Notes from the drying techs
Why Dry to the Touch Does Not Mean Dry
A familiar story: the leak is repaired and the wall looks normal, yet the meter tells a different tale. Drywall paint dries on the surface first and seals moisture inside the gypsum core and the stud behind it. Close that up or hang a picture on it and you can end up with mold you will not see for weeks.
Drying techs set goals by reading the same material in a part of the house the water never touched. Only when the wet material matches that baseline is it considered dry, and not a day before.
Hardwood floors show the same problem in a different way. After a slow leak under a sink or dishwasher, the bottom of the boards takes on water and swells, so the edges rise and the floor cups. Sanding it flat too soon leaves the floor crowned once it finishes drying. Drying mats and steady monitoring can often bring the boards back flat.
The physics in plain words: warm, dry air pulls moisture out of wet materials, and dehumidifiers pull it out of the air. Air movers keep the surface boundary layer moving so evaporation does not stall.
- Relative humidity tells you how saturated the air is at its current temperature
- Grains per pound (GPP) measures how much water is actually in the air, regardless of temperature
- Moisture moves from high vapor pressure in wet materials toward lower pressure in drier air
- Dew point tells the tech where condensation could form on cold slabs and outside walls