What the meters show
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. Painted drywall dries at the face while the gypsum core and the stud behind it stay wet. Seal it up or push furniture against it, and mold can grow out of sight for weeks.
The drying target comes from what techs call the dry standard: readings taken on unaffected drywall, framing or flooring elsewhere in the house. When the wet wall reads within range of that dry standard, it is dry; until then, the equipment keeps running.
Wood floors make the point just as clearly. With a slow leak under a dishwasher, the underside of the boards swells and the edges lift, which is called cupping. Sanding it flat too soon leaves the floor crowned once it finishes drying. Drying mats and patient monitoring often let the boards settle back down.
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 is how full the air is relative to what it can hold at that 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