Five Reasons Your Skylight Is Causing A Roof Leak

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Keeping Your Roof In Decent Shape

After listening to a few friends of mine complain about the cost of replacing their roof, I realized that I should make sure that my own roof was in decent shape. I climbed up on a ladder to see if I could see the shingles, and things weren't looking very pretty. Some patches of shingles were missing entirely, while others looked badly damaged. Fortunately, I caught the damage early enough that experts could patch up the issues. However, since roofing damage isn't always obvious, I decided to put up this website so that others can spot trouble of their own.

Five Reasons Your Skylight Is Causing A Roof Leak

10 December 2020
 Categories: , Blog


Skylights can bring natural light into your home, but they also put your roof more at risk of leaks. The following are some common causes of skylight induced roof leaks.

1. Failed Flashing

Flashing is installed around all rooftop penetrations, including skylights. These thin metal sheets create a barrier wherever shingles meet a device upon the roof. They are held down with roofing tar or another durable sealant, and the edges are usually also sealed to ensure they are leakproof. If flashing fails or isn't installed properly, your skylight may leak. A roofer will need to replace the flashing.

2. Improper Sealing

When a skylight is installed, a silicone sealant or other similar sealant is applied around the exterior edges. This sealant ensures there are no gaps between the skylight frame and your roof structure for water to seep through. If the sealant isn't applied well, it can peel, flake, crumble, or otherwise develop gaps that allow water to leak through. Your roofer can reseal the skylight properly to help alleviate these leaks.

3. Poor Roof Insulation

Sometimes the leak isn't a result of water actually breaching the roof but of condensation on and around the skylight. Generally, you need to install a skylight with insulated glass and make sure the roof is well insulated around the skylight in order to reduce condensation. Blown-in insulation in the attic around the new skylight installation may help solve this problem.

4. Shingle Damage

Installation mistakes can lead to damage to the shingles that surround the skylight. In a proper installation, the shingles are completely removed and the skylight is seated and sealed. The shingles are then replaced and properly overlapped up to the edge of the skylight. The final step is flashing over the shingles and skylight edges to create a waterproof seal. In a faulty installation, the shingles are cut through instead of removed and reinstalled as needed. These damaged shingles are left in place, which can lead to leaks.

5. Water Damming

Skylights are most prone to leaking along their upslope edge. This is because the edge acts like a dam that prevents water from flowing smoothly off the roof. Instead, the water collects along the edge of the skylight, and eventually, a leak forms. Your roofer can install a device, called a cricket, upslope of the skylight to divert water around the window. Crickets are shaped like half pyramids and are the length of the skylight's edge. Their shape splits the water flowing down the slope of the roof so it diverts to either side of the skylight.

Contact a roof repair service to address any leaks that occur around your skylight.