2026-07-12 · Dave Kessler · 4 min read
Bathroom and Attic Mold
The cellar gets the reputation. The bath fan and the eaves do quiet damage.
Bathrooms
Look at the ceiling outside the shower, the back of the drywall under a window, and the exhaust duct in the attic if you can do it safely. A fan that flaps a tissue is not proof it exits the roof. Why the ceiling is the short version. Small spots on caulk are a cleaning job. A soft ceiling is a leak.
Attics
Ice dams and stuffed soffits are the winter story. Do not store the holiday bins against the roof deck. Do not add insulation over wet insulation and call it an upgrade. Window condensation in January is the indoor-humidity cousin, covered under does mold grow in winter.
What ties them to the basement work
We did not come to your house to re-roof it. We will tell you if the musty smell is clearly not the cellar, because we have watched people buy a second dehumidifier while the bath fan has been pointed at the insulation since 1998.
Questions people also ask
+How long should a bath fan run?
+Is ceiling mold dangerous?
These pages are homeowner education from Radon Mitigation of York, written by Dave Kessler. They are not a medical diagnosis, a species identification, or an insurance determination. Color does not tell you which mold you have. If someone in the house is sick, talk to a physician. EPA's homeowner guidance treats roughly 10 square feet as the line where many people stop DIY cleanup and call a remediation crew — sooner if sewage, HVAC, or anyone immunocompromised is involved. We are a radon and basement crew. When we are already under a York house we will tell you what we see and what we would do in our own place. We do not pretend a radon fan is a mold remedy.