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Peeling paint---"suspects there may also be a layer of wallpaper"

I can think of at least 3 other reasons the paint could peel and crack. 1. Is it possible moisture could be seeping through the old wall? 2.If water based paint was used over old lime based plaster, the lime eventually corrodes through the paint. (must use a shellac or oil-based primer 1st.) 3.Many old walls have been sealed with silicone sealers or have a waxed coating. Either would prevent paint adhesion and would need to be removed prior to priming.