Notes from the drying techs
Dry to the Touch Is Not Dry
Here is a call the dispatch desk gets every week: a leak was fixed, the wall looks fine, but a tech puts a meter on it and it reads high. 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 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
- Vapor pressure moves moisture from wetter materials toward drier air
- Dew point tells the tech where condensation could form on cold slabs and outside walls