Sand back cracked or crazed paint, prime bare patches, then repaint in even coats for a smooth, lasting finish.
PA-01Work out why the paint crackedFine cracking or a spider-web crazing pattern usually means paint went on too thick, or a new coat sat on top of an old, incompatible finish. Damp can also cause it, so check if the wall feels cool or damp, or if it's in a bathroom or kitchen prone to condensation. Sort out the cause first, or the problem will just come back.
PA-02Clear and protect the roomMove furniture clear of the wall and lay dust sheets over the floor and any nearby surfaces. Open a window before you start sanding, so dust doesn't build up in the room. If the paintwork looks old, wear a dust mask - paint applied before the 1960s can contain lead, and sanding it releases dust you don't want to breathe in.
PA-03Scrape and sand back the damaged paintUse a paint scraper to lift off any loose or flaking paint, working back to a firm edge. Sand the whole area with 120-grit sandpaper until every trace of the cracked or crazed paint is gone, down to sound old paint or bare plaster. Run your fingers over it - if you feel ridges, keep sanding.
PA-04Feather the edgesSwitch to fine 240-grit sandpaper and lightly sand around the repair, blending the edge of the old paint into the surrounding wall. This stops a hard ridge or line showing through once you repaint. Wipe the area with a slightly damp cloth to pick up dust before moving on.
PA-05Fill any cracks underneathIf sanding has revealed cracks in the plaster or old filler underneath - not just in the paint layer - fill them with a fine surface filler using a filling knife. Leave it to dry fully, following the tin's drying time, then sand it smooth and flush with the wall around it.
PA-06Spot prime bare patchesApply a coat of watered-down emulsion (a mist coat) or a proper primer/sealer over any bare plaster or filled patches. This stops the topcoat soaking in unevenly and drying patchy. Let it dry fully before you carry on - check the tin for drying time.
0.5 litre · Primer/sealer or emulsion for mist coat
PA-07Apply the topcoatPaint the repaired area with your chosen topcoat, rolling large flat areas and cutting in edges and corners with a brush. Use two thin coats rather than one thick one - a thick coat is one of the main causes of cracking. Let each coat dry fully before adding the next.
PA-08Blend the patch into the wallFor a small repair, feather each coat outward at the edges so it fades into the surrounding paintwork rather than leaving a visible patch. If the colour or sheen still doesn't quite match, it's usually better to repaint the whole wall for an even finish.
PA-09Clean up and tidy awayWash rollers and brushes in warm water for water-based paint, or the correct solvent for oil-based paint. Fold dust sheets carefully so you don't scatter dust around the room. If any scraped paint could be old lead paint, bag it separately and check your council's guidance on disposing of it.
0.5 litre · White spirit (for oil-based paint clean-up)