Why does moisture stay in the walls after the floor is dry?
Moisture moves slowly through porous materials and it can stay in a wall cavity long after the floor surface feels dry. It moves toward the drier air in the room, and the drying equipment helps it along. The wall is read directly rather than judged by its surface.
Water travels from wet materials toward dry ones, and it moves at different speeds through different materials. A floor covering can feel dry while the subfloor beneath it still holds moisture. A wall cavity can keep its wetness behind a drywall skin that looks sound. The reading is the only reliable test, because the surface is a poor guide to what the material holds underneath.
The air in a room has a role too. Drying works by lowering the moisture in the air so that water leaves the materials and moves into it. A room that is closed up and warm can hold a great deal of moisture in its air. A dehumidifier pulls that vapor out and holds it, which keeps the drying gradient moving in the right direction.
What do air movers and dehumidifiers actually do?
Air movers push air across wet surfaces to speed evaporation at the surface and move moisture toward openings. Dehumidifiers remove water vapor from the air, keeping the air able to take on more moisture. Used together, they lower the moisture held in the materials.
An air mover is a fan built to move a high volume of air across a wet surface. It does not remove moisture from the room by itself. Its job is to carry moisture-laden air away from the surface and to keep a fresh layer of air moving across the material, so that evaporation continues. Placing it at the wrong angle or height wastes its effect.
A dehumidifier takes water out of the air by cooling it so vapor condenses, or by passing it over a material that absorbs moisture. The water is collected or drained away. Without a dehumidifier, the air in a sealed room can become saturated and stop taking moisture from the materials, so the drying slows even with air movers running.
How does a crew decide where the equipment goes?
The crew places equipment where the readings are highest and where the air can reach the wet material. Layout is drawn for each room, checked against the readings, and moved as those readings change. The aim is to move moisture out of the building, not just move air around it.
Equipment placement starts with the readings. The technician looks for the wettest points, usually along the lower wall and at the floor edge, and aims air movers so that the flow crosses those points and continues outward. Equipment placed in the middle of a room with dry surfaces does little for the wet ones.
The layout is redrawn as the work progresses. A room that has reached dry levels gets its equipment moved to the next wet area. Doors are kept closed to hold the air in the drying zone, and vents or openings are used where they help. The homeowner is asked to keep the equipment and its cords out of the walkways.
Why does the crew open walls during drying?
Air cannot reach moisture trapped in a closed wall cavity. The crew opens a small section at the base of the wall so air can move into it, and the insulation and framing are checked. The openings are kept as small as the readings permit.
A closed cavity behaves like a sealed box. The water in its insulation and its framing will not reach the room air until something opens a path. The crew cuts an opening at the lowest point with the readings in hand, so that the drying air can enter at the bottom and carry moisture up and out of the cavity.
Each opening is recorded with its location and the reading that prompted it. Insulation that has taken on water is removed, because it holds moisture and keeps the wall wet even when the framing is dry. The technician explains every opening to the homeowner and notes what it found.
What affects the length and scope of structural drying?
The length depends on the materials, the depth of the wetting, the openings needed and how well the building can be kept closed. No figure is set here. The schedule follows the readings, and the price is explained and approved before work starts.
Materials decide much of the timeline. Dense solid wood dries more slowly than a thin board, and thick plaster holds more water than drywall. A building with many cavities, a basement with heavy finishes or a crawl space with insulation all add time, because each place holds moisture that has to be reached.
The building itself can help or hinder the work. A house that stays closed and warm dries better than one with open doors and cold air, and the crew asks the homeowner to keep the building closed except where the equipment needs access. The technician sets out the schedule on the first visit and updates it as the readings come in.