How to tape and mud drywall

Choosing tape and compound

Paper tape is the standard for seams and inside corners: it is stronger and resists cracking. Fibreglass mesh tape is self-adhesive and quicker, and works well for patches, but on seams it should be covered with setting-type compound, not premixed, or it is prone to cracking.

Tools you need

• 6-inch, 10-inch and 12-inch taping knives, and a mud pan
• An inside-corner tool (optional, but it helps)
• A utility knife for trimming tape and paper
• A pole sander or sanding sponge, and a bright work light
• A dust mask. Joint compound dust is fine and gets everywhere.

Taping flat seams

1. Fill any gaps wider than about ⅛ inch with setting-type compound first and let it set.
2. Spread a smooth bed of compound along the seam, about as wide as your 6-inch knife.
3. Press paper tape into the wet compound, centered on the seam, and pull the knife along it at a low angle to squeeze out excess. No dry spots under the tape; that is what causes bubbles.
4. Skim a very thin layer over the tape right away, or wait for the next coat.
5. Let it dry fully before the next coat.

Second and third coats

1. Scrape off ridges and lumps with a dry knife before each coat. Do not sand between coats unless you have to.
2. Second coat: use a 10-inch knife and feather the compound a few inches past the edges of the first coat.
3. Third coat: use a 12-inch knife and go wider and thinner again. On butt joints, where two uncut ends meet, feather out 16 to 20 inches so the joint does not show as a hump.
4. Cover every screw head with three coats as well, each slightly wider.

Inside and outside corners

Inside corners use paper tape folded along its centre crease. Coat both sides of the corner, press the folded tape in, and smooth one side at a time; working both at once drags the other side. Outside corners get corner bead, metal or paper-faced, fastened on, then three coats feathered out from the bead onto each wall.

Sanding and priming

Sand lightly with fine grit, just enough to remove ridges and tool marks; heavy sanding scuffs the drywall paper and shows under paint. Shine a work light flat along the wall to find what needs another skim. Then prime everything with a drywall primer before texture or paint. Bare compound and bare paper absorb paint differently, and unprimed walls show the joints.

Common mistakes

• Thick coats. They take longer to dry, crack and shrink. Thin coats, three times.
• Dry spots under tape. Tape bedded in too little compound bubbles or peels later.
• Narrow feathering. Joints finished too narrow show as ridges under paint.
• Rushing the drying. A coat over damp compound traps moisture and can crack.
• Skipping primer.

What it costs to hire out

See drywall installation cost for full pricing, or how to fix a hole in drywall for patches.