Paint loose on walls

The paint on some of my walls is "loose", you can peel it off in small sheets. When you wipe your hand over the wall where the paint came off it leaves a white powder on the hand. Do I need to seal the wall ? What should I wash it with first and use to seal it? Any advice is very appreciated.
TIA jimmy
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first scrape all the loose stuff and address why its coming loose.... might be moisture troubles in the wall
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Sounds like an exterior wall, probably plaster. Latex paint cannot breathe so hydrostatic pressure pushes it off the wall and deteriorates the plaster to boot. Do NOT use latex on exterior plaster walls bonded directly to masonry.
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Most latexes do breath oils dont.
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Jimmy wrote:

Interior? Exterior? How old is the coat of paint? What kind of paint? It is normal outdoors for any kind of paint to take on chalking from weather. If that is what your are addressing, it needs to be pressure washed when ready to repaint. Peeling outdoors typically comes from some moisture getting into the wood (especially at joints/ends of wood siding), or applying paint before the surface dries completely. Lots of reasons for paint problems, and the more specific you can be, the better to get good advice. FWIF, all of the instructions on a can of good paint - prep, temperature, sun, cleaning, humidity, etc. - are there for very good reasons.
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Seems they painted without a primer coat? Seal it with an oil primer.
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