By Barry Stone
Dear Barry,
The ceiling in our stall shower continues to erode. We've installed a vent fan to expel moisture; we've replastered the ceiling and refinished it with exterior oil based enamel. Yet every few months, the plaster begins to decompose, and always in the same corner of the ceiling. Have you any idea what is happening? -- Mary
Dear Mary,
It sounds as though you've taken all the logical steps to curtail further moisture damage above your shower. Considering the thoroughness of these corrective and preventive measures, it seems unlikely that interior moisture is the cause of your problem. In fact, the most telling symptom is the localized occurrence at the shower corner. This may indicate that roof leakage is occurring where the drain vent pipe penetrates the roof flashing.
Before attempting further repairs, have the roofing and flashing reviewed by a licensed roofing contractor or a qualified and experienced home inspector.
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