- Ready-mix filler (Polycell or similar) — good for most holes up to about 10mm
- Filling knife or putty knife (a wide, flexible blade)
- Sandpaper — medium grit (80–120) and fine grit (180–240)
- Damp cloth or sponge
- Mist coat or stain-block primer
- Paint to match your wall
Step 1: Prepare the hole
Before any filler goes in, the hole needs to be clean and solid. Loose or crumbling plaster around the edge won’t hold filler — it’ll just pop out later. Use your finger or a screwdriver to remove any loose bits, then blow out any dust.
If the hole has a rawlplug or anchor in it, pull it out first. If you can’t, push it all the way into the wall so the filler can go on top.
Step 2: Dampen the area
Lightly dampen the inside of the hole and the surrounding plaster with a wet finger or damp cloth. This stops the wall sucking moisture out of the filler too fast before it can bond properly — especially important on bare plaster or porous brickwork.
Step 3: Apply the filler
Load a small amount of filler onto your filling knife and push it firmly into the hole, pressing all the way to the back. Work it in rather than just spreading it over the surface. Then draw the knife across the hole to leave the filler slightly proud of the wall — not flat, but just a hair above the surface. It will shrink as it dries.
Don’t fill in one go — it’ll crack as the outside dries before the inside. Do it in two or three layers, letting each one dry fully before adding the next. Build up to just below the surface, then do a thin final coat to finish flush.
For very large holes (say, a fist-sized chunk of plaster), push a piece of mesh repair tape or cardboard into the hole first to give the filler something to key into.
Step 4: Let it dry fully
This is the step most people rush and regret. Filler needs to be completely dry before you sand it. Ready-mix filler goes white when it’s dry — if any part is still grey or darker, it’s not ready. Drying time depends on:
- Thickness of the fill — thin coats: 1–2 hours; thicker fills: 4–6 hours
- Room temperature and ventilation — warm and airy dries faster
- Type of filler — lightweight and quick-dry products set faster than standard
Step 5: Sand flush
Once bone dry, sand the filler back level with the wall. Start with medium grit (80–120) to knock back the proud section, then finish with fine grit (180–240) to get a smooth surface. Run your finger across the filled area — you should feel no ridge or bump against the surrounding wall.
Wipe away all the dust with a slightly damp cloth and let the surface dry completely before painting.
Step 6: Prime before you paint (don’t skip this)
This is the most commonly skipped step — and the one that causes the “you can see where I filled it” problem. Filler is porous. When you paint directly over it, the filler soaks the paint in differently to the surrounding wall, leaving a dull or shiny patch that’s visible even after two coats.
Apply a thin coat of mist coat (water-diluted emulsion) or a stain-block primer to the filled area. Let it dry, then paint the whole wall normally. The filled patch will blend in completely.
- Painting over wet filler — it’ll crack and peel
- Leaving the filler below the surface — you’ll see a dent even under paint
- Skipping primer — you’ll see the patch through the paint
- Using exterior filler inside — it’s too hard and difficult to sand
- Using too much filler on one go for a deep hole — do it in layers
What filler should I use?
For most household holes, a standard ready-mix interior filler (Polycell Fine Surface, Ronseal Smooth Finish, or own-brand equivalent) will do the job. It’s easy to use, sands well and is sold in tubs you can keep resealing.
- Small holes (nail, screw): standard ready-mix filler
- Hairline cracks: fine surface filler or flexible decorator’s caulk
- Large holes: base coat with bonding or lightweight compound, then finish with ready-mix
- Damp areas: use a waterproof filler
We stock filler, filling knives, sandpaper, primer and paint at 248–250 Lavender Hill — everything you need to get it done in one trip.
Everything you need — open 7 days
Filler, sandpaper, primer, paint and filling knives all in stock at Clapham Junction Discount Store, 248–250 Lavender Hill, SW11 1LJ. No delivery wait — come in and take it home.