When peeling happens on the paint job of an interior wall or ceiling, the first thing you must suspect is some sort of moisture leak inside of or behind that wall. If it occurs on an painted outside wall, there might be moisture seeping in via small cracks or other openings in the siding or exterior masonry, or the water could be coming in through gaping joints around window frames and other trim on the outside of your house. Remember that the leak may not be immediately opposite the place where interior peeling is detectable. Water can work its way into a wall, dripping down or traveling sidewise along a beam for some distance before really soaking into the plaster on the wall or ceiling of the house. In the same method, a roof leak at the top of the house can sometimes cause ceilings on stories below to blister and peel since water travels down through the wall until it hits a horizontal ceiling beam on the first floor. In most cases you’ll be able to tell whether or not water is the real cause of the trouble due to the characteristic staining on the plaster.
Even after a leak has been repaired, blistering and peeling of wall paint may sometimes go on after the wall surface has been repainted. A plausible cause is that the damage wasn’t properly repaired prior to the application of new paint. The old plaster could be crumbling or loose; unless it is decently patched, new paint applied to it will keep on peeling.
Paint peeling sometimes happens around the edges of metal casement windows due to condensation. As warm moist air coming from the inside condenses on the cold metal frame, the gathered moisture tends to seep into open joints between the plaster and the metal, filling the plaster and working its way out through the paint, causing the paint to blister and peel in the process. To avoid this, install storm windows when possible and put on caulking around both the inside and the outside of the frame.
In older houses and buildings, another more common cause of paint peeling is the accumulation of several layers of paint over brittle old coats that no longer bond properly. As every additional layer is applied the situation worsens, until ultimately whole sections start to crack and loosen. When this occurs, all the old coats of paint must be taken off with paint remover prior to the application of the new paint finish.
Another more common cause of paint peeling in kitchens, bathrooms and work areas is the failure to clean the surface thoroughly beforehand. Each paint can has instructions on the label which advise that the finish be applied only over a clean, dry surface, yet this warning is only too often ignored. Paint applied over a dirty or greasy surface won’t dry or adhere properly; it will often crack and peel back to expose the layer of dirty paint underneath.
This problem is especially acute around fireplaces and radiators, since wall parts near these units are frequently a lot dirtier than walls elsewhere. Wash the walls prior to painting; never apply paint when the wall or radiator is still hot. Brushing paint on a heated surface causes untimely drying, making it almost unimaginable to achieve a good bonding with the surface.
House Painting: Inside & Out by Mark Dixon and Bob Heidt
Painting and Finishing: Expert Advice from Start to Finish by Michael M. Dresdner