DIY Quick-Fire: How do I fill holes and and cracks in walls?

Quick summary (TL;DR): Yes - you can fill holes and cracks without damaging the wall. Most repairs are cosmetic, and if you clean the area, use the right filler for the size, and let it dry properly, it’s a low-risk DIY job.

How do I fill holes and cracks in walls? Clean away loose bits and dust, press the right filler into the hole or crack (thin layers for deeper damage), smooth it flush, let it dry fully, then lightly sand and touch up with paint if needed.

Intro

Most people notice wall damage when a picture hook comes out, a wall plug leaves a crater, or a small crack appears after decorating. If you’re worried about making it worse, you’re not alone - but the good news is that most holes and cracks are cosmetic and very forgiving to fix.

This guide shows how to fill holes and cracks in walls for beginners (UK) using gentle methods first, then moving to deeper or more stubborn repairs. If you work slowly and match the filler to the size of the damage, you can get a neat finish without stressing the plaster.

Step 1: Work out what you’re dealing with

The method depends on size. A tiny nail hole needs a different approach to a rawlplug hole or a wider crack.

• Tiny holes / hairline cracks: pin holes, small picture hooks, fine surface lines
• Medium holes / wider cracks: screw holes, wall plug holes, cracks you can feel with a fingernail
• Large holes / blown plaster: a chunk missing, crumbly edges, deep cavities

Step 2: Prep properly (this is what prevents damage)

Clean and stabilise the edges

Most “failed filler” jobs fail because the filler was applied onto dust or loose plaster. Take 60 seconds to prep and the job becomes easy.

1. Brush away dust and loose bits (a dry paintbrush works well).
2. If the edge is crumbly, scrape it back to something solid.
3. For cracks, lightly open the crack so filler can grip (don’t gouge the wall).

Why this works: filler bonds to solid material. Dust and loose edges stop it sticking, which leads to sinking or cracking later.

Method 1: Filling tiny holes and hairline cracks

Best for: nail holes, pin holes, fine surface cracks

1. Use a small amount of ready-mixed filler on a filling knife.
2. Press filler into the hole or crack (don’t just smear it over the surface).
3. Wipe the surface smooth and flush.
4. Let it dry fully, then lightly sand if needed.

Why this works: small damage doesn’t need strength, just a tidy fill. Using less filler reduces shrinkage as it dries.

Method 2: Filling medium holes and wider cracks

Best for: wall plug holes, screw holes, cracks that reappear after paint

1. Remove loose material and dust.
2. Apply multi-purpose filler in thin layers (especially if the hole is deep).
3. Press firmly into the void so it fills properly.
4. Smooth flush, let dry, then add a second layer if it sinks back.
5. Sand lightly and touch up with paint.

Why this works: layering stops the filler from sagging or shrinking too much. Deep holes filled in one thick blob often crack as they dry.

Method 3: Repairing larger holes or blown plaster

Best for: chunks missing, deep cavities, crumbly edges

1. Cut back to solid edges and brush out dust.
2. Use a deep-fill/repair filler and build it up gradually.
3. Let each layer dry properly before adding more.
4. Finish with a thin smoothing layer for a paint-ready surface.
5. Sand gently when fully dry.

Why this works: repair fillers are designed to hold shape at depth. Building up in stages prevents cracking and gives a stronger repair.

Common mistakes to avoid (beginner-friendly)

• Overfilling: it seems safer, but it creates more sanding and can damage paint edges.
• Rushing drying time: filler that feels “dry” on top can still be soft underneath.
• Sanding too hard: let the sandpaper do the work — heavy pressure can scuff the surrounding wall.
• Skipping prep: filler won’t stick well to dust, loose plaster, or flaky paint.

When cracks might need extra attention

Most cracks are harmless, but it’s worth keeping an eye on cracks that keep growing or returning quickly. If cracks are widening over time or appearing around doors and windows, it can indicate movement. You can still fill them neatly, but repeated cracking usually means the wall is moving slightly rather than the filler being “wrong”.

FAQs

Do I need to repaint the whole wall after filling?

Usually not. If you smooth the filler flush and sand lightly, a small touch-up often blends in well. Larger repairs may show as a slightly different texture, so a bigger paint patch can help.

What if I make the hole look worse?

It’s very hard to cause permanent damage with filler. If it looks messy, let it dry, sand it back gently, and apply a thinner layer. Filler is forgiving and you can redo it.

Further reading

• How to remove a wall plug without damaging the wall
• How to stop wall plugs spinning
• How to drill into plaster walls safely
• How do I check for pipes, cables and studs before drilling?