Water, water everywhere

Flood testing is appropriate only for waterproofing systems

There are various occasions when roof system specifications call for flood testing, such as to determine quality assurance of a newly installed roof system or locate a leak source. But sometimes, flood testing is recommended when it isn't appropriate. Following is a discussion about NRCA's guidelines for flood testing.

Not recommended

NRCA does not recommend conducting flood tests as part of a routine quality-control or quality-assurance program for a new roof system. One reason is flood tests sometimes are solely and incorrectly relied on to determine roof system quality. Flood testing alone does not forecast a properly designed or installed roof system. For example, a flood test will not provide information about service life or evaluate a roof system's ability to resist wind or impact loads.

Flood testing also is not appropriate for identifying potential leak sources. Roof systems are designed to be weatherproof, not waterproof. A weatherproof roof resists the passage of water with a minimal amount of hydrostatic pressure (flowing water); waterproofing systems prevent the passage of water under hydrostatic pressure (standing water). For example, water leakage may occur at roof drain flashings with flood testing. Flood testing exposes roof drains to hydrostatic pressure, and roof drains are not designed to be leak-free under such unrealistic imposed conditions.