Published by All Dry Services of the Bluegrass
Almost everyone with a wet floor starts the same way: open the windows, point a fan at it, borrow a dehumidifier. That approach is not wrong so much as incomplete, and understanding what it is missing explains most of what a restoration crew is actually doing.
What structural drying involves
Get the bulk water out. Extraction. Every gallon lifted mechanically is a gallon that does not have to be evaporated, and extraction is enormously faster than evaporation.
Move water from the material into the air. Air movers. Wet material holds a thin boundary layer of saturated air against its surface, which stops further evaporation. High-velocity air strips that layer away so the material can keep releasing.
Take the water back out of the air. Dehumidification. Without this, the air movers simply relocate the moisture to the coldest surface in the building, and you have moved the problem into the ceiling.
A fan alone does the second job and neither of the others. That is why a room can be blown at for a week and still fail a moisture reading.
The role of the dehumidifier
A domestic dehumidifier is built to hold a comfortable room at a comfortable humidity. It loses efficiency as the air gets drier and colder, which is precisely the condition you need at the end of a dry-out.
Low-grain refrigerant units are built for the other end of that curve. They keep pulling water at low humidity, which is what takes a structure to a dry standard rather than merely comfortable. That last stretch, from damp-but-not-obviously-wet down to dry, is where mold is prevented or not.
How we know when it is finished
Not by touch, and not by the calendar. We take a reading on unaffected material of the same type elsewhere in the building, and that becomes the target. The affected material is dry when it reaches it. Readings get logged daily and the equipment stays until the numbers agree, which is sometimes sooner than people expect and sometimes considerably later.
What has to come out
Not everything can be dried in place, and pretending otherwise costs more than the material is worth. Carpet pad is a sponge and is almost always replaced. Wet insulation loses its R value and holds water against framing indefinitely. Drywall that has wicked water high up the sheet gets cut back to a straight line above the damage, which is also why a good tear-out looks tidy rather than ragged.
Hardwood, framing and subfloor are usually savable, and often are, if the drying starts early enough. That is the argument for calling on day one rather than day four.
Humidity is a year-round issue here
Central Kentucky summers are humid, and a basement or crawlspace that sits above 60 percent relative humidity for weeks will grow mold without any leak at all. If you are drying out after a loss, it is worth asking whether the space was borderline before the loss too. Fixing that is cheaper than remediating it twice.