Notes from the drying techs
Why Dry to the Touch Does Not Mean 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. Drywall paint dries on the surface first and seals moisture inside the gypsum core and the stud behind it. Seal it up or push furniture against it, and mold can grow out of sight for weeks.
Drying techs set goals by reading the same material in a part of the house the water never touched. 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 is how full the air is relative to what it can hold at that temperature
- GPP is the actual weight of water vapor in the air, which is the number techs track day to day
- 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