If you’ve ever seen a skylight leak that “was repaired twice,” there’s a good chance the flashing system was never rebuilt correctly. For many skylights, the flashing kit is the real waterproofing system—not caulk, not tar, not paint.
This guide explains, in homeowner terms, what flashing kits do, why roof pitch matters, and what a correct skylight installation looks like on asphalt shingle and low-slope transitions.
What a flashing kit actually does
A flashing kit manages water using layered metal pieces (and underlayment) that direct rain around the skylight and back onto the roof surface. Think of it as a series of “channels” that keep water moving downhill.
Why roof pitch matters
- Skylights rely on gravity drainage. If the roof pitch is too low for the skylight/flashing combination, water can linger and find a path inside.
- Correct pitch selection helps prevent ponding at the top edge and corners.
Underlayment is part of the skylight system
A proper install isn’t just metal flashing. Underlayment around the opening helps manage wind-driven rain and adds a backup layer if water gets under shingles.
What a high-quality skylight install looks like
- Opening/curb is sound and correctly sized.
- Underlayment is integrated around the unit (not cut short).
- Flashing pieces are installed in the correct sequence.
- Roofing is trimmed and sealed properly around the unit without blocking water paths.
Common skylight flashing mistakes
- Skipping underlayment around the opening.
- Nailing flashing in exposed “water paths.”
- Relying on sealant instead of correct layering.
- Improper shingle cuts that channel water toward corners.
When to upgrade the skylight instead of “repairing” it
If the skylight is very old, brittle, or has failed glazing, it’s often better to replace the unit and flashing together rather than patching an aging system.
Talk to a skylight pro
For leak-free results, the details matter. See our skylight services or get an estimate. If water is actively entering, consider emergency service to reduce interior damage.