How to Seal Skylights

Whenever you install a skylight in a roof, you must make sure there is no space left from where the skylight can cause a leakage. You must ensure that the skylight and the surrounding area is completely sealed and there is no room for any kind of contaminant or any other thing, such as rain water, to come down. You should be really careful when applying the roof cement on the edges of the shingles that surround the skylights.

Apart from newly installed skylights, old ones can also require sealing process. The wear and tear can make the edges of the skylights damaged, which can cause the leakage. Therefore, you should be really careful, when it comes to properly applying the roof cement, to seal the skylight. Otherwise, you may have to bear the consequences, in the form of extra expenditure on repairing.

Moreover, you should not contact any professional to seal the skylight installed. In fact, you can do it yourself, if you have the basic know-how about the structure of the skylight and its surrounding areas. It is really simple to apply the seal and you can definitely save cost that you may incur by hiring a professional.


  • 1

    Expose the skylight’s flashing:

    Remove all the shingles that are parallel to the perimeter of the skylight. It will allow you to see the skylight’s flashing clearly, where you will apply the seal.

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  • 2

    Applying Cement:

    Apply the cement where the skylight’s flashing meets the roof. Using a medium-size putty knife, create a 1/4-inch thick layer of the cement around the skylight. Also apply the cement underneath the shingles that you removed from the side of the skylight earlier. Place them back from where you removed them and press them softly, so that they can grip the roof.

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  • 3

    Sealing the Skylights:

    Now apply more cement to the edges of the shingles, which are intersecting with the next shingles in place. Make sure that the space between the edges is completely sealed with the roof cement. Now place the cement at the edges of the shingles, which are joining with the skylight. It is advised that you should pay extra attention to the shingles that are placed above the base of the skylight. You must carefully fill the space between the shingle and the skylight, in order to proper seal them.

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