How to Diagnose a Leaky Skylight

Skylights provide an excellent source of natural light and warmth to your home. They are available in a variety of styles and require different flashing systems to achieve a watertight seal in your roof. As can be expected, some skylights will leak, and if left to persist this problem can cause damage to your roof, ceiling and flooring below. Homeowners frequently discover they have a skylight leak when there is a puddle of water on the floor beneath it. If this happens to you, do a little investigating to find the real source of the drip.


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    Look to see if there is a water stain around the skylight unit or in the skylight tunnel. If the water stain is near the top of the skylight (the edge nearest the peak of your roof), there is a good chance the flashing on your roof around the skylight is failing. Water may be running down your roof and finding its way between the shingles and skylight and into your home. Even if the flashing on your skylight is intact and working properly, if other pipes or vents above the skylight have compromised flashing, the water could be entering your roof there, then running down and leaking through your skylight opening.
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    If you do see signs of a leak at the top of your skylight, call a roofing professional to inspect the flashing on your roof. It is not recommended to replace the flashing yourself - especially using a quick application of tar - as this can cause more damage.
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    If you spot a water stain near the bottom of your skylight you may have more of a condensation issue than an actual leak. Condensation can form on the inside of your skylight when there is a lot of humidity in your house (which can be trapped by a skylight tunnel) or when it’s very cold outside. To keep condensation from dripping, most skylights have a condensation channel surrounding the edges that captures it and allows it to evaporate. When too much condensation fills up the channel it can overflow and drip on the floor. If you discover a water stain at the bottom of your skylight and a roofing contractor has inspected your flashing, have him take a look at your condensation channel.


  • A skylight leak can cause minimal damage in the short term, but over time the damage can become significant. If you think the drips coming from your skylight are just condensation it is very important to be sure, as an actual leak can cause serious structural damage to your roof if left to prevail.

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Categories: Doors and Windows