How To Fix a Leaking Skylight

Do you have a skylight that is leaking?

There are a multitude of different designs and materials used in skylights. The most common by far around San Antonio is the acrylic dome skylight on an aluminum base. When these leak, typically, the homeowner notices some drips on the floor or furnishings beneath the skylight during and after rain showers. This progresses to staining and bubbling paint on the drywall directly below the skylight. The damage is usually apparent on the down slope side of the skylight. Often, the leak inside the home is accompanied by leaking behind the drywall and into the attic. If caught early, it’s usually a straight fix on the skylight. If let go, the damage can be expensive to repair and can involve replacing rafters, roof trusses, drywall and insulation.

Typically, the do-it-yourself homeowner, believing the leak to be originating from around the acrylic dome, will climb on the roof with a tube of exterior caulk and seal around the acrylic dome where the retaining frame locks the acrylic dome to the base. However, often the problem is not at the dome. The problem more often than not lies beneath the shingles where the base of the skylight sits on the roof decking.

Applying caulk around the edge of the acrylic dome does nothing to fix the leak.

A combination of old shingles and old mastic or caulk used to seat the skylight on installation (or re-installation after shingle replacement) provides avenues for the water to enter the home. Often during rain, the water running down the roof will dam slightly on the upslope side of the skylight. From here, a small proportion of the water will seep in under the shingles and find a route under the mastic. Once it gets between the skylight base and the decking, the water finds its way down the roof slope via the sides of the skylight and then makes its appearance on the down slope side.

Fixing the leak requires removal of the skylight. The skylight can be reused and reseated, but usually the acrylic is old and brittle and the better option is to simply take measurements in advance and have a new, replacement skylight ready to replace the old skylight when it is removed.

Acrylic dome skylights are quick and cheap to manufacture and simple to install. They are typically comprised of an aluminum base, two acrylic domes and a retaining ring that holds the domes in place over the base. The base has an integral gutter that both supports the edges of the domes and sheds water on the inside of the domes out onto the roof. On installation, mastic or caulk is applied to the base flange and then the base is nailed or screwed into place. More mastic is applied on the upper surface of the base flange and shingles are sealed down over the base flange. Leak protection is afforded by the mastic only.

Velux skylights are more expensive, but the leak protection, insulation qualities, light transmittance, strength, expected longevity and quality are vastly superior.

If you don’t want to fix it yourself, call us at Solar Texas. We’ll be glad to fix it for you.