Drying floors and walls in humid Mississippi air is slower than in a dry climate, because the air already holds moisture and cannot take much more from the materials. Dehumidifiers and air movers run together, and the job ends when the readings show each material is dry. The equipment is judged by the readings, not by a set number of days.
Key takeaways
- Drying works by moving moisture out of the material and then out of the air, so humid air slows the first step.
- Air movers speed evaporation, and dehumidifiers keep the air dry enough for evaporation to continue.
- Readings are taken at marked points, at the start, during the drying and at the end, to judge progress.
- A reading that stops falling means the setup must change; it does not mean the job is finished.
- A floor or wall is dry when it reads at the dry level for that material, not when it feels dry to the hand.
Why does humid air slow the drying?
Humid air already holds a lot of moisture, so it can take only a little more from a wet material. Evaporation slows, and the wet framing and subfloor release their water more slowly into the room.
Drying is a balance between the moisture in the material and the moisture in the air. When the air is nearly saturated, the balance moves slowly, and the material stays wet for longer than the surface suggests.
Mississippi summers and wet seasons bring humid air for much of the year. That is why a drying plan here allows for more days and checks readings more often than a plan written for a dry climate would.
What do air movers and dehumidifiers each do?
Air movers push air across wet surfaces to speed evaporation. Dehumidifiers remove moisture from the air, so the air can keep taking water from the materials. Each does a different job, and the two are run together.
An air mover on its own can raise the moisture in the room as it moves air, which slows the evaporation it was meant to speed up. A dehumidifier takes that moisture out of the air and keeps the drying going.
The positions matter. Air is directed across the wet surfaces and into the cavities, and the dehumidifier's exhaust is kept away from the rooms that stayed dry. A crew that sets the equipment without that plan is leaving the job to chance.
What do the readings measure, and where are they taken?
Moisture readings are taken on the framing, subfloor, drywall and floor covering at marked points, and the air in the room is checked too. The readings are compared with the starting point, and the end point is the dry reading for each material.
The points are marked on a simple plan so the same spots are read each time. A reading at the subfloor under a wet carpet is as important as a reading at the floor surface, because the subfloor is where the moisture stays longest.
The air readings show whether the room is still too humid to dry. If the air stays high, the dehumidifiers need adjusting or more of them are needed. The material readings show whether the drying is working.
How do you know a floor or wall is dry?
A floor or wall is dry when its readings reach the dry level for that material, measured at the same points as the start. Surface feel is not enough, because the subfloor and the cavity can stay wet under a dry-feeling surface.
The dry level differs for different materials, so the crew uses the level set for the framing, the subfloor or the drywall. A reading that matches the undamaged material next to the wet area is a clear sign of dry.
A reading that stops falling for several checks tells the crew that the drying is complete for that area or that something is still holding moisture. Either way, the crew looks at the cause before it closes the job.
Each material has its own dry reading, because the wood, the drywall and the concrete hold water in different ways. A subfloor that dries to a reading may still be above the level of the framing above it, and a wall cavity may need its own check after the surface has been dried. The plan should say which material each end point applies to, so nothing is closed up before every part has reached it.
What should a drying plan include for a floor and a wall?
A drying plan should name the points measured, the equipment and where it sits, the schedule of readings, the expected length of the run and the end point for each material. It should be given to the homeowner in writing.
The plan should say how the wall cavity will be reached, whether by a small opening or by the existing wall access, and how the floor will be dried from below if needed. It should also say what will be removed and why.
Ask the crew how the plan will change if a reading does not fall. A plan that allows for that is more likely to finish the job than one that is fixed from the first day.
How long should a drying run be expected to last?
The length depends on the material, the depth of the water and the humidity. In humid Mississippi air a floor and wall can take several days to reach dry readings. The crew sets an expected length after the first readings and updates it as the drying goes on.
A thin wet wall may dry quickly, while a thick subfloor or a wet crawl space can run for longer. The readings show the progress, and the expected end date moves with them.
Keep the readings in a file with their dates. They show you how the drying progressed and when the building reached dry, which is the record that matters for the rebuild.
What should the homeowner watch for during the drying?
Watch for equipment that has stopped, cords that are damp, a musty smell that is growing and any sign that a material is swelling or softening. Call the crew if you see any of these, and do not switch the equipment off without asking.
Check that the equipment is running and that its exhaust is clear. Keep the cords off wet floors and out of the path of foot traffic. A unit that is switched off without a reason can let moisture build back up in the room.
Keep a note of any change, with a dated photograph from the same spot. A change is easier to act on when the record shows when it began.
Why do some rooms in a house dry more slowly than others?
Rooms dry at different rates because of their size, their ventilation, their materials and where the water came from. A closed room with a thick subfloor dries more slowly than an open room with a thin finish. Each room has its own readings and its own plan.
A room with a closed door and no vent is slower to dry, because the moisture the dehumidifier removes is not replaced by fresh air. A room on the far side of the house may also lag behind, since the moist air from the wet room moves toward it.
The crew sets the equipment per room and checks each room on the schedule. A room that is not falling with the others is the first place to look for a hidden source or a poorly placed machine.
What should happen to the heating and cooling during drying?
Keep the heating and cooling system set so that it does not pull moist air from the wet area into the rest of the house. Close vents that carry air from the wet room if they can be reached, and ask the crew whether the system should run during the drying.
A running air handler can carry moisture and fine dust from the wet area through the ducts. The crew may ask for the system to be turned off or for the return vents in the wet area to be sealed, and it will explain the reason.
Do not change the thermostat settings or switch the system off without asking. The crew will tell you when the system can run as normal, and the readings will show whether the house is holding the drying.
What signs show the drying is not working?
Signs that drying is failing include readings that stop falling, a room that stays humid with the equipment running, a new smell or a material that keeps swelling. Each one is a reason for the crew to change the set-up and check for a source it may have missed.
A dehumidifier that is full, blocked or switched off cannot keep the air dry, and the readings will show it. Check that the unit is running and emptying, and that its exhaust is not blowing back into the room. Tell the crew what you find, since the fix is theirs to make.
A reading that climbs again after falling may point to a source that was not closed: a leak inside a wall, a crawl space that is still wet or a window that lets rain in. The crew should look at the cause, not only the equipment.
Frequently asked questions
Why do I need dehumidifiers if the fans are running?
Fans speed evaporation but add moisture to the air, and in humid weather the air stops taking water from the materials. Dehumidifiers remove that moisture and keep the drying going.
Can a floor dry under carpet?
Carpet and pad that are soaked usually need to come up, because the pad holds water against the subfloor. The subfloor is then dried from above and below, and the carpet is reinstalled once it reads dry.
Is the wall cavity going to be opened?
Only where the readings show water is held inside it and the drying cannot reach it from the room side. The crew opens the smallest area needed and records what it finds.
When can I put the furniture back?
Once the readings show the floor and walls are dry and the crew has confirmed the space is ready. Wet furniture should be dried separately and kept away from the walls until the room is dry.
How do I know the air in the room is dry enough?
The crew reads the air as well as the materials. The air readings show whether the dehumidifiers are keeping up. Ask for them with the material readings so you can see both.
This guide is general information for Lauderdale County homeowners, not a substitute for an on-site inspection. Prices are estimates. See our disclaimer.