How does structural drying actually remove water from a wall or a floor?
Water moves out of a material when the air around it is drier than the material. Air movers increase the rate at which moisture leaves the surface, and dehumidifiers lower the humidity in the room so that the moisture can keep moving into the air. The process is slow inside dense materials.
A wet material releases moisture into the air around it until the two reach a balance. If the air is already humid, the balance is reached before the material is dry. Dehumidifiers lower the humidity so the balance point keeps moving, and air movers keep fresh air in contact with the surface so the process continues.
Wood and drywall hold water differently. Wood holds moisture in its cell structure and releases it slowly, while drywall releases water faster from its surface but holds it in the core. The drying plan accounts for this difference, and that is why the readings are taken at more than one depth.
What is a dry standard, and who decides it?
A dry standard is the target moisture reading for a material, set by comparing the wet material with an unaffected material of the same kind in the same building. The technician sets the target, records it and checks the material against it at each visit.
Each material has its own target. A reading that is normal for one kind of wood can be too high for another, and drywall has a different scale from framing. Setting the target from an unaffected area of the same material keeps the comparison honest and means the target reflects the building.
The homeowner can ask to see the target and the readings for each material. A crew that uses a clear standard can show you the numbers, and the numbers are the only proof that the building is dry. Ask what the target is and when the next reading will be taken.
Why does the humidity in the house matter so much?
The humidity of the air decides how quickly materials can release water. In a humid climate and in a closed-up house, the air holds the moisture the materials release, so drying slows. Dehumidifiers and ventilation are used to lower the humidity and keep drying on course.
Windows that stay closed trap moisture in the house. Storm rain, humid days and damp air from outside all add water to the room air, and the materials then take longer to release what they hold. The crew measures the room air as well as the materials, so the drying can be adjusted.
Running a household air conditioner or dehumidifier can help, but it is not a substitute for the crew's equipment. Household units are sized for normal conditions, not for a room where a wet wall is releasing water. Ask the technician whether your own equipment should run, and where.
How long does structural drying usually take?
The time depends on how much water went where, what materials are involved and how humid the air is. Drying is measured in readings and not in days, so the crew does not promise a fixed length of time. The log shows when the work is complete.
A small area of wet drywall in a dry room may dry in a few days. A soaked subfloor, a wet crawl space or a cellar with water in its lower walls can take much longer, sometimes weeks, because the moisture has to travel through thicker material.
Ask the technician for an estimate of how the drying should progress, and expect the readings to fall steadily at first and then more slowly as they approach the target. If a reading stops falling, the crew should explain why and change the plan.
Can I run a fan and a dehumidifier myself while the crew is working?
A household fan can help move air once the water is out, but it should be placed and run with the crew's advice. Running equipment without a plan can move moisture into clean rooms, and an unsuitable dehumidifier can waste time without removing much water.
Ask the technician where to place a household fan, and keep it out of the wet area if it would blow moist air into rooms that are already dry. Do not run extension cords across wet floors, and do not place a unit where water could reach its electrical parts.
Keep the doors and the windows set as the technician asks. Closing a room to hold the drying equipment in can help, but opening the windows at the wrong time can add humid outside air. The crew sets the house up for drying and explains each change.