The three controls
Air movement
Still air next to a wet surface quickly becomes saturated and evaporation slows. Moving air replaces that layer with drier air, so evaporation continues.
Humidity
Evaporated water has to go somewhere. Dehumidifiers remove it from the air. If humidity is allowed to climb, drying stops and dry materials begin absorbing moisture.
Temperature
Warm materials release moisture faster. Too cold and drying crawls. Too hot and some materials, hardwood especially, can be damaged.
Free water and bound water
Liquid on a surface or in carpet is free water. It is removed by extraction. Water absorbed into wood fibers, drywall or concrete is bound water. It can only leave by evaporating, which is slower. Structural drying is about bound water.
Why measurements matter
Materials reach a natural balance with the air around them. Wood framing in a Minnesota home normally sits at a low, stable moisture level. Drying is complete when wet materials come back to the same reading as unaffected materials in the same building.
Opening windows
In a dry winter, outdoor air can help. In a humid July, open windows bring in more moisture than they let out. With dehumidifiers running, the house should stay closed.
How long it takes
Three to five days is typical for drywall and framing. Dense or thick materials take longer. See the table on our structural drying page.