Repair a cracked, damaged room before decorating

A step-by-step plan for repairing cracks, holes, blown plaster and coving before painting, with trade advice built in.

Guides in this project

01Fill cracks and holes before painting 02Patch a large hole in plasterboard 03Repair a patch of blown plaster 04Seal a crack between the wall and ceiling 05Repair damaged coving 06Sand walls and woodwork before painting 07Paint new plaster with a mist coat

RC-01Assess the damage and plan the jobWalk round the room and note every crack, hole, blown patch, and bit of damaged coving. Match each defect to the right HomeGraft guide so you buy all your materials in one trip instead of several. Check for cables and pipes with a detector before marking up anything for cutting or drilling, and still expect to find something even where the detector reads clear. Block out 3–5 days for this job, ideally spread over one or two weekends, so repairs have time to dry between stages.

1 each · Cable and pipe detector

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2 each · Dust sheets

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1 roll · Masking tape

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RC-02Fill hairline cracks and small holesUse the 'Fill cracks and holes before painting' guide for any crack narrower than about 5mm and any small nail or screw holes. Do this first, it's the quickest job and clears the small stuff before you move on to bigger repairs. Let filler cure fully, usually overnight, before you sand it back.

1 tub (1kg) · Fine surface filler

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1 each · Filling knife

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RC-03Patch large holes in plasterboardFollow the 'Patch a large hole in plasterboard' guide for any hole bigger than a fist, for example where a towel rail or shelf has come off. Before cutting into the board, check again for cables with a detector, even near switches, since wiring often runs close by. If a socket or switch faceplate needs to come off, switch the circuit off at the consumer unit and prove it's dead with a tester first; if any cable needs extending or moving, call a registered electrician rather than doing it yourself.

RULES

1 sheet · Plasterboard offcut

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1 pack (50) · Plasterboard screws

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1 tub (2kg) · Jointing filler

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1 roll · Scrim tape

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KNOW THE RULES

Extending or moving cables is electrical work for a registered electrician. Adding or moving a socket on an existing circuit isn't notifiable in England, but this can be notifiable in Wales, so check if you're unsure.

RC-04Repair blown plaster patchesFollow the 'Repair a patch of blown plaster' guide for any area that sounds hollow when you tap it. Work on this after the plasterboard patches so you're building out from solid, repaired areas. Allow new plaster at least 2–3 days to dry fully, longer in a cold or damp room, before moving to the next phase. If more than a couple of square metres are blown, it's worth getting a plasterer in rather than tackling it all yourself, since a large skim coat is hard to finish flat.

1 bag (5kg) · Bonding/finishing plaster

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1 litre · PVA bonding agent

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1 each · Plasterer's trowel

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RC-05Seal the crack between wall and ceilingUse the 'Seal a crack between the wall and ceiling' guide for any gap along this joint. This crack often reopens if the house is still settling, so if it comes back within a few months of filling, get a builder or structural engineer to check for ongoing movement rather than just filling it again.

1 tube · Flexible decorator's caulk

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1 each · Caulking gun

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RC-06Repair damaged covingFollow the 'Repair damaged coving' guide for any broken, cracked or missing sections. Do this after the wall-to-ceiling crack is sealed, so the coving sits on a stable, filled edge. Support any loose coving while the adhesive sets, usually overnight, before you touch it again.

1 tub · Coving adhesive

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1 length (2m) · Coving offcut

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1 each · Mitre box

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RC-07Sand every repair smoothOnce all filler, plaster and adhesive are completely dry, follow the 'Sand walls and woodwork before painting' guide across the whole room, not just the repaired patches, so the finish looks even under paint. Wear a dust mask and open windows, this is usually the messiest day of the whole job.

1 each · Sanding block or sponge

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1 pack · Fine-grit sandpaper

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1 pack (5) · Dust mask

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RC-08Mist coat the new plaster and fillerFollow the 'Paint new plaster with a mist coat' guide over any fresh plaster, patched plasterboard or filled areas before your normal paint goes on. Skipping this lets new plaster suck moisture from your top coat, which shows up later as patchy, flat areas. Let the mist coat dry fully, usually a few hours, before deciding if it needs a second coat.

1 litre · Matt emulsion (for diluting)

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1 set · Roller and tray

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1 each · Paintbrush

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RC-09Final check before decoratingOnce everything is dry, run a hand over every repaired area to feel for ridges, and check under good side-lighting for shadows that will show through top coats. Expect the whole project to cost roughly £80–£250 in materials, depending on room size and how much damage you found, plus extra if you bring in a plasterer or electrician partway through. Keep leftover filler and paint for any snagging once your final decorating is done.

1 each · Work lamp (for inspection)

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