How is roof flashing done for solar panels?
Short answer. Solar panels are attached with mounts bolted into the rafters or deck, and each penetration should be protected by a flashed mount: a metal or composite flashing plate that slides under the shingle course above and over the one below, with a sealing collar or gasket around the fastener. Mounts that rely only on sealant under a bracket, with no flashing, are a common source of solar leaks.
How flashed mounts work
- The installer locates a rafter, or uses a deck-mounted system rated for the decking, and drills a pilot hole.
- Sealant goes into the hole and under the base.
- A flashing plate slides under the shingle course above and lies over the course below, the same way a pipe boot does.
- The lag bolt or screws pass through a raised boss or gasketed collar on the flashing, so water running down the roof never reaches the hole.
- The rail attaches to the mount above the flashing.
Red flags
- Brackets screwed straight through shingles with only a dab of sealant.
- Flashing plates laid on top of the shingles above instead of tucked under them.
- Shingles cracked while being lifted to slide flashing in, especially on older roofs.
- Conduit supports fastened through the roof without flashing, and wire penetrations without a boot.
- Mounts placed in valleys or other high-water areas.
Roof first, panels second
Panels typically stay up for decades, and removing and reinstalling them to replace a roof later adds cost and coordination. If the shingles are more than about halfway through their expected life, replacing the roof before installing solar is usually cheaper overall. Ask the solar installer whether its workmanship warranty covers the roof penetrations, and how later roof work affects that coverage.
Permits and fire access
Rooftop solar is permitted locally and must meet the code's structural and fire access requirements, including clear pathways on the roof for firefighters. Your city or county building department handles the permit. See replacing your roof before solar and roof flashing explained, or Robust Roofing's guide to solar panels and roof replacement.