Unlike most other leak detection methods, ELD can locate the point of water entry without disturbing the roof assembly. 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. Additionally, when the membrane is applied directly to a structural surface (parking garage, roof deck, ramp, bridge, etc.) thermal anomalies are not present but ELD still detects membrane faults. FSA owns both high voltage and low voltage ELD equipment.
Low Voltage ELD
Low voltage testing uses a small amount of 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 direction of the electric field to the membrane defect.
High Voltage ELD
High voltage testing is performed using a small, high voltage current on a horizontal or vertical dry surface. A portable generator contains two leads, where one lead is grounded to the roof deck and the other is attached to a brush made with conductive metal bristles. The survey technician sweeps the deck looking for defects. If there is a breach the current will flow through the hole completing the circuit.
Benefits To Our Clients
- Locates defects precisely, enabling efficient repairs
- Able to re-test repairs immediately
- Less expensive than conventional flood testing
- High voltage can be used on steeply sloping roof surfaces where flood testing is not possible
- Eliminates the hazard of overloading structural decks during testing, since ponding water is not part of the testing procedure
- Low voltage has proven highly effective in situations where the water-proofing is concealed or buried, such as protected membranes, ballasted roofs, and ‘green roofs’.