Not every roof leak needs sophisticated equipment. Some need a torch and twenty years of knowing where to look. Here’s how a competent investigation actually works — in order.
Step 1: Start with the common suspects
Eliminate the likely before testing the unlikely.
- Terminations. Membrane should turn up adjacent walls a minimum of 150 mm. Sealant joints fail. Check them first.
- Penetrations. Pipes, drains, outlets, fixings, balustrade posts. Every penetration is a potential failure point.
- Cover flashings, cappings, copings. Mortar bedding fails. Pointing fails. Lead lifts.
A case study: an inverted hot-melt roof leaks twice. The temptation is to commission buried leak location, flood-test the membrane, escalate the equipment. The actual answer was a perimeter detail. Not the membrane. Twenty minutes with a competent eye saved two weeks of survey work.
Step 2: Consider the build-up before choosing a method
The right test follows the construction, not the other way round.
- Accessible membrane, wet conditions — wet electrode (low-voltage) testing
- Dry, exposed, on a conductive substrate — high-voltage dry testing
- Buried — green, blue, ballast — the only viable non-destructive method is buried leak location with Texplor’s EFM technology
- Non-conductive build-ups — moisture mapping with a Tramex Dec Scanner as first pass
If the build-up cannot be confirmed from drawings, confirm it from a core. Do not test what you cannot describe.
Step 3: Think about the design — not just the membrane
A surprising proportion of “membrane failures” are actually design failures the membrane cannot save you from.
- Falls. Field, gutters, valleys, outlets. Standing water on a roof that was specified to drain.
- Standing water. Mud curling at the edges is the membrane telling you it has been wet for months.
- Door thresholds. Insulation height versus upstand height. Get this wrong and the doormat is the lowest point of the building.
- Sumps and overflows. Missing or undersized.
- Blue roof insulation flotation. Designed-in pondage that wasn’t restrained properly.
Most of this can be caught at RIBA Stage 3 via Vector’s Waterproofing Design Review. All of it is harder and more expensive to catch once the roof is built.
Step 4: Do not trust what has already been done
The reason we get called in after three failed investigations is that the first three trusted their predecessors. Repeat the tests. Verify the previous repairs. Assume nothing.
What experience actually buys you
- Andy Flood spent his career in flat roofing. His father was a flat roofing contractor. He has seen what fails before it fails.
- Ben Hickman was a contributing author on CIRIA C817 (blue roofs) and on the BS 8102:2022 revision, and gives expert evidence on waterproofing disputes.
Twenty years of pattern recognition is not replaceable by any test on the market.
Talk to Vector about your investigation, or read about buried leak location.