Reasons for Leaking Skylights – Family Roofing

Posted on by David Reid

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Reasons for Leaking Skylights

Skylights are meant to let in extra light, not water.  Added natural sunlight makes your home feel brighter and more spacious, but leaking skylights can take all that beauty away and replace it with rotting structures or mold if you don’t catch them in time.  Skylights are a great architectural design element that can let natural light into an otherwise dark room. Because they penetrate the roof’s surface, skylights can sometimes leak.  Leaks are commonly caused by worn weatherstripping, holes around the flashing and older skylights that have begun to fail. If you notice a leak from your skylight, the first thing you need to do is identify where the water’s coming from.

If you notice a small amount of water leaking out of your skylights, there are several simple ways to troubleshoot and potentially repair the leak.

1. Double check to make sure that the skylight is fully closed.  Obvious but worth a try.

2. Verify that the leak is not actually pooled condensation on the underside of the glass.  This happens often — in very cold climates, in humid rooms, and with single-glazed skylights. To reduce condensation, add insulation between the framing members and the skylight itself.  The easiest solution is expanding spray foam.

3. Look at the area around the skylight from both inside and outside (using proper safety precautions) to check for damp or stained surfaces.

4. Clear away any leaves, twigs, and dirt that have gathered on the skylight and check the glass itself for cracks.  Seal skylight cracks with a layer of clear silicone along the entire length.

Your roofer can determine if, indeed, your skylight is leaking or the water is coming from some other source.  Below are possible reasons why skylights or the surrounding roof could be leaking into your home:

  1. A wandering roof leak — Your skylight sits within your roof’s field shingles (or metal panels), and all around it, your roof extends up to the ridge and down to the eaves; a ridge leak can wander down between your roof layers before dripping through drywall near your skylight.

  2. The skylight itself — Sometimes the skylight frame (metal or wood) loses its structural integrity, and small amounts of moisture can bead up, then drip down into your living space.

  3. Condensation — The skylight could be entirely watertight, but the sun can cause condenstion to form on the inside of the glass, then pool and drip inside your home.

  4. Faulty installation — Roofers are best equipped to install skylights, although handymen and do-it-yourselfers will claim expertise, faulty installation is extremely common and often doesn’t reveal itself for years, as materials degrade and gaps open up.

  5. Failed flashing or weakened roof cement — Flashing is thin metal used to bridge and seal gaps between unlike materials, such as the skylight and the roof sheathing.  Roof cement is a sticky adhesive used to hold parts in place.  If either fails, your skylight can leak.

  6. Improperly installed insulation — Every gap and space within the walls and roof of your home should carry insulation to keep your expensively treated indoor air indoo.  Poor or missing insulation allows water to accumulate and enter your home.

Inspect the Roofing and Flashing Around a Leaking Skylight

Once you’re sure the water is penetrating from the roof outside, look carefully to see if the shingles and flashing around the skylight are properly installed and functional.  Roofing should be firmly nailed down, so repair any lifted shingles.

Next, take a look at the flashing.  Because the purpose of flashing is to make a watertight seal between the skylight and the roof, any visible defects or damage (like corrosion or pinholes) are signs your flashing needs to be replaced.  You should also check that the roofing material extends all the way around the flashing, including each side and the top.  If there is space between the roofing and flashing, water can get trapped and cause leaks.

Seal Flashing Around a Leaking Skylight

Start by clearing any water or debris that has collected between the roofing and flashing.  Then lift the roof shingles away from the edges of the skylight so you can access the flashing.  Use a putty knife to add a layer of roofing cement in the gap between the edge of the flashing and the roofing.  This will provide a seal against future leaks, as long as it doesn’t dry out or become brittle.  Check the roofing cement sealant every few months. If it’s peeling or dried out, remove and apply a new layer.

When the flashing itself is damaged or moldy, it must be replaced.

Condensation

While you’re examining the skylight, look for signs of condensation on the glass.  If you find any, you’ll probably notice it collects at certain points and drips from there.  The best remedy for condensation is ventilation.  If the skylight doesn’t open, consider using a fan to improve air circulation.  It’s also recommends going on the roof and clearing obstructions from the weep holes, the tiny holes on the lower part of the skylight frame that allow condensation to drain. This will prevent the skylight glass from clouding up.

Faulty skylight

If the skylight opens, check the rubber gasket around the frame for signs of deterioration or mold.  That would indicate the skylight isn’t sealing all the way and moisture is dripping between the window casing and the frame.  To remedy this, you may need to replace the gasket. You may also find bits of debris preventing the skylight from closing all the way. Removing them may stop the leak.

Your inspection may reveal moisture around a cracked section of the skylight.  Although it may be possible to remove the cracked part and repair it, in most cases you’ll have to replace the entire skylight.

If you determine the water is indeed coming from the flashing, the next step is to call a professional to have it repaired correctly.

Faulty roof flashing

Once you’ve eliminated condensation and skylight defects, any water you see must be coming through the roof.  It’s either seeping under the flashing or getting through the seal between the flashing and the skylight.

If it’s coming from the frame on the upper part of the roof slope, that’s easier to diagnose and repair than if it’s coming from the lower part of the frame.  Water tends to travel along the roof decking, so a leak from the lower part could originate from anywhere on the roof.  One from the upper part is almost always from the skylight flashing.

The best way to diagnose the true cause of water infiltrating around or near a skylight is to contact a professional roofer.   After a complete inspection, your roofer can give you remedies for the real issue (skylight, roof, insulation, condensation, etc.) and save you money on needless “repairs.”