coat of joint compound to both sides of the corner, feathering the outside edges as you go. You want the mud from the second coat to overlap the mud from the first coat. Use the blade of the knife to smooth and blend the mud with the drywall. Let dry overnight again.

Step 4: Apply a third coat

When the second coat has dried, apply a third coat to one side of the corner and trim off any excess mud to smooth the corner from one end to the other, blending with the drywall. Let the first side dry, scrape off any buildup, and repeat for the other side of the corner. Apply the compound coat, smooth with the knife, and let dry.

Step 5: Sand to smooth

Once the final coat has dried, sand it to smooth the surface and feather the edges of the mud into the wall. Be sure you don’t dig into the drywall with the sander. Clear dust from the walls with a damp cloth before priming and painting. You’ve just finished your inside corners like a pro!

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