Guide
How to Find a Flat Roof Leak
The same method we use on every job, explained so you can understand what’s happening even before we arrive.
Start inside. Find the stain or damp spot and note its exact location relative to two fixed points — two interior walls, for example. This gives you a location you can translate to the roof level.
Understand that the roof-level point often isn’t directly above. On a flat roof, water travels along the underside of the membrane and along the deck before it finds a way through. A corrugated metal deck especially can carry water sideways 15–20 feet before it drips through. Learn more about this →
Check transitions first, not the open field. The large majority of leaks originate at parapet walls, flashing, penetrations, and seams — not in the middle of an intact membrane section.
Confirm before repairing. If the source isn’t obvious, moisture scanning or a controlled water test confirms it before anything gets cut into. Guessing and patching the first thing you see is how leaks come back.
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