How to Seal a Leaking Skylight Window

A small skylight lets natural light shine in from the ceiling.
  • 3-5 hours
  • Beginner
  • $40-130
What You'll Need
Clear silicone caulk
Weather stripping
Safety gloves
Roofing tar

A leaking skylight window is no joke. Apart from water getting inside your house and all over your floor, there’s also the problem of additional strain on the ceiling and walls as well as the possibility of mold. Check out the steps below so you can find the leak and get it taken care of as soon as possible.

Note: Before you fix the leak you need to verify that it is not just condensation. This occurs frequently in rooms like kitchens or bathrooms or in colder weather conditions or climates, especially where the skylight window is just a single-pane glass installation. If the leak only happens at certain times of the year, the cause might not be the actual window itself. During winter, it could be due to ice or snow blocking water from draining down the roof and causing it to run under the shingles around the skylight instead.

Step 1 - Inspect the Skylight

After inspecting the inside of the skylight, use a ladder to climb onto the roof to check the outside. Move any leaves and debris from around the window, and once it is clear, check for any cracks in the cover and look at the weather stripping (it should be firm and free of signs of cracking). After that, look at the flashing for lifted or torn seams and small holes. Finally, see if there are any lifted or missing shingles around the perimeter.

Step 2 - Replace the Weather Stripping

Unscrew the fasteners holding the cover of the skylight window on with an appropriately sized driver. Then, lift it off and keep it to one side. With a scraper, slowly remove the weather stripping around the skylight cover and the curb. Take a moment to seal any cracks you find on the cover with the clear silicon caulk. Run a bead along the entire length of the crack then spread it evenly with your fingertip.

Next, put new weather stripping on the curb of the skylight window. Start on the downward slope and push firmly all around the edge to secure it in place.

Step 3 - Apply Tar

Put on a pair of thick work gloves to protect your hands and begin spreading roofing tar around the curb of the window with your trowel. When you are doing this, be sure to cover the outside walls of the skylight, paying special attention to the corners or any holes in the metal or wood. You should spread the tar about eight inches in all directions, taking care that you lift any loose shingles and put tar underneath them to stick them down. The roofing tar should run around the top of the shingles as well.

Step 4 - Finish Off

Run a bead of the clear silicone caulk so it sits between the weather stripping and the outside of the curb. Now, put the skylight cover back on the window. Before you replace the screws, dab a drop of silicone into each of the screw holes. Replace the screws, but be careful not to tighten them too much. Add more caulk over the screw heads, and rub some over any cracks on the outside of the cover.

These steps should take care of any leaks from your skylight window. However, while you're up on the roof, you should also inspect the entire thing for any other damage, and carry out any remedial work before problems get progressively worse.