Flaking, peeling, blistering and cracking paint can occur with age, when moisture collects under a painted surface, or when paint is applied to a damp surface. Moisture enters the surface of wood or drywall from the unpainted side, gets absorbed then dries. This causes repeated swelling and shrinking of the surface, which makes the paint pull away, leaving it blistered, cracked or peeling. Locate any sources of moisture by checking the area around peeling paint. Excess heat and moisture can cause condensation that eventually leads to trouble in areas such as the bathroom or kitchen.
Over time, a layer of paint may simply become brittle and split. This creates hairline cracks on the surface layer which then become larger and cause the paint to flake or peel.
To fix this, remove all peeling or flaking paint with a paint scraper or wire brush. Next, sand the surface. You can rent or buy a disc sander with 60, 80 and 120-grit sanding discs. For very limited areas, use a random-orbit sander, hand sander or disc sander drill attachment. Begin sanding with a coarse abrasive and finish with a fine one. Pay particular attention to smoothing the edges between painted and scraped areas. This is called feathering. Painting will accentuate, not hide, any ridges and edges you leave.
When repainting, avoid using low-quality paint that has inadequate adhesion and flexibility. When painting, don’t spread it too thin during application. Use a primer before painting for better adhesion.