Water Leaks in a Skylight

Examination

• Inspecting your skylight can help you determine the most likely source of dripping water. Standing beneath your skylight allows you to look upward and find the highest point of an existing water stain. A water stain that starts near the highest point of a skylight usually indicates a problem on the surface of the roof, while a water stain that begins closer to the ceiling than the roof is a common sign of a problem with the skylight unit.

Roof Repair

• A roofing contractor can repair any missing or broken shingles that surround the outer surface of the skylight. The main purpose of the flashing around the outside edges of the skylight is to redirect the water away from the opening. However, forceful rain can drive the moisture against the flashing on the high side of the unit, causing the moisture to spray backwards and seep between the adjoining shingles. Resealing the exterior of the unit between the shingles and flange area can help eliminate this type of leakage. Premium flashing cements work well for this purpose.

Fit

• Incorrect installation that results in a poor fitting skylight is a common cause of leaks around the unit. These leaks often start appearing in the center portion of the skylight and along the lower edges that extend through the surface of the ceiling. A rubber gasket between the surface of the roof and the outside edge of the skylight unit can help seal off the moisture.

Condensation

• A less obvious cause of leaky skylights comes from condensation, rather than outside precipitation. Condensation is most likely to occur when the temperature inside the house is much cooler or warmer than the outside air. Condensation may build up around the inside of the unit and seep into the ceiling. Installing ceiling insulation in the air gap between the unit and the attic space will help eliminate this condition.