How to Repair or Replace Damaged Roof Flashing

F flashing acts as the primary defense against water intrusion at the most vulnerable points of your roof, such as chimneys, vents, and valleys. When metal shifts or seals crack, water finds a path directly into your roof deck, leading to rot and expensive interior damage that often goes unnoticed until a ceiling stain appears. Performing this repair requires a keen eye for detail and strict adherence to safety protocols. A job done well results in a seamless, watertight seal that directs water away from your home's structural components. Expect to spend your time carefully prying up shingles to maintain the integrity of the surrounding roofing material while securing the new metal.

  1. Find the leak source first. Locate the source of the leak by checking the area directly above the signs of interior moisture. Carefully lift the shingles surrounding the damaged flashing using a flat pry bar to expose the underlying metal.
  2. Extract the old metal. Extract the nails holding the old flashing in place with a nail puller. Slide the damaged piece out from under the shingles, taking care not to tear the surrounding roofing felt.
  3. Bare the deck completely. Scrape away all residual roofing cement, rust flakes, and debris from the wood sheathing. Ensure the surface is completely dry and free of grit before proceeding with the new installation.
  4. Cut and test-fit precisely. Measure the area and cut your new flashing to size using heavy-duty tin snips. Ensure the piece overlaps the shingles below it while sliding well underneath the shingles above it to maintain a proper shingle-style water shed.
  5. Lock down with cement. Apply a generous bead of high-grade roofing cement under the edges of the flashing. Nail the flashing into place, keeping the nail heads covered by the shingles whenever possible.
  6. Reseal the shingles down. Slide the existing shingles back into their original positions. Apply small amounts of roofing adhesive under the corners of the shingles to keep them flat and wind-resistant.