I have bought an old house - probably 1920's, 1930's and am trying to renovate the bathroom. The old ceiling has been painted with some sort of paint which in itself appears waterproof and is proving extremely difficult to get off. It is cracked in places. I tried sanding down and overpainting it with bathroom emulsion. this appeared ok for a while but then the old paint started to lift around the edges probably due to moisture and I am back to square one. Any ideas?