The transition between a shingle roof and a low-slope membrane must direct water onto the lower roof. Water can travel beneath the shingles or through an incomplete transition even when the flat membrane appears intact.

What to check first

  • Inspect the uphill transition and any valleys feeding it.
  • Check whether the materials are suitable for the slope.
  • Look for concealed decay before covering the joint.

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-repair-leak - What compounded the problem on this roof is that there was a skylight.
Historical project photo · Flat Roof Doctor
The pitch of this roof is to low to even try to make a repair.
Historical project photo · Flat Roof Doctor
flat-roof-repair-leak - The design of this roof is also bad. When you see a corner of a skylight flashing in a valley
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.