Do I need a conductive substrate for electronic integrity testing?

Yes. Both low-voltage wet testing and high-voltage dry testing require a conductive substrate directly below the waterproofing membrane — typically a concrete or metal deck. On timber decks, a conductive medium such as wire mesh or conductive glass felt can be installed during construction to enable EIT. See LRWA Guidance Note 18 (2025) for full substrate requirements.

Can you electronically test a green roof or buried waterproofing?

Not with standard EIT once the overburden is in place. For buried waterproofing, the correct method is electrical field mapping (EFM) — a buried leak location technique that locates membrane breaches to within approximately one metre without lifting the overburden. CIRIA C817 and the GRO Green Roof Code both recognise EIT as a pre-covering QA method and EFM as the post-burial investigation method.

What is the difference between moisture mapping and leak detection?

Moisture mapping tells you where moisture has accumulated within the roof build-up. It does not tell you where the membrane has failed. Leak detection methods such as low-voltage EIT or electrical field mapping locate the actual breach in the membrane. The two are complementary: moisture mapping identifies which areas need investigation; breach-location methods find the source.

Is flood testing safe for flat roofs?

Flood testing carries real risks. A 150mm head of water adds approximately 150kg per square metre of loading — structural sign-off is essential. Water can take many hours to manifest internally, making short test periods unreliable. Flood testing can also cause structural deflection that opens up laps and details. It has a legitimate role in post-repair verification of specific, structurally appropriate areas only.

What qualifications should a roof leak detection specialist hold?

Look for: NVQ Level 3 in waterproofing testing and inspection; RAWTA membership (the Roofing and Waterproofing Test Association); and a demonstrable CV in flat roofing and waterproofing systems. Under the Building Safety Act 2022, appointing an incompetent inspector carries legal liability for duty holders.

Which leak detection method works on a single ply membrane?

For QA of weld continuity at laps and details, vacuum box testing is most reliable. For field-sheet investigation with a conductive substrate, low-voltage wet EIT is standard. High-voltage dry testing also works on non-conductive single ply on conductive substrates. Black EPDM membranes are generally not suitable for EIT due to carbon black content.

How does permanent sensor monitoring differ from leak detection surveys?

Leak detection surveys are point-in-time investigations locating a breach. Permanent sensor monitoring is continuous infrastructure embedded during construction, monitoring moisture in real time and triggering automated alerts. CIRIA C817 specifies permanent monitoring for blue-green roofs; BS 6229:2025 references electronic devices for detecting leaks between inspections.

Does electronic leak detection work in the rain?

Low-voltage wet testing requires a wet surface so rain is not a problem. High-voltage dry testing requires a dry membrane and cannot be performed in wet conditions. Tramex capacitance mapping works in most weather. Infrared thermography requires dry sunny conditions. Tracer gas is best in calm dry conditions as wind disperses escaping gas.

Service

Quality Assurance

Independent inspection during installation — because most defects are decided before the roof is finished.

Why QA during installation matters

A completed flat roof looks the same whether it was installed correctly or not. The membrane is concealed beneath insulation, protection layers, drainage boards, paving or planting. Once the roof is closed up, the only way to verify what happened underneath is to take it apart again (unless you come to us for buried leak location).

A lot of waterproofing defects are workmanship failures — laps not sealed, upstands not dressed correctly, penetration details not finished to the manufacturer’s specification. These are not design failures. They are installation failures that could have been caught by someone independent watching the work at the right time.

That is what Vector’s quality assurance service provides. We attend site during the critical stages of roof waterproofing installation and carry out independent inspections — verifying that the work complies with the approved specification, the manufacturer’s technical requirements and relevant British Standards.

What we inspect

The scope of inspection is determined by the complexity of the roof and the waterproofing system specified. As a minimum, we inspect:

Substrate preparation and condition
Membrane application — laps, seams, adhesion and thickness
Upstand details, terminations and edge trims
Penetration details — pipe boots, fixings, roof outlets
Drainage falls and outlet positions
Interface details between the waterproofing and adjacent construction
Air and vapour control layer (AVCL) continuity and sealing
Insulation installation — type, thickness, orientation and fixing
Protection and separation layers

BS 6229 Section 7 requires that examination and testing (where applicable) of all layers of the flat roof build-up is carried out where necessary, including the AVCL. Our inspections are structured to meet this requirement.

When we attend

Timing is everything. We attend at the stages where defects are most commonly introduced and where the work is about to be concealed by the next layer. A typical inspection programme includes:

Pre-start review — confirming the specification matches the approved design
AVCL installation — verifying continuity, laps and sealing before insulation is laid
Membrane application — inspecting the primary waterproofing layer before protection is installed
Detail completion — checking upstands, penetrations and terminations before they are covered
Pre-handover — final walkdown confirming the completed roof before the defect liability period begins

Sensor commissioning

Where the project includes embedded moisture sensors — as part of our Complete Roof Assurance service or as a standalone monitoring installation — we commission the sensors during the QA phase. Every sensor is tested and confirmed as reporting to the monitoring platform before the roof is closed up. This eliminates the risk of burying a sensor that was never verified.

What you receive

Each inspection visit produces a written report — specific, referenced and photographic. Reports identify non-compliant work, recommended corrections and confirmation of work inspected and approved. Reports include data monitoring interpretation where sensors are installed. These reports form part of the handover documentation and provide an evidential record that the waterproofing was independently verified during construction.

Who this is for

Tier 1 contractors who want independent evidence that the waterproofing was installed correctly before they hand over the building. Developers who want assurance that the roof they are buying from their contractor will perform. Architects and engineers who need to discharge their design responsibility with confidence that the specification was followed on site.

If you are building a complex flat roof and you want someone independent watching the waterproofing installation, talk to us.

Discuss QA for your project