Technical Resource
LRWA GN18:2025 — Electronic Integrity Testing of Waterproofing Membranes
The UK industry guidance on electronic integrity testing
LRWA Guidance Note 18 (2025) is the Liquid Roofing and Waterproofing Association technical guidance on electronic integrity testing (EIT) of waterproofing membranes. EIT is a non-destructive testing method that uses low-voltage or high-voltage electrical pulses to detect breaches, pinholes and defects in roofing and waterproofing membranes — without removing overburden or finishes.
Why EIT changes how buried roofs are investigated
When a roof or podium deck is leaking but the membrane is concealed beneath insulation, ballast, paving or green roof systems, traditional investigation requires expensive and disruptive removal of these layers. Electronic field testing offers a precise alternative — locating the defect to within centimetres so that remedial work can be targeted rather than wholesale.
On a green roof, that difference is the difference between lifting two square metres of substrate to repair a single defect, versus lifting two hundred square metres to find one.
What GN18 covers
- Equipment specifications for low-voltage wet testing and high-voltage dry testing
- Membrane type compatibility — when each method is appropriate
- Substrate conductivity requirements
- Operator competence standards
- Reporting and documentation expectations
- QA testing prior to overburden installation
How Vector applies GN18 on live projects
Vector uses LRWA GN18-compliant electronic integrity testing routinely on complex flat roofs, podium decks and buried waterproofing systems. For buried membranes beneath overburden we extend EIT methodology with electrical field mapping (EFM) — sourced through our exclusive UK partnership with Texplor in the Netherlands — to locate breaches without removing any overburden at all.
For Tier 1 contractors handing over projects with extensive green or blue roofs, pre-commissioning EIT under GN18 is becoming a contractual requirement — both as defect prevention and as evidence of competent installation under the Building Safety Act.
Publication: LRWA GN18:2025 — Electronic Integrity Testing
Publisher: Liquid Roofing and Waterproofing Association