Structural Moisture

Structural moisture refers to the moisture content present within building materials and assemblies. All building materials contain some moisture, and managing this moisture is essential for the building's durability and indoor air quality. Sources of structural moisture include construction moisture (water used in concrete, mortar, and plaster), use-phase moisture (from indoor activities, bathing, cooking), and external moisture (rain, groundwater, and soil moisture).

Concrete is a particularly significant source of construction moisture. A typical concrete floor slab can contain 100 to 200 liters of water per cubic meter when cast, and this moisture must be allowed to dry before moisture-sensitive floor finishes (vinyl, wood, carpet) are installed. If finishes are applied too early, the trapped moisture causes adhesive failure, flooring damage, and can promote mold growth beneath the surface.

Structural moisture is measured using various methods including pin-type resistance meters (for wood), capacitance meters (for non-invasive screening), and relative humidity probes (for concrete). A professional moisture survey uses these instruments systematically to map moisture levels throughout a building, identify abnormal readings, and determine whether moisture levels are within acceptable limits for the materials and conditions present.

Controlling structural moisture requires a whole-building approach: proper waterproofing below grade, effective vapor barriers in the envelope, adequate ventilation to remove use-phase moisture, and sufficient drying time for construction moisture. If moisture levels are found to be elevated, the source must be identified and addressed before cosmetic repairs are made. Attempting to seal in moisture with impermeable finishes only traps the problem and makes it worse.