Loss of adhesion of a coating to the substrate (e.g. the surface that was painted) or an earlier coating. Where there is a primer and topcoat or multiple coats of paint, peeling may involve some or all of the coats.
Seepage of moisture through uncaulked joints or worn caulk.
Leaks in roof or walls, or excess moisture escaping through the walls from the interior.
Painting over a dirty, wet, or glossy surface.
Painting over a coating that already has marginal adhesion.
Remove old, loose, cracked caulk; prime as needed; and caulk with the appropriate product.
Find and repair any source of water.
Test the coating in a 6" to 12" radius around any peeled areas to be sure its adhesion is adequate.