The Challenges Associated with Inspecting Skylights

Roof with skylights.

Deck-mounted skylights such as these are not as leak-resistant as curb-mounted skylights.

Homeowners love skylights because they let so much extra light into the room. But builders — and especially roofers — love them less, because they are, after all, holes in the roof.

Proper installation cuts down on the chances of leaking, but eventually, all skylights leak. To be fair, eventually, all roofs leak as well, since materials wear out. But skylights tend to leak sooner than most roofs.

As a building inspector, what should you keep an eye out for with skylights?

Look for Leaks and Signs of Water Damage

Leaks and water damage are the main problems with skylights. If possible, inspect the skylight from both the inside and the outside.

Skylights may be curb mounted or deck mounted. If they are curb-mounted, this means they sit in a sort of frame or box that juts a few inches out from the roof. Deck-mounted skylights appear flatter and more in line with the roof. Many builders consider deck mounting inferior to curb mounting, but uninformed homeowners may choose the former because of their appearance.

Regardless of the type of mount, both should have adequate flashing that’s in good condition. If a skylight fails and a new one is needed, it is easier and cheaper to install if the original was deck mounted, because it may not be necessary to replace the flashing.

Ice Damming on Curb Mounts

If the flashing looks good, check the top edge of the skylight for any signs of damage or rot. Especially with a curb-mounted skylight, snow can collect here and form an ice dam, causing water to eventually penetrate the roof.

While you are inspecting the exterior skylight, look for signs of repair like caulking or roofing cement. These fixes are temporary and inadequate.

Also look for signs of water damage indoors on the ceiling or in the attic, such as mold, wet or pulpy wood, or bubbling or discolored paint.

Skylight frame with mold.

This skylight is moldy due to condensation problems.

Foggy Skylight Glass

Also, check the glass for clarity. Glass that appears foggy may indicate a compromised seal. Many skylights are insulated with a layer of argon gas in between the panes, like windows in the home. Once this seal is broken and the gas escapes, moisture may penetrate the panes, fogging the glass.

Another culprit is age, especially with plastic panes. These can get scratched over time more easily than glass, obstructing the view. UV rays can also cause skylights to look cloudy or splotchy. This problem isn’t as serious as a leak, but still may be noted.

Sometimes condensation will form on the skylight glass. If the installer skipped the step of adding insulating felt, this could make the problem worse, causing the warm air in the room to come into contact with the cold air outside in the winter. This allows condensation to form on the inside of the glass and potentially drip into the interiors.

This problem is often mistaken for a leak. While it is not technically a leak, it’s still water dripping in the home, so it should be repaired.

ICA’s home inspection courses can teach you everything you need to know about inspecting homes, including skylights. To learn more about our home inspection courses, check out our website today.

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