How to Seal a Leaking Skylight Window

A leaking skylight window is no joke. Apart from water on the floor, there’s also the problem of additional strain on the ceiling and the walls as well as the possibility of mold. Before you fix the leak, you need to verify that it really is a leak and not just condensation. This can occur 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 of the skylight. Move any leaves and debris from around the skylight window. Once the window is clear, check the window cover to any cracks 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.

Step 2 - Replacing the Weather Stripping

Using a screwdriver, unscrew the screws holding on the cover of the skylight window. Lift off the cover and keep it to one side. With the scraper, slowly remove the weather stripping around the skylight cover and the curb. If you find any cracks on the cover, seal them with the clear silicon caulk. On the inside of the cover, 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 of the window.

Step 3 - Applying Tar

Using your trowel, spread roofing tar around the curb of the skylight window. When you are doing this, be sure to cover the outside walls of the skylight window paying special attention to the corners or any holes in the metal or wood. You should spread the tar about 8 inches in all directions from the skylight window, 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.

Step 4 - Finishing 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 screw, dab a drop of silicone into each of the screw holes. Replace the screws, being careful not to tighten them too much. Put caulk over the screw heads and rub silicone over any cracks on the outside of the skylight window cover. These steps will take care of any leaks from your skylight window. While you're up on the roof, you should also inspect it for any other damage and carry out any remedial work before problems get progressively worse.