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Electronic Field Vector Mapping: The New Nondestructive Testing Method That Saves Time

What is Electronic Field Vector Mapping (EFVM)?

EFVM is becoming one of the most popular forms of quality control testing for architects, specifiers, contractors, manufacturers and building owners across the United States. This new nondestructive test, in accordance with ASTM D7877-14, “Standard Guide for Electronic Methods for Detecting and Locating Leaks in Waterproof Membranes,” takes half the time to locate potential holes or current leaks in new and existing roofing and waterproofing membranes than the traditional flood testing approach.

How Does EFVM Work?

Electronic Field Vector Mapping, Building Sciences, Roof Consulting

Instead of building dams around the membrane section to be tested, which can result in additional stress to the structure, EFVM testing eliminates this construction time by using voltage testing as an alternative.

Low voltage testing is performed with a conductor cable loop placed around the perimeter of the test area. A signal generator is grounded and connected to the loop cable, and the area within the loop cable is wetted. The electrical signal from the perimeter cable loop searches for an electrical path over the wet area of the roof to any breach within the wetted area, thus completing the circuit to the substrate. A sensitive voltmeter and a pair of handheld electrical probes are used to detect, measure, and track any leakage currents to the source of the breach.

High voltage testing is performed on a dry horizontal or vertical surface using a very small current at a relatively high voltage for safe testing. While one lead from the portable current generator is grounded, the other is attached to a special electrode brush made with highly conductive metal bristles. As the technician “sweeps” the brush electrode over the surface of the roof membrane, electricity will flow through any breach in the membrane. This completes the circuit between the brush and the ground, and immediately pinpoints the location of the fault.

Why Use EFVM?
  • More cost-effective approach to testing membranes
  • Repairs can be detected quickly and retested immediately
  • Overall, a more safe and efficient process than flood testing
  • Reduces the chance of possible mold growth and wet insulation
  • Can be used for ongoing maintenance, locating leaks, or warranty extensions
  • Results in better performing buildings

Matt Anderson Roofing Specialist

P: 612.369.4149