How to Finish Drywall Seams

Once drywall is hung, the seams between boards must be finished before work on the walls can continue.

Finishing drywall correctly is a vital step in obtaining a smooth-looking surface suitable for plaster, tiling or painting. Handling the seams between drywall boards is a large part of the finishing process. Badly finished seams stick out, giving your walls a blotchy, patterned rough look, while well-finished seams not only make the drywall unnoticeable, but make material application to the drywall easier. Taping the seams is the most commonly used finishing technique, requiring a few short steps to quickly cover the seams in an entire room.

Things You'll Need

• Joint compound
• Paper wallboard tape
• 5-inch taping knife
• 80-grit sandpaper
• 10-inch joint finishing knife
• 120-grit sandpaper
• 8-inch joint finishing knife

Instructions

1. Mix a batch of joint compound in a bucket, taking care not to whip air into the compound. That can create bubbles when the compound is applied.

2. Spread a layer of the compound onto the seams, beginning at the ceiling and working your way downward. Use a 5-inch taping knife to spread the compound evenly over seams. Fill the seam with the joint compound completely, and slightly overfill the seam so that there's a slight ridge of compound at the points where the boards meet.

3. Place the joint tape over the seam beginning at a corner and press the end of the tape lightly into the corner until it sticks. Apply the tape centered onto the seam over the joint compound until the seam is covered. Cut the tape, using the utility knife when the end of the seam is reached.

4. Go over the placed tape with the taping knife, pressing it firmly over the seam. Begin at the center of the seam working toward the ends, pressing the tape flat and spreading the ridge of the compound along the back of the tape.

5. Spread a thin layer of the compound onto the top of the tape, covering the surface of the tape and about 1/4 inch to the tape sides to cover the tape edge. Make the layer as thin as possible; the tape beneath should remain visible. Allow the seam to dry completely for the length of time suggested by the compound manufacturer.

6. Sand the surface of the tape with 80-grit sandpaper to level the compound with the surface of the wall.

7. Apply an additional layer of compound to the seam. Smooth it off with a 10-inch joint finishing knife so that the layer ends about 2 inches beyond the edges of the first coat. Allow the compound to dry for 24 hours.

8. Sand the compound with 120-grit sandpaper to smooth the surface.

9. Mix a batch of compound, adding a few drops of water to the mixture to create a smoother compound. Apply the thinned compound to the seam to level it with the wall. Smooth the compound off with an 8-inch joint finishing knife, adding 2 more inches to the width of the coverage area. Allow the compound to dry for 24 hours.

10. Sand with 120-grit sandpaper to create a flat, smooth seam.

Tips & Warnings

• Always keep the knives clean by scraping them against the bucket to prevent the compound from drying on the knife edge and ruining the compound application.

References

• Hometime How-To: Finishing Drywall Joints: Tape Coat
• Bob Vila: How to Tape and Finish Drywall Seams
• Ask The Builder: Ten Secret Drywall Finishing Tips

Resources

• Hometime How-To: Drywall Tools
• Hometime How-To: Types of Drywall