High relative humidity in below-grade slab and flooring
I live in the Denver area and am remodeling the below-grade area of the house. It’s slab on dirt, without capillary break (1958), about 4′ below grade, and with soil that is 60% Sand, 20% Silt, 20% Clay.
I have a lignomat concrete moisture meter, that uses the bored-hole approach, and have tested a number of locations.
I’m consistently getting readings 80-93% RH, and I had the RH probe calibrated to confirm it is not off.
Significant drainage work has occurred around the house, with no evidence of bulk moisture, though a seasonal irrigation ditch/stream runs in the front yard, about 100′ away, and this soil drains very well. It is also an atypical year with high precipitation.
If I was to seal or vapor barrier the exposed slab, would this potentially lead to rot or dry-rot of the framing that rests on the slab and stem wall? New framing is treated with a thick layer of glue underneath, but who knows about the 1958 framing.