Building Moisture Intrusion

The location and timing of wetting, piping layout, weather history, moisture patterns, plumbing use, leak- or pressure-test results, and condition of exterior assemblies can be compared when evaluating possible sources. Wetting that repeatedly coincides with rainfall may support an exterior-entry hypothesis, while moisture associated with fixture use or pressurized piping may support a plumbing-related explanation. Because water can migrate through cavities and along building components before becoming visible, the location of staining or damage does not necessarily identify the original entry point.

Condensation can develop when moisture-laden air reaches a surface or location within an assembly that is at or below the dew-point temperature for the surrounding air. Exterior water intrusion involves liquid water entering through an opening, joint, penetration, flashing condition, or other water-management pathway. Temperature and relative-humidity data, air-barrier and insulation conditions, pressure relationships, weather history, staining patterns, and testing can help assess which mechanism is more consistent with the observed moisture.

Elevated moisture readings, staining, material swelling, corrosion, deteriorated finishes, odors, damaged insulation, or changes around penetrations and joints can indicate possible concealed wetting. Borescopes, selective openings, and other investigative methods may provide direct information about concealed spaces. Infrared thermography can identify thermal patterns that warrant closer investigation, but those patterns do not directly prove moisture or locate its source and should be confirmed with appropriate measurements and physical evidence.