2026-09-17 · Dave Kessler · 4 min read
Mold in North York Homes
Older block, a lot of storage, and summers that sweat the walls.
Block and boxes
The radon pattern for these houses is on the North York page. The mold pattern is simpler: cold block, July air, and paper. Block and stone is the cleaning piece.
Winter is not a free pass
Houses stay closed, cooking and showers still happen, and a cold corner will grow mildew even when the rest of the basement looks fine. A gauge in January is worth as much as a gauge in July.
Finishing
If you want a room, give the wall a way to dry or a real drainage path. Do not screw drywall to furring on a wall that fails the foil test.
Questions people also ask
+Are North York basements wetter than East York?
+Should I run a dehumidifier in winter?
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.