Taping Inside Corners: Techniques for Clean Results

Published December 28, 2024 by Mike Sullivan

Key Takeaways

  • Paper tape has a factory crease for folding into corners
  • Embed one side completely before moving to the other side
  • Corner tools help but aren't required for good results
  • Inside corners don't need corner bead like outside corners do
  • Let each side dry before coating the adjacent side to prevent pulling tape

Inside corners were my nemesis when I started finishing drywall. The tape wouldn't sit in the corner. The mud bunched up. I'd smooth one side and mess up the other. Every inside corner in my basement looks worse than the flat seams.

Eventually I figured out the technique. Inside corners have a rhythm: work one side, then the other, don't try to do both at once. Once that clicked, corners became routine instead of frustrating.

Why Inside Corners Are Different

Inside corners, where two walls meet or where walls meet ceilings, have two surfaces meeting at an angle. Flat seams only have one surface to worry about. Corners have two, and what you do to one affects the other.

The good news is inside corners don't take the same beating as outside corners. Nobody bumps into an inside corner. They don't need metal corner bead, just tape and mud like flat seams.

The challenge is keeping both sides looking good while working in a tight angle.

Folding the Tape

Paper drywall tape has a factory crease down the center. This isn't a defect. It's designed to fold along that crease for corner installation.

Before applying, fold the tape along the crease so it forms a 90-degree angle. You can fold sections as you go or pre-fold a length before starting.

The folded tape should sit snugly in the corner with equal tape on each side. If it doesn't want to stay in the corner, you might not have enough bed coat in the angle itself.

The Bed Coat

Apply joint compound to both sides of the corner, about 3-4 inches wide on each surface. Make sure to get mud into the actual angle where the walls meet. This is where the tape needs to bond.

Consistency matters here. Too thick and you can't seat the tape. Too thin and there's nothing for the tape to grab. Aim for about 1/8 inch thickness.

If your corner isn't perfectly straight, the bed coat is where you can start building it out. Apply slightly more mud where the corner is low, less where it's high.

Embedding the Tape

Press the folded tape into the corner, starting from one end. The fold should sit right in the angle.

Here's the technique that changed everything for me: embed one side at a time. Run your knife down one side of the corner to press that half of the tape into the mud. Don't worry about the other side yet.

Then run your knife down the other side. Working one side at a time prevents pulling tape off the first side while working the second.

Apply firm pressure but don't scrape so hard that you pull the tape out of the corner. You want mud to squeeze out from under the tape, but the tape should stay seated in the angle.

Corner Tools

Specialty corner tools can speed up the process for people who do a lot of drywall. The most common is the corner trowel, an angled knife that works both sides of the corner simultaneously.

Pros: Faster once you're skilled. Creates consistent angles. Less chance of pulling tape during embedding.

Cons: Learning curve. Not worth buying for small jobs. Can't adjust for out-of-square corners.

I own a corner trowel but often don't use it. For a bathroom or bedroom, regular knives are fine. For a whole house, the corner tools start to pay off.

Finishing Coats

After the tape is embedded and the first coat is dry, apply finish coats to build out and smooth the corner.

The key: work one side at a time and let it dry before doing the adjacent side. Trying to work both sides while wet risks pulling freshly applied mud with your knife on the return stroke.

First side: apply mud, feather it out 6-8 inches from the corner, smooth. Let dry overnight.

Second side: repeat on the opposite surface. Let dry.

Third coat if needed: same process, feathering slightly wider for smooth transitions.

This alternating approach takes longer but produces clean corners without the frustration of constantly messing up one side while working the other.

Common Corner Mistakes

Problems I've had:

Working both sides at once. The knife on the second side catches the first side and pulls it. Work one side, let dry, then the other.

Not enough bed coat in the actual corner. If the angle is starved for mud, the tape won't bond there. Make sure mud gets into the angle, not just on the flats.

Forgetting the tape fold. The factory crease exists for a reason. Tape that isn't pre-folded fights you the whole way.

Aggressive sanding. Corner sanding should be gentle. Sand through the tape in a corner and you've got a bigger problem than a visible seam.

Using mesh tape. Mesh tape can work in corners but it's more likely to crack because it's weaker in tension. Paper tape holds up better.