"Can your machine tell us exactly where the flat roof leaks?" The technician asks what is under the membrane. That is not evasiveness. Electronic leak detection depends on the roof assembly and test method, including the required conductive path. Before booking a survey, establish whether the proposed method can work on this roof.
That makes the first question surprisingly practical: what is directly beneath the membrane? A testing firm needs to know the roof assembly before promising that its equipment will answer your leak question.
Why the layer underneath matters
ELD uses an electrical path to identify a breach. The membrane and the layer immediately below it must be suitable for the selected method. Insulation separating the membrane from a metal deck can interrupt the required path; a metal deck somewhere farther down is not enough.
IIBEC's technical advisory describes the need for a conductive substrate immediately below the membrane. A compatible conductive layer can be incorporated when the roof is built. That is why testing should be discussed during design, especially before pavers or other coverings make the membrane harder to reach.
Membrane type also matters. Black EPDM needs particular attention because of its electrical properties. Some specialist arrangements can test it; a blanket claim that every method works, or that none can work, is unhelpful. Ask the testing firm and membrane manufacturer to confirm the proposed combination.
The owner points to "metal deck" in an old drawing. Mike follows the layers above it: insulation, then the membrane. The technician needs the actual assembly, not a promising word buried lower down. They request the roof records before promising what the survey will find.
A breach map and a wet-area map answer different questions
On the drawing, Mike marks a small possible entry beside a roof feature, then shades a larger area beneath it. "These are two questions." Finding and closing an opening does not establish how far moisture has spread or rehabilitate affected insulation.
Detec's explanation of ELD and moisture testing distinguishes finding membrane breaches from surveying moisture within the assembly. Our wet-insulation survey guide explains how the second question affects the repair boundary.
The reverse also matters: finding a wet patch does not identify the precise opening that fed it. The roofer may need more than one investigation method, with each report answering a defined question. Ask what decision the proposed test will change before ordering it.
A membrane breach and a wet area are different findings
In this compatible non-conductive membrane example, a breach allows an electrical path to the conductive layer immediately below. A trained tester chooses a method suited to the assembly. Locating a breach does not measure the extent of wet insulation, and a negative test does not replace other roof inspections.
Schematic view. Shows relationships, not installation dimensions.
Conditions and coverage belong in the report
Low-voltage and high-voltage methods have different surface-condition requirements. Some require a wet surface; others require a dry one. Overburden such as pavers or vegetation changes access and can limit which technique is practical. These are decisions for trained technicians, not a homeowner electrical experiment.
A useful report names the membrane, method and tested area, marks findings and identifies exclusions. "No breaches detected in the tested field membrane" is narrower than "the roof cannot leak." IIBEC also cautions that ELD does not replace visual quality control and inspection of other components.
When discussing the report, Pat asks for two separate explanations: where breaches were detected and what remains unknown about wet materials. The homeowner had expected one coloured map to settle everything. A useful survey earns its fee by making the next decision clearer, including its limits.
Plan the follow-up before the visit
Agree who will mark and repair defects, which materials will be used and how those locations will be rechecked. If a test is part of a new roof project, confirm manufacturer acceptance before installation; Carlisle's technical note illustrates why the specified conductive layer belongs in that discussion.
Before the visit is booked, the owner can now ask a better question than whether the machine finds leaks: what will this method establish on this assembly, and what will still need inspection? The answer belongs in the proposal. Nobody should need to decode the limits after paying for the survey.
