The quick diagnosis
Most paint failures fall into a handful of patterns. Matching what you can see to the likely cause is the first step.
| What you see | Likely cause |
|---|---|
| Paint peeling in sheets from new plaster | No mist coat, or paint applied before plaster was dry |
| Bubbles or blisters on walls | Damp, moisture trapped behind paint, or heat on fresh paint |
| Flaking on ceilings in bathrooms and kitchens | Condensation, or emulsion over old distemper |
| Peeling gloss on woodwork | Painting over dirt, grease, or gloss without sanding |
| Fine 'crazing' cracks | Thick coats, or a hard paint over a softer one |
| Deep 'alligator' cracking | Many layers of old oil-based paint, or incompatible coats |
| Exterior paint flaking off masonry | Moisture in the wall, or chalky surface not stabilised |
| Yellow or brown patches bleeding through | Stains, nicotine, knots or tannins not sealed |
Common paint defects and their usual causes
Damp: the most common culprit
Moisture is behind more paint failures than anything else. Water from a leak, rising or penetrating damp, or condensation gets behind the paint film and pushes it off the surface. Blisters that contain water, salty white deposits and paint that peels along the bottom of walls all point to damp.
No paint fixes damp. The source has to be found and cured, the wall allowed to dry out – which can take weeks or months – and then the surface prepared again. See damp and mould before painting for what to check.
New plaster and old distemper
Fresh plaster is very porous. If ordinary emulsion goes straight on, it dries on the surface without bonding, and later peels off like a skin. The fix is a mist coat – a watered-down first coat of contract matt – once the plaster has fully dried. See painting new plaster.
In older houses, ceilings were often painted with distemper, a chalky, water-soluble paint. Modern emulsion doesn't bond to distemper and peels in flakes, especially in damp rooms. The distemper needs washing off, or sealing with a specialist stabilising primer, before repainting.
Woodwork problems
Gloss and satinwood peel from woodwork that wasn't cleaned or sanded, especially where water-based paint has gone over old oil-based gloss without a suitable primer. Knots weep resin through paint unless sealed with knotting solution. Outside, moisture in the timber – from rot, poor joints or failed putty – lifts paint from window sills and the bottom of doors.
See painting over gloss without sanding and painting woodwork.
Rather leave it to a professional?
Cracking and crazing
Fine cracks often appear where paint was put on too thickly, where filler wasn't fully dry, or where a hard paint has gone over a softer, more flexible one. Old houses with decades of oil-based paint layers can develop deep 'alligator' cracking as those layers lose flexibility. Sometimes the only real fix is stripping back to bare wood or plaster.
Cracks that run in straight lines along joints in plasterboard, or across ceilings, are usually movement in the building or the boards rather than paint failure. Those need filling with a flexible filler or scrim tape before repainting – see caulk vs filler.
How a decorator puts it right
Old paint in houses built before the 1970s may contain lead. Don't dry sand or burn it off without precautions – see lead paint and Artex.
- Find and deal with the cause – damp, condensation, poor ventilation
- Scrape back all loose and flaking paint to a firm edge
- Fill, sand and feather the edges so they don't show through
- Use the right primer or sealer for the surface
- Apply topcoats in the right conditions with proper drying time
When to call a professional
Small areas of peeling paint can be a DIY fix. Widespread failures, peeling ceilings, problems that keep coming back, or anything involving damp or old paint are better handled by a decorator who can diagnose the cause and prepare surfaces properly. Get quotes from local painters and decorators, and ask each one what they think is causing the problem.
