DIY Finishing Drywall Seams

• Installing Corner Bead
• Finishing Inside Corners
• Skim Coating Techniques
• Sanding Joint Compound

This page contains taping and finishing instructions for flat drywall seams. Go to Installing Drywall Corner Bead and Finishing Inside Corners for help with those projects.

Flat drywall seams can be finished with paper tape or self–sticking, fiberglass mesh tape. Always use ready–mixed joint compound for finishing drywall seams. Setting–type joint compound will harden too quickly, causing problems. See Wall Finishing Tools and Materials for more information about drywall finishing tools, tapes and joint compounds.

Tape and First Mud Coat

Drywall sheets are compressed on two finished edges so when two sheets are placed edge to edge, a small depression is formed. The seam between the sheets is taped with drywall tape and the depression is filled with drywall joint compound or mud, to create a smooth finished surface.

Cut a piece of paper drywall tape a little longer than the length of each joint. Cut the ends squarely so they will form a good joint at ceiling and wall corners. If you're using fiberglass mesh, tape all the flat joints you will be finishing at the same time. Butt the end of the tape squarely at the corners and cut it off squarely at the other end.

Scoop mud into a mud pan and collect a portion onto the rim. From the rim, work the mud onto the wall, a little at a time. See Skim Coating Techniques for more on handling joint compound.

When using paper tape, apply a coat of mud about ½in thick over the joint with crossing strokes. Lightly press the tape into the mud starting at one end of the seam. Work to the other end pressing gently with two or three fingers to avoid squeezing the mud out. Pull the tape firmly to keep it as flat as possible. Leave the last couple of inches loose until the end.

Hold a 6 inch joint knife at about a 30° angle. Start a few inches from the first end and draw the knife along, pressing hard against the tape to squeeze out all but a thin coat of mud from between the wall and paper.

Skim back in the opposite direction to finish the end and then work down the seam to the other end. Return the excess mud to the rim of the pan as it collects on the knife blade. At the other end of the seam, pull the tape firmly while skimming out the remaining mud. While still holding the end of the tape press the sharp edge of the joint knife into the corner and pull out on the tape to cut it off squarely at corner. Go back over the edges to skim off any mud buildup there.

If you are using fiberglass mesh tape, apply a thick coat of mud over the taped joints using crossing strokes. Cover the tape and fill the depression to overflowing with excess mud. Work on about 6 feet of the seam at a time or from ceiling to floor when working on walls. Skim the excess mud from the mesh tape. Hold the joint knife at about a 30 degree angle, press down firmly while drawing the blade along the tape to remove the excess mud. Avoid using too much pressure that would dig into the fibers of the tape. Leave a thin coat of mud over the tape. Skim the excess mud from the edges and surrounding wall. Return the excess mud to the rim of the pan after each stroke of the knife to keep the blade clean.

When all the joints have been skimmed return the unused mud to the joint compound bucket and wait at least an hour before applying another coat.

Finishing Mud Coats

Apply a second coat of mud to the seams when the first has set firmly. Fill the pan with mud and apply a thick coat over the joints. Use crossing strokes to cover the tape and fill the depression between the drywall sheets with excess mud.

Skim the excess mud from the seam using a 10 inch joint knife. Rest the knife on the high point along each side of the depression and "float" the blade over the center of the seam. Try to leave a thick coat of mud in the depression and level it with the surrounding wall. Don't press too hard on the center of the 10 inch blade. This will cause it to bow and create a perceptible dip in the finished seam.

Be sure to skim off all excess mud along the edges of the joint as well as the center. Allow the mud to dry for a couple of hours and repeat this step as many times as needed to completely cover the tape and fill the depression. Check for a good finish by holding the joint knife perpendicular to the wall surface and look for any gap indicating the depression is not quite level. Let the final coat of mud dry for 6 to 12 hours and lightly sand with medium grit sandpaper to finish the job.