Originally Posted By: jedwards
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; you can see the condensation droplets on the top of the hatch frame to the right (photo taken today, outside temp <60, hatch hadn’t been opened for some time). The room above has some moisture stains and mold on the paneling from an ongoing roof leak that needs attention, over the same end of the room as this photo.
The photo shows the underside of the poured concrete floor of the original porch. It's caked with dirt. It's not WDI. At this end of the crawl, it's as much as an inch thick. Back toward the other end of the crawl it thins out but there's at least a dusting all the way, 10' or so to the opposite end with decreasing overhead clearance.
This crawl has obviously been a moisture issue for a long time. You can see some fresh mold spots on the brick in the photo. The upper surface of the floor in the room itself has a dusting of mold throughout from water that's wicked up through the concrete over the years. The only thing I can come up with is that it gets so wet in this crawl during the summer (it gets to 90F plus and damned humid in these parts) that over the course of 60 years the dirt has been deposited by rising water vapor from the moist soil underneath. Only about 24" vertical clearance at most. The coating is thicker near this end of the crawl under the leak problem, which would make sense.
FWIW, the main crawl under the rest of the house is well-vented and dry as a bone.
Ever seen this? Better explanation? Anybody?