Peeling paint, cracking and blistering all mean the paint has lost its grip on the surface, and the cause is usually moisture, poor adhesion, incompatible coatings, heat or chalky old paint. The fix is always the same in principle: find and remove the cause, take the failed paint back to a firm edge, prepare and prime, then recoat. Painting over the problem without fixing the cause only brings it back.
How to tell peeling, cracking, flaking and blistering apart
These problems often appear together, but they have different starting points. Dulux describes cracking and flaking as the splitting of a dry paint film, which starts as hairline cracks and develops into flaking chips. Blistering, Dulux says, results from the loss of adhesion between the paint and the surface underneath.
| Defect | What it looks like | Usual causes | The fix |
|---|---|---|---|
| Peeling | Sheets or strips of paint lifting away | Moisture behind the paint, dirty or glossy surface, no primer | Fix moisture, scrape back, sand, prime, recoat |
| Cracking | Fine lines that may go through to the surface | Brittle old paint, movement in timber or render, thick coats | Remove loose paint, feather edges, fill, prime, recoat |
| Flaking | Small chips breaking away along cracks | Cracking that has let water in | Scrape back to a firm edge, prime, recoat |
| Blistering | Bubbles under the paint film | Moisture, heat, painting in direct sun, trapped solvents | Cut out blisters, fix the cause, prime, recoat |
| Chalking | Powder that rubs off on your hand | Paint film wearing away from weathering | Clean back to a firm surface, seal, recoat |
Why is my paint peeling?
Moisture getting behind the paint
Moisture is the most common cause of peeling paint outside. Dulux identifies moisture trapped beneath the surface of the paint film as a leading cause of blistering and flaking. Water gets in through leaking gutters, failed sealant around windows, unsealed end grain on weatherboards, rising damp in render, or garden beds piled against walls. Inside, it’s usually steam in bathrooms and laundries.
The paint itself isn’t the problem here. Fix the water source first, or new paint will fail the same way. Our guides to painting weatherboard houses and painting rendered walls cover the usual water paths on each surface, and our article on painting kitchens and bathrooms deals with moisture indoors.
Poor adhesion
Paint needs a clean, sound, slightly keyed surface to grip. Peeling often follows painting over:
- dirt, grease, cobwebs or mould
- powdery or chalky old paint
- glossy enamel that hasn’t been sanded
- bare timber or masonry with no primer
Incompatible paints
Some coatings don’t bond well to each other. Dulux’s trade advice notes that water-based coatings may blister if applied over surfaces previously painted with solvent-based paints. This is common on older homes where trims were painted with oil-based enamel and later recoated with acrylic without sanding or priming.
If you’re not sure what’s on a surface, a painter can test it and recommend a primer that bonds to both.
What causes paint to crack?
Paint cracks when the film can no longer stretch with the surface underneath.
- Old, brittle paint. Older oil-based paints harden over time and crack as timber expands and contracts.
- Movement in the surface. Dulux notes that movement at joints, such as window frames, can split the paint and let moisture in, which then causes flaking.
- Coats applied too thickly. Dulux says mud cracking, a pattern like dried mud, is usually caused by a thick, heavy, unthinned coat, especially on textured surfaces.
- Poor product or no primer. Haymes lists low-quality paint, imprecise application and a missing primer among the causes of cracking.
Haymes’ fix is to remove loose paint with a scraper or wire brush, feather the edges of the crack before priming, and strip the whole paint layer if the cracking goes right through.
Why does paint blister?
Moisture blisters
If you cut open a blister and find bare timber or masonry underneath, moisture is the most likely cause. Water or water vapour is pushing out from behind the paint. Fix the source, then repaint.
Heat and sun blisters
If only the newest coat has lifted, heat is the more likely culprit. Painting in direct sun or on a hot surface makes the top of the film dry too fast, trapping solvent or water underneath. Haymes advises not painting directly in the sunlight and warns that painting above 32°C or below 10°C can cause bubbling. Dulux also notes that dark colours absorb more heat than light colours, and that resin in timber knots can cause blistering, especially under dark colours in full sun.
That’s one reason timing matters. Our article on the best time to paint your house exterior in Melbourne explains how to work around the weather.
Chalking: the problem underneath the problem
Chalking is a fine powder on the surface of old paint. Dulux describes it as a wearing away of the paint film by weathering. Chalking by itself isn’t a failure. It’s what exterior paint does as it ages. But if you paint over it, the new paint sticks to loose powder instead of the wall, and it will peel.
To fix it, Dulux recommends brushing off the powdery material with a stiff bristle brush and applying a stabilising primer. For Australian products, Dulux advises you sand back to a strongly bound surface and dust off before priming.
How to fix failed paint properly
Whatever the defect, the repair follows the same steps:
- Find the cause. Look for leaks, failed sealant, damp, or a surface that was never properly prepared.
- Test for lead in older homes. Dulux states that most Australian homes built before 1970 were painted with lead-based paint. Read our guide to lead paint in older homes before you scrape or sand.
- Remove loose paint back to a firm edge. Dulux recommends stripping back to the bare surface if large areas are affected.
- Clean and sand. Wash with sugar soap, sand glossy areas, and feather the edges so the repair doesn’t show.
- Fill and seal. Use flexible fillers and sealants in joints that move.
- Spot prime bare areas with a primer that suits the surface.
- Recoat in good conditions, within the temperature range on the tin.
Small areas of peeling on a fence or a ground-floor window frame are fine to tackle yourself if you follow those steps. Widespread failure across a whole elevation usually means a full strip-back and repaint. AMP Master Painters has fixed failing paint on Melbourne homes since 1998, and our exterior painting and interior painting work comes with a written 7-year guarantee. If you’re not sure whether to patch or repaint, our guide to how often to repaint your house can help.
The bottom line
Peeling paint, cracks and blisters are warnings, not just cosmetic faults. Each one points to a cause: moisture, poor adhesion, incompatible paints, heat or chalky old coatings. Fix that cause, prepare the surface properly and prime before repainting, and the new finish will last. Skip those steps and the problem comes straight back.
