Primary and Secondary Damage following a Water Intrusion

3/29/2019 (Permalink)

Water intrusions will affect building materials both immediately and over time. Damage that occurs immediately by direct contact with water is referred to as primary damage. Damage that occurs because material remains wet for an extended period of time is referred to as secondary damage.

Water also affects materials indirectly. Excessive moisture leads to elevated humidity. Many building materials will absorb excess water vapor and suffer damage, especially when the air in the structure is allowed to remain above 60% relative humidity. This form of damage from high humidity is also referred to as secondary damage. Secondary damage includes dimensional changes, loss of structural integrity, microbial growth and staining.

Hygroscopic materials absorb moisture easily, whether from direct contact with water or from exposure to high humidity. As a result, hygroscopic materials are very susceptible to secondary damage. Such materials gain and lose moisture continually in an effort to equalize with the water content in the surrounding air. The more hygroscopic the material, the faster it will collect water vapor, and the easier it will suffer secondary damage.