Just finished tearing out old bathroom walls for remodel. I noticed a small amount of mold on the backside of the plywood of an exterior wall. Areas with no insulation did not have any mold, backside of drywall had no mold. There was a small amount of water leaking from from the bottom of the shower, but that is no where near the wall with the mold. It appears like it was condensation, no obvious signs of water running down the inside of the walls. No signs of leaking in the attic. This is on an upstairs bath of home built in 2000, stucco walls. Does anyone know if this is normal for exterior walls? Any simple fixes?
The sheathing with no insulation would be warmer and condensation less likely to form on it. The vapour check should normally stop any moisture penetrating through to the plywood, unless there was a defect in it. This link might help. http://www.lifecote.biz/14.html