Paint failures are frustrating, but they're rarely mysterious. Almost every problem has a specific cause, and once you know it, the fix is straightforward. The rule that covers nearly all of them: fix the cause first, then repaint. Painting over a failure without fixing the cause just schedules the next failure.
Peeling and flaking
What it looks like: paint lifting off in flakes or sheets, sometimes down to bare wood or an older coat.
Common causes: moisture getting behind the paint, painting over dirt, chalk or gloss, latex over unprimed oil paint, or paint applied in conditions that were too cold or damp.
Fix: find and stop the moisture source (leaks, missing gutters, poor bathroom ventilation). Scrape all loose paint, feather sand the edges, clean, prime bare areas and any glossy surfaces, and repaint. On homes built before 1978, use lead-safe practices; see lead-safe renovation.
Blistering
What it looks like: bubbles in the paint film.
Causes: heat blisters form when paint is applied in direct hot sun and the surface skins over while solvent or water is trapped. Moisture blisters form when water vapor pushes out from behind the paint, common on exterior walls of bathrooms and kitchens.
Fix: cut open a blister. If it has bare wood underneath, suspect moisture; if it has paint underneath, suspect heat. Scrape, sand, fix moisture sources, prime and repaint in the shade.
Cracking and alligatoring
What it looks like: fine cracks, or a pattern like alligator skin.
Causes: paint that has become brittle with age (especially old oil paint), paint applied too thickly, or a hard coat over a softer one that moves differently.
Fix: light cracking can be scraped and sanded smooth. Alligatoring usually means removing the paint down to a sound surface, then priming and repainting. Old alligatored paint is often lead paint, so test first.
Flashing and uneven sheen
What it looks like: patches that look shinier or duller than the rest of the wall, often around patches.
Causes: unprimed patches, cut-in edges that dried before rolling, or uneven film thickness.
Fix: spot-prime patches, then repaint the whole wall corner to corner while keeping a wet edge.
Lap marks and roller stripes
What it looks like: visible stripes where wet paint overlapped paint that had begun to dry.
Fix: sand lightly if needed and repaint the wall in one continuous session, working in manageable sections and keeping a wet edge. Avoid painting in direct sun or with a fan blowing on the wall.
Picture framing
What it looks like: a band around the edges of a wall that looks different from the middle.
Fix: cut in and roll one wall at a time so they blend while wet, and roll as close to the edges as possible.
Mildew
What it looks like: gray, black or green spots, common in bathrooms, on north-facing exterior walls and in shady, damp areas.
Test: dab a spot with diluted household bleach. If it lightens, it's likely mildew; if not, it's probably dirt.
Fix: clean with a mildew cleaner, rinse, let dry and repaint with a mildew-resistant paint. Improve ventilation; in bathrooms, run the fan during and after showers.
Tannin bleed
What it looks like: brown or yellow stains coming through paint on cedar, redwood, oak or knots.
Fix: prime with a stain-blocking primer suitable for tannins (oil-based or shellac-based primers are the traditional choice), then repaint.
Surfactant leaching
What it looks like: sticky, shiny tan, white or brown drips or streaks, usually on fresh latex paint in bathrooms or on exteriors after dew or rain.
Cause: the paint's water-soluble ingredients come to the surface when the paint is exposed to moisture before it fully cures.
Fix: it usually washes off with warm soapy water and may take a few washings. It typically doesn't affect long-term performance once the paint cures.
Chalking
What it looks like: a powdery residue on exterior paint that rubs off on your hand.
Fix: wash the chalk off thoroughly. If it's heavy, use a primer that's suitable over chalky surfaces before repainting with a quality acrylic.
Poor hiding and color that looks blotchy
Causes: too few coats, paint spread too thin, a big color change without a tinted primer, or a low-quality paint.
Fix: apply the coverage rate on the label and plan two coats. Use a primer tinted toward the new color for big changes.
Doors and windows that stick
Cause: paint that hasn't cured, or a soft paint like wall paint used on trim. This is called blocking.
Fix: use a trim enamel designed to resist blocking, apply thin coats and give it time to cure before closing doors tightly.