Having bought an old house built in the 1950’s there are certainly plenty of holes and cracks in the walls. We counted over 200 plastic picture hooks around the house, and every one of them leaves a hole when it comes out. This post will show you how to fill holes or cracks in interior walls – both small and larger ones.

How to fill small holes or cracks

  1. You will need to buy a filling knife and some filler. Depending on the size of the hole you can get filler which works on really fine cracks or ones up to 2-3 cm. Any more than that and you should skip down to the next section – filling larger holes. There are a lot of brands but the best-known one is Polyfilla and the multi-purpose version is the one I tend to use. A filling knife differs from a normal paint scraper because it’s very flexible.
  2. First, pick at the hole or crack to see if you can loosen any paint or plaster manually – sandpaper might not always remove the big chunks
  3. Sand the hole or crack with some harsh/medium (60, 80 or 100 grit work well) sandpaper to get rid of any flaky paint or plaster still in the hole
  4. Apply a small amount of the filler to the filling knife and then into the hole or crack.
  5. Once the hole or crack is filled, scrape off any excess to leave the filler flush with the wall
  6. Leave it for 1-2 hours to dry properly. Once dry it might need to be sanded if it’s not completely even – use a slightly finer sandpaper this time (100 or 120 grit)
  7. If you want a really perfectly smooth finish, repeat steps 3-6 again. I didn’t do this when I was filling the holes and I can see some imperfections on the painted wall. Not huge, but if you’re a perfectionist you’ll appreciate the difference.
  8. Then all that’s left to do is paint it, and leave you as the only person who ever knew there was a hole or crack!

How to fill larger holes

  1. Here’s a bigger hole that Polyfilla won’t fill by itself – it’s about 10cm deep. An electrician took off the skirting board to get wires into a thermostat and left this gap – not great looking!
  2. I bought some single use expandable foam. It’s single use because the foam will fill up the applicator tube and it will be unusable once it dries. That’s enough for what I need it for anyway.
  3. Here’s a step which I didn’t do, but will help expansion if it’s a very large hole. Slightly wet the inside of the hole (assuming there are no electrics) – this will help the foam expand further.
  4. After attaching the applicator, shake the can for about 30 seconds, turn upside down and slowly squirt it into the hole. It will expand quickly so do this slowly.
  5. The foam will spill out of the hole, and as you let it dry (for about 30 mins) it will keep growing slowly. If you’re done with the foam, spray the remainder into a plastic bag – it’s not great to throw something so pressurised straight in the bin.
  6. Once it is dry to the touch, you need to cut it back so it is slightly below flush to the surface. Use a box cutter for this.

  7. Now you bring the Polyfilla in to finish the job and give a nice smooth surface.
  8. Sand this once it has dried, and if it’s not smooth, repeat steps 7 & 8.
  9. Then all you need to do is paint over the work and nobody will ever know!

-Seán

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