Tape a Drywall Crack or Flat Seam
Category: Drywall ·
Difficulty: Beginner ·
Time: 1.6h ·
Estimated cost: $27
Tools needed
- 6" taping knife
- 12" taping knife
- Mud pan
- Utility knife
- Sanding sponge (220 grit)
- Raking work light
Materials needed
- All-purpose joint compound (quart) (1 qt)
- Paper joint tape (250 ft) (1 roll)
- Drywall primer/PVA (quart) (1 qt)
- Wall paint to match (quart) (1 qt)
Execution steps
Clean and undercut the crack
Scrape off loose paint and old compound. For a recurring crack, run a utility knife down it to slightly widen and undercut a shallow V so fresh mud keys INTO the crack instead of just sitting on top.
Duration: 10 min
Bed coat + paper tape
Mesh is weak on flat seams — use PAPER tape here. Lay a thin bed of all-purpose mud over the crack, press the tape into it, and pull a 6" knife down the tape to squeeze out excess, leaving mud UNDER the tape (not none).
Duration: 20 min
First fill coat
Once the bed coat is fully dry, apply a coat over the tape with the 6" knife and feather the edges. Don't rush drying — wet mud under a top coat cracks.
Duration: 15 min
Second / finish coat
Skim a wider coat with the 12" knife, feathering 2-3" past the previous coat. Two thin coats beat one thick one.
Duration: 15 min
Sand flat
Knock down ridges with a 220 sanding sponge, holding a work light flat against the wall (raking light) so you catch high spots before paint does. Wipe dust with a damp sponge instead of dry-sanding.
Duration: 15 min
Prime and paint
Seal the bare mud with drywall primer/PVA or it will 'flash' (dull spots), then roll two thin coats of matching paint, feathering into the surrounding wall.
Duration: 20 min
Safety first
- Wear a dust mask when sanding — gypsum dust irritates the lungs.
- Use a sturdy ladder for ceiling seams and keep your hips inside the rails.
When to hire a pro
A crack that keeps coming back at the same spot can mean structural movement or truss uplift — have a pro diagnose the cause before you keep re-mudding it.
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