How do you fix roof flashing?
First, find which flashing is failing
Flashing shows up everywhere the roof meets something: step flashing along sidewalls, apron flashing below a chimney or wall, counterflashing set into brick, valley metal, drip edge, and the flanges of pipe boots. Look for rust lines, gaps where sealant has shrunk, nails backing out, or a ceiling stain that lines up with one of these spots. In Georgia's heat, the sealant around flashing often dries out and cracks within a few summers.
The three repair levels
- Reseal: When counterflashing has pulled out of a mortar joint or reglet, clean out the joint, press the metal back, and seal it with a polyurethane or masonry rated sealant. Exposed nail heads get a dab of sealant.
- Refasten: Loose metal is renailed or screwed into solid wood, with each fastener sealed. Fasteners belong high on the metal, never in the path water takes.
- Replace: Rusted or missing step flashing means pulling back the shingles along the wall, installing new pieces one per shingle course (at least 4 inches up the wall and 4 inches onto the roof, the minimum in the International Residential Code), and relaying the shingles. Siding may have to come loose so the metal can tuck behind it.
What a lasting fix looks like
Water should hit metal and run onto the shingle below without ever depending on a sealant joint. If a bead of caulk is the only thing keeping water out, the repair will need redoing. A kickout flashing at the bottom of a roof to wall line is one of the most common missing pieces on Georgia subdivision homes, and its absence rots the siding and sheathing below.
See how roof flashing works and chimney leaks and crickets for the chimney version of this job.