How to patch a hole in drywall or plasterboard: dents, small and large holes

Safety first

• Cables and pipes often run vertically above and below sockets and switches, and horizontally across from them. Avoid cutting in those lines.
• A cable and pipe detector is inexpensive and worth using before you cut.
• If you need to cut, make a shallow scoring cut first and look inside before going deeper.
• Wear safety glasses when cutting and a dust mask when sanding; filler and plaster dust is fine and gets everywhere.
• In older homes, be careful with walls and paint that may contain hazardous materials. If you are unsure what an old wall is made of or painted with, get it checked before sanding or cutting.

What you need

• Ready-mixed filler or lightweight joint compound
• A flexible filling knife (a narrow one and a wide one)
• Fine sandpaper or a sanding block
• Self-adhesive mesh patches for medium holes
• An offcut of plasterboard, a pencil, a utility knife and a small saw for large holes
• Primer and matching paint

Dents, dings and screw holes

1. Scrape away any loose paper or crumbs around the damage.
2. Press filler into the dent with the knife and draw it flat across the surface.
3. Let it dry fully. Deeper fillings shrink, so a second thin coat is normal.
4. Sand smooth with fine paper, wipe off the dust, then prime and paint.

Medium holes (up to about the size of a fist)

1. Trim ragged edges so the area around the hole is flat and firm.
2. Stick the mesh patch centrally over the hole, pressing it down well.
3. Spread a thin coat of filler over the patch, feathering it out a few centimetres beyond the edges.
4. Let it dry, then add a second and possibly third thin coat, each a little wider than the last. Several thin coats are better than one thick one, which cracks and sags.
5. Sand between coats if needed, then sand the final coat smooth.

Large holes: fit a new piece

1. Draw a neat square or rectangle around the damage and cut it out.
2. Fix timber battens or strips inside the hole, screwed through the existing board at top and bottom, so the new piece has something to fix to. If the hole lands on a stud, you can fix straight to that.
3. Cut a plasterboard patch to fit the opening and screw it to the battens, sinking the screw heads just below the surface without tearing the paper.
4. Tape the joints with joint tape or mesh tape, then fill and feather as above, building up thin coats until the patch disappears.

Getting an invisible finish

• Feather the edges. The secret of a repair you cannot see is spreading filler wide and thin so there is no ridge.
• Check with a light. Hold a torch flat against the wall; it shows every bump and hollow.
• Prime before painting. Bare filler soaks up paint differently, leaving a dull patch (called flashing) even with the right colour.
• Paint a whole section. Touching up just the patch often shows. Painting the wall from corner to corner, or at least to a natural break, blends best.

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