How do I fill holes in a wall?
How to fill screw holes, dents and larger holes in plasterboard or plaster so the repair genuinely disappears under paint.
- Difficulty
- beginner
- Time
- 40 min
- Read
- 3 min
Short answer
Clean out the hole, apply filler slightly proud of the surface with a flexible knife, let it dry fully, then sand flush with fine paper. Holes bigger than about 30mm need backing — a patch or mesh — because filler alone has nothing to hold on to.
The reason amateur filling shows through paint is almost never the filler. It's that the repair is either proud of the wall, or sanded into a shallow crater around the hole, and paint makes both obvious under raking light. The technique below is really about controlling the surface level and giving the filler something to grip.
What you'll need
- Ready-mixed or powder filler
- Flexible filling knife (50mm and 100mm)
- Fine sandpaper (120 and 180 grit)
- Damp cloth
- Self-adhesive mesh patch for larger holes (optional)
- Dust sheet (optional)
Step by step
- Scrape out loose material and any raised edges around the hole.Filler bonded to a loose flake will fall out with the flake. Undercut slightly if you can — a hole wider inside than out holds the filler mechanically.
- Brush out dust and wipe with a barely damp cloth.Dust is a release agent. A dusty hole is the most common cause of filler popping out later.
- Press filler firmly into the hole with the knife, working it in rather than skimming it over.Air pockets behind the surface collapse when you sand.
- Leave it slightly proud of the wall — about a millimetre.All fillers shrink slightly as they dry. Level now means slightly hollow tomorrow.
- For holes over about 30mm, fit a self-adhesive mesh patch first, then fill over it in two thin coats.Filler has no strength across a void. The mesh is what stops it cracking out.
- Let it dry completely — usually a few hours, longer for deep fills.Sanding damp filler drags it out of the hole and clogs the paper instantly.
- Sand flush with 120 grit, then finish with 180, keeping the block flat against the wall.Flat block, light pressure, wide circles. Sanding with a fingertip digs a dish around the repair.
- Wipe off dust and spot-prime the repair before painting.Filler is more absorbent than the surrounding wall — unprimed, it shows as a dull patch through the topcoat.
Tips
- Two thin coats beat one thick one every time: thick filler shrinks, cracks and takes all day to dry.
- For a very small hole, a light smear applied with a fingertip and wiped back with a damp cloth needs no sanding at all.
- Run your hand over the dry repair with your eyes shut. You will feel a ridge you cannot see, and so will the paint.
- Deep holes in solid plaster are better filled in layers, letting each dry, than in one go.
Common mistakes
- Filling level with the wall — Shrinkage leaves a visible dip once painted.
- Skipping the spot prime — The porous filler absorbs paint differently and flashes as a matt patch.
- Sanding too hard around the repair — You dish the surrounding plaster, which is more visible than the original hole.
- Filling a large hole without backing — There's nothing behind it — the filler cracks and drops out within weeks.
Questions people ask
What's the best filler?
Ready-mixed lightweight filler for small holes, because it sands easily and doesn't shrink much. Powder filler mixed thick is better for deep holes and for anything that needs strength.
How long before I can paint?
Follow the tub, but as a rule small fills are ready in two to four hours and deep ones need overnight. Painting over damp filler traps moisture and the patch shows.
Can I fill a hole in plasterboard where the screw pulled through?
Yes, but don't just fill it — the plasterboard around it is crumbled. Use a mesh patch or a plasterboard repair plug, then fill over it, and put the new fixing somewhere else.