Skylight Leaks and Seal Failure
in Cincinnati, OH

Skylight curb flashing in Cincinnati experiences extreme thermal stress because the metal curb frame and the surrounding asphalt shingles expand and contract at different rates through the region's temperature extremes. Over time this differential movement works the step and counter-flashing away from the curb, opening gaps at the corners — where water is most likely to concentrate — and allowing rain infiltration that tracks along rafters before appearing on the interior ceiling.

The perimeter seal between the skylight glazing and its frame is a polymer gasket that degrades under prolonged UV exposure, and Cincinnati's summer UV index is high enough to cause significant gasket deterioration in older skylight units within ten to fifteen years. Once the gasket shrinks or cracks, condensation and driven rain can penetrate between the frame and glass, causing water to drip from the interior face of the unit and creating the misleading appearance of a roof leak when the problem originates in the unit itself.

During Cincinnati's freeze-thaw cycles, snowmelt or rainwater pooling on the uphill side of a skylight curb can freeze overnight and expand, forcing ice beneath the counter-flashing or under the uphill shingles at the head flashing. This ice wedging dislodges flashing components and creates a direct pathway for meltwater to enter the roof assembly without any visible gap being present when inspected during dry or warm conditions.