We've lived in this house for almost 3 years now, and every now and then, a spot of mold (5-7" long, 2-5" wide) will appear on outside walls where the ceiling meets the wall. i've been all over the attic (not fun) looking for damp roofing and rafters, and I even opened up the soffits outside to look at the top of the drywall, and everything looks fine. I cannot figure out where the mold is coming from. any ideas?
my brother in law suggested my attic does not have enough ventilation. right now it has one fan in the middle of the house, and vents every 8' or so in the soffits in the overhangs.
thanks.
dave