A valley collects water from two roof slopes and concentrates it at the outlet. If that flow reaches a low-slope roof, both the valley and the receiving membrane detail need inspection.

What to check first

  • Remove debris that diverts the flow.
  • Check the valley outlet and adjoining wall.
  • Inspect the overlap into the low-slope roofing system.

Follow the connection from top to bottom

  1. Find the upper entry point

    Inspect where flashing ends against a wall, curb, pipe, or other surface. Water entering behind that termination may bypass a patch lower down.

  2. Correct the underlying defect

    Loose metal, rotten wood, failed fasteners, and deteriorated membrane need a suitable repair before waterproofing. A surface bridge needs stable, compatible material on both sides.

  3. Keep the detail functional

    A repair should shed water without blocking outlets, weep paths, or intended movement. Use the specified reinforcement and dimensions for the product and detail.

From the project archive

flat-roof-valley-flashing - Valley areas are prone to leak due to the lack of using proper materials
Historical project photo · Flat Roof Doctor
When two panels meet to form a valley, care must be taken to secure the area
Historical project photo · Flat Roof Doctor
flat-roof-valley-flashing - When workers walk on a roof they always find the easiest way up or area to secure themselves
Historical project photo · Flat Roof Doctor

Product reference: Bergstrom Industries’ published knowledge catalog. Follow the latest product label and safety information. Historical project examples are educational and are not a specification for every roof.