Why is my roof leaking from the solar panels?
Short answer. Most leaks on solar roofs come from the holes made to install the array: lag-bolted mounts sealed with caulk instead of flashed, conduit and junction box penetrations, and lags that missed a rafter. Others come from the roof under the panels wearing out, debris trapped behind the array, or an ordinary flashing failure that happens to sit near the panels.
Where solar leaks start
- Mounts: each rail foot is bolted through the shingles into a rafter. Mounts with a metal flashing slid under the shingle above are reliable; mounts that depend only on sealant under the foot can leak once that sealant ages.
- Missed rafters: a lag that misses the framing gets pulled and reset, sometimes leaving a sealed-over hole that opens later.
- Conduit and junction boxes: wiring that passes through the roof deck needs its own flashed penetration.
- Old shingles under the array: panels are built to last 25 years or more, but a roof that was already 10 or 15 years old at install will wear out first, and the panels hide its decline.
- Debris and pests: leaves and pine needles collect under the array and hold water against the shingles, and squirrels and birds nest underneath and chew wiring and shingles.
Tracking it down
Start in the attic on a dry day right after rain. Look for stains around lag bolts from below, wet decking and drips running along rafters. Measure from a gable wall or a vent so the spot can be found on top. A leak below the array is not always caused by the array, so check pipe boots and valleys nearby too.
Who to call
Read your solar contract first. Many installers warranty their roof penetrations for a set period, and letting another trade open the array can affect that warranty. If the problem is the roofing itself, the panels may need to come off and go back on for a proper repair. If the roof is near the end of its life, read why to replace the roof before solar and common roof leak causes.