Flat Roof Leak Repair
On a low-slope roof the stain inside is almost never below the hole. Water runs across the deck and finds a seam, a fastener or a joint, so locating the source is most of the work.
Where single-ply roofs leak
- Seams — especially a cold weld, where the heat or pressure was insufficient at install
- Drain bowls, where the clamping ring has loosened or the membrane has pulled
- Curb flashings around HVAC units, the single most common source we find
- Pipe boots, whose sealant has a far shorter life than the membrane
- Parapet and wall terminations, where counterflashing or termination bar has failed
- Mechanical fasteners backing out and backing up through the membrane
How we find it
Visual inspection of every detail first, because most leaks are at a detail. Then flood or spray testing in sections to confirm before anything is cut. On roofs with suspected saturated insulation, an infrared scan after sundown shows where heat is still held by wet material.
We do not smear mastic over a stain's ceiling location and call it repaired.
Repair versus replace
An isolated detail failure on an otherwise sound membrane is a repair. Widespread seam failure, saturated insulation across large areas, or a membrane at end of life is a replacement, and patching it repeatedly costs more over three years than doing it once.
We will tell you which one you have and show you the evidence.
Common questions
Can a flat roof be repaired in the rain?
An emergency measure can stop active water entry, but a proper welded repair needs a clean, dry substrate. We stabilise in the wet and return to repair properly in the dry.
Why does my roof leak only in heavy rain?
Usually drainage rather than membrane failure. In light rain the water leaves before it reaches the weak detail; in heavy rain it backs up at an undersized or blocked drain and rises above a flashing.