Charlie Miller, P.E., Principal 7114 McCallum Street A New Leak Detection Technique Philadelphia, PA 19119 P 215-247-8784 F 215-247-4659 Charlie Miller, P.E., Roofscapes, Inc. CMILLER @ROOFMEADOW.COM WWW.ROOFMEADOW.COM Chris Eichhorn, International Leak Detection, Ltd.
Electric field vector mapping (EFVM), a new and powerful tool for improving quality
control of waterproofing systems, is now available. Although this method is unfamiliar to most Americans, it has already achieved a long record of success in Europe.
Unlike most other leak detection methods, it can quickly and accurately locate the point
of water entry. Another unique aspect of this technique is that a pinhole (too small to find visually) is as easy to locate as a large tear or failed seam. Alternative approaches, such as infrared surveys, can determine where water has accumulated in the insulation, but may
not be as useful in actually finding the waterproofing defect.
The EFVM technique uses water as the electrically conductive medium. The survey technician
installs a wire loop around the perimeter of the area to be tested and introduces an electrical
potential. The area within the loop is dampened to form an upper electrical ‘plate’. The structural
deck is the lower electrical plate, while the membrane separating the two plates acts as the
insulator. If moisture enters a defect in the membrane, an electrical contact is established
between the two plates (i.e., an electrical ground). The survey technician can then follow the 1direction of the electric field to the membrane defect.
The technique was pioneered in Germany by AB Flachdach Mess und Trocknungstechnik
GmbH (AB Flachdach) in Germany. It is now available through their North American partner,
International Leak Detection, Ltd. in Ontario, and through Roofscapes, Inc., a nation-wide green
roof provider based in Philadelphia.
The benefits of EFVM can be summarized as follows:
? Locates defects precisely, enabling efficient repairs
? Able to re-test repairs immediately
? Can be used AFTER cover systems are installed, especially with ‘green roof’ landscapes
? Less expensive than conventional flood testing
? Eliminates the hazard of overloading structural decks during testing, since ponding water
? is NOT part of the testing procedure
? Can be used on steeply sloping roof surfaces where flood testing is impossible
EFVM has been used successfully with a wide range of waterproofing materials in Germany.
AB Flachdach has electronically surveyed 35 million square feet of roof membrane in the
past five years. However, an even broader range of waterproofing materials is in use in
1Special procedures are required when using EFVM on projects with supplementary root barriers.
The root-barrier membrane will act like an insulating layer. Therefore, it is necessary to make small
incisions in the root-barrier to establish electrical contact with the underlying waterproofing membrane.
These incisions can be re-sealed after the leak is located.
?Roofscapes, Inc. 2003 EFVM
North America. The suitability of EFVM depends on the electrical resistance of the water-
proofing materials. In particular, EPDM membranes vary in their electrical properties, and some
formulations containing carbon black may not be compatible. Aluminized protective coatings,
commonly used in the US in conjunction with modified bituminous membranes, may also defeat
International Leak Detection Ltd. can conduct bench-scale tests in order to establish that EFVM
is suitable for a particular waterproofing material. EFVM can also be used on all types of roof
decks, including steel, concrete, and wood. (A special ‘grounding grid’ must be introduced in
The EFVM method has proven highly advantageous in situations where the water-
proofing is concealed or buried. These include IRMA (Inverted Roof Membrane Assembly)
configurations, plaza installations, ballasted roofs, and ‘green roofs.’ Green roofs are veneer landscapes installed on top of conventional roofs. They may be anywhere from 2.5 inches to 3
feet deep. Without an effective method of locating defects, leak location and repair could
become very expensive on these systems. For this reason, Roofscapes, Inc. offers the
EFVM technique as a standard option in its green roof installations. Currently, EFVM is being used on numerous Roofscapes projects, including Point Defiance Zoo in Washington
State, and a large chiropractic center in Pennsylvania.
A recent project in Frankfurt, Germany, illustrates the value of EFVM as a loss prevention
technique. This project involved an 110,000-square foot roof that was installed in 2000. The
technicians found 17 defects in the membrane. Some of these flaws were located in defective
seams (workmanship) but others were tiny punctures. There was no visible water damage in the
interior of the building. The building owners did not know that there were any problems and
probably would not have found the flaws until the insulation had become saturated.
For more information please contact:
? Charlie Miller at Roofscapes, Inc. (firstname.lastname@example.org), or
? Chris Eichhorn at International Leak Detection Ltd. (email@example.com).
?Roofscapes, Inc. 2003 EFVM