I am a Realtor and have listed a brick home built in 1936 with plaster/lath walls. The south facing wall had ivy on it until last September. The inside p/l wall had some scaling that we scraped off, applied drywall mud, sanded, and painted. Within a week there was new scaling. We repeated the process, tried sealing with spray paint, dried with a space heater, etc, everytime the scaling returns. Any suggestions?