The Skylight Is Leaking From Heavy Rain

Flashing Function

• Often roof leaks originating from a skylight are from a poor seal between the skylight’s flashing and the roof’s shingles. The flashing is piece of metal that attaches to the skylight’s base and inserts under the roof shingles that sit above the skylight. If the skylight rises above the surface of the roof, it may have flashing up the sides and on the edges where the skylight’s sides meet the top. Normally the flashing offers a watertight barrier over the area the skylight penetrates the roof, keeping the water on the roof and out of the attic.

Reasons for Leaks

• A skylight’s flashing may leak for several reasons, which determine what you must do to stop the leaking. The metal flashing may be rusting or corroding at certain points, opening up holes that introduce water into the house. A slight amount of damage on the flashing, such as a bent or split corner also allows water to leak inside. Sometimes the person who originally installed the skylight did not place the flashing below the shingles that sit above the skylight, and over the shingles that sit below the skylight. Using nails instead of screws to secure the flashing may result in leaks, since the nails may pop out of the roof over time.

New Flashing

• If you find damaged or corroded flashing, install a replacement. Use a small pry bar to help lift up the shingles that sit over the old flashing, allowing access to the nails or screws that secure the flashing to the roof. Peel away any roofing tar that sits on the edges of the flashing and then lift the flashing up and off the skylight. Install the new flashing under the shingles above the skylight and over the shingles below it to shed water, using screws to keep the flashing firmly against the roof. Seal all nail heads with roofing tar or caulk to prevent water from entering there.

Condensation

• The skylight may appear to leak water on cold, rainy days when no moisture is making its way past the skylight’s flashing. Poor insulation between the skylight and the roof’s framing leads to condensation around the skylight. As the condensation gathers, it drips down and hits the ceiling or walls below. Spraying insulation into the gaps between the skylight and the framing should insulate the skylight enough to stop future condensation from accumulating.