Electronic Testing vs. Flood Testing
20,000 sq ft roof
Electronic Testing
(High Voltage Sweep + Low-Voltage Vector Mapping)
Fast: Often completed in under 1 day (roof clear of debris/dunnage).
Less disruption: No roofing personnel needed for HV; typically 1 person for LV.
More definitive: Tests the membrane’s watertightness by locating breaches.
More sensitive: Detects even pinhole-sized penetrations.
Future-ready: Boundary cables/screens can be left in place for quicker, lower-cost retesting.
Flood Testing
Slow: Typically 1 day to build dams and flood + 48 hours waiting to see if water appears inside.
Labor-heavy: Requires multiple roofing personnel to dam, monitor, and inspect interiors.
Less precise: Shows whether an area can hold water short-term, not necessarily that the membrane is watertight.
Can miss small leaks: 48 hours may not be enough for water from small penetrations to manifest inside.
No ongoing advantage: Provides no built-in setup for future retesting.
Case Study: Flood Testing Created the Problem It Was Meant to Prevent
At this New York city prominent Research Facility, the membrane had to be certified quickly so other trades could move forward. We were set to begin electronic low-voltage vector mapping—until a flood test was required first.
Dams were built, drains were plugged, and the roof was inundated. That night, a severe ice storm hit and temperatures dropped far below freezing. The water froze solid, turning the roof into an ice rink and bringing progress to a stop for days.
After the thaw, the flood test was declared “successful” because no water had appeared inside the building. But when we performed electronic vector mapping, we found seven membrane penetrations—and confirmed water trapped within the roofing envelope.
“We were slammed with work, so we brought someone in to perform a flood test on a project exactly as the owner had specified. They reported finding 1,500 penetrations. Then we called Roof Analyzers. Roof Analyzers came in, tested the roof properly, and proved there were fewer than 15. They were right. If it were up to me, we’d never perform another flood test.”
— Mark R., Project Manager