High Voltage Roof Membrane Test
The holiday detector dry test, delivered independently
Hi-Volt Survey™ is our high voltage electronic integrity test for flat roof membranes.
Often referred to as a holiday detector test or a spark test, the high voltage dry test identifies breaches, pinholes and discontinuities in exposed membrane systems, carried out in dry conditions across suitable flat and low-pitched roofs.
Using calibrated holiday detection equipment, we sweep the exposed membrane surface to identify breaches, pinholes, punctures, discontinuities and installation defects, the small failures that a visual inspection can’t see but that will let water into the roof if left unfound.
We’re independent roof surveyors. We don’t carry out repairs, so our findings reflect the condition of your membrane and nothing else.
Dry Test or Wet Test?
Hi-Volt Survey™ is one of two electronic leak detection methods we provide:
Hi-Volt Survey™ high voltage (This page)
high voltage, dry conditions. Fastest coverage of exposed membranes; the standard choice for handover and quality control testing.
Scan-Map™ low voltage (Wet Test)
low voltage, wet conditions. Traces current back to the point of water entry; the stronger choice when an active leak needs its source found.
Not sure which applies? We’ll recommend the right method before anything is booked.
Call 0845 257 7663
How the holiday detector test works
The test passes a controlled high voltage across the membrane surface using a brush or broom electrode, with the roof deck (or a conductive layer beneath the membrane) earthed. Where the membrane is intact, no current flows. Where there’s a breach, even a pinhole, the circuit completes, the equipment signals the defect, and its position is marked and recorded.
Because the method is electrical rather than visual, it finds what the eye can’t. Defects measured in millimetres, hidden within laps, or sitting in details that look perfectly sound from above.
The test is carried out in dry conditions on a dry membrane, which is what makes it fast. Large exposed roof areas can be swept systematically without waiting for rainfall or wetting down the surface, so it’s well suited to programme-critical moments like handover.
Pinholes
Defects small enough to be invisible to the eye still break the waterproofing layer. High voltage testing finds them because the probe reacts to the breach, not to how large it looks.
Punctures
Dropped tools, foot traffic, follow-on trades and installation damage all leave holes in the membrane. Testing locates them precisely so the repair is a patch rather than a strip-up.
Splits & tears
Thermal movement, stress at fixed points and handling damage open the membrane over time. The survey records where the split runs and how far it extends.
Open laps & failed welds
Seams are the most common failure point on a welded membrane. A lap that looks sound from above can still be unsealed along part of its length, and testing shows exactly which section.
Discontinuities in the waterproofing layer
Any break in continuity across the tested area is located and logged, including defects concealed beneath surface dirt, chalking or weathering.
Defects at penetrations
Vents, outlets, soil pipes, cable entries, plant fixings and support feet are checked individually. These details carry a disproportionate share of roof failures because each one is a hand-formed junction.
Weaknesses at upstands, edges and transitions
Corners, kerbs, changes in level, expansion joints and interfaces with other systems are all tested. Where two things meet is where membranes usually fail.
Damage from later works
Solar PV installation, plant replacement, safety line fitting and maintenance access all risk breaching a membrane after handover. Testing establishes whether they have.
Confirmation of intact areas
Just as useful as finding defects: where the membrane tests clean, you have documented evidence that it’s sound, which matters for handover, warranty and dispute resolution.
Our Roof Survey & Leak Detection Services
Electronic Leak Detection
Non-destructive moisture mapping helps locate hidden moisture within the roof build-up and understand the extent of the problem. This supports targeted repairs and better maintenance decisions.
High Voltage Dry Test
A high-voltage integrity test carried out on dry, exposed membranes, identifying pinholes, punctures, discontinuities and workmanship defects across the membrane surface.
Earth Leakage Wet Test
Carried out in wet conditions during rainfall or after the test area has been wetted down. This method traces the direction of current flow back to the point where moisture is entering the membrane. That makes it the strongest choice when a leak is active and its source needs finding.
Scan-Map™ and EPDM Testing
A faster low voltage wet method, and the one that opens up membranes the others can’t reach. Conventional electronic testing relies on the membrane being non-conductive, which rules out EPDM entirely. Scan-Map™ tests it.
Membrane Condition Surveys
Independent electronic leak detection and integrity testing for flat roof and waterproofing membranes. Ideal for identifying breaches, pinholes, punctures, installation defects and membrane failures on new or existing roof systems.
Thermal Imaging Leak Detection
Thermal imaging roof surveys help identify saturated insulation, entrapped moisture and areas of concern that may not be visible during a standard inspection. A useful method for predictive maintenance and roof condition assessment.
Moisture Mapping
Non-destructive moisture mapping helps locate hidden moisture within the roof build-up and understand the extent of the problem. This supports targeted repairs and better maintenance decisions.
R.A.I.N.™ Roof Monitoring
R.A.I.N.™ is Surveyroof’s roof monitoring and early warning service framework, supporting continuous insight into roof condition using sensor-based monitoring technology. It helps detect moisture and roof incidents earlier, particularly where ongoing visibility is important.
Visual Condition Surveys
Detailed visual roof condition surveys with photographic reporting for industrial metal roofs, aluminium standing seam, pitched tiled roofs and other roof areas where a clear condition report is needed.
Roof Maintenance Programmes
Planned roof maintenance surveys designed to help extend roof life, reduce unplanned costs and identify issues before they develop into larger failures.
Pre Installation Solar Surveys
Planned roof maintenance surveys designed to help extend roof life, reduce unplanned costs and identify issues before they develop into larger failures.
Industrial Roof Surveys
Independent industrial roof surveys and inspections for factories, manufacturing plants, warehouses, industrial estates, processing facilities and logistics operators across the UK.
Commercial Roof Surveys
Independent commercial roof surveys and inspections across the UK for property owners, facilities managers, managing agents, retailers, hoteliers, logistics operators and solar installers.