Apprentice answer

Why is water getting under a rooftop curb counter-flashing

3rd YearRoof Curbs, Louvers & Exterior AirStop / Verify

Water behind curb flashing is a stop-and-fix condition. Verify the roofing/detail overlap, counter-flashing, sealant, and who owns the repair before the leak damages the building.

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Plain-English answer

If water is migrating under or behind counter-flashing, the issue is bigger than a bead of caulk. The curb, roofing membrane, flashing overlap, fasteners, and unit base all work together to shed water.

The recovery is to document the leak path, protect the opening, coordinate with roofing/GC, and install or revise flashing per the approved roof curb detail. Do not just smear sealant over the outside and call it fixed if water is getting behind the system.

Field checklist

Find where water enters: top lip, corners, fasteners, seams, curb base, membrane termination, or unit base.
Check approved roof curb/flashing detail and roofing scope.
Look for short flashing, missing hem, bad corner, loose fasteners, or failed sealant.
Protect the opening from rain while the fix is coordinated.
Photo before/after because roof leaks become blame magnets.

Ask Foreman

Water is getting behind the counter-flashing at [unit/location]. I traced the leak path and checked the roof detail. Do you want roofing/GC involved, or should we remake the flashing per the approved curb detail?

Verify before acting

Use this as training guidance. The foreman, approved drawings, project specs, manufacturer installation instructions, employer safety policy, and AHJ/code requirements always control the final answer.

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