Are you worried that your skylight is leaking and causing hidden damage to your roof? Have you already tried resealing your skylight, only to find that the leak keeps coming back no matter what you do?
At RoofSmart, we install and replace around 1,000 skylights every year. Before every roofing job, we perform a thorough inspection of the roof and the areas surrounding it to make sure that we find all roof issues and their causes.
This helps us to accurately identify the cause of skylight leaks and take the necessary precautions to make sure that everything is fixed, including hidden problems that might be causing leaks.
In this article, you’ll learn :
- The signs your skylight is leaking
- What causes a skylight to leak
- What areas of the skylight commonly leak
- How to avoid leaks in your skylight
By the end of this article, you’ll be able to tell what’s causing your skylight to leak based on where it’s leaking and know how to prevent leaks in the future .
Quick Answers
In Seattle’s rainy climate, a leaking skylight is often more than just a bad seal. It’s a warning sign of improper roof installation or hidden structural rot. Most leaks occur at either the lower end (indicating a failed glass-to-frame seal) or the higher end (indicating faulty flashing or uphill roof issues).
To prevent costly water damage, RoofSmart recommends a technical inspection to determine if you need a simple flashing repair or a full deck-mounted replacement before the moisture compromises your roof deck.
What are the signs my skylight is leaking?
Here are the things to look for that indicate that your skylight is leaking :
- Condensation or water collecting on the glass
- Water stains on the ceiling around the skylight
- Drip marks around the skylight
Sometimes the water stains and drip marks are faint or don’t appear for a while . If you notice these issues it means that either the flashing needs to be replaced or the entire skylight needs to be replaced.
Repairing flashing on a curb-mounted skylight is fairly easy because the skylight sits above the roof, but replacing a deck-mounted skylight is more difficult because it sits in the roof.
What causes a skylight to leak?
Noticing that your skylight is leaking can be alarming. It’s important to understand what is causing the skylight to leak so that the appropriate fix can be made .
With that in mind, here are the different reasons why your skylight might be leaking:
1.) The skylight itself is damaged or compromised
Skylights can be tricky because sometimes they shift a little bit or get damaged but there are no obvious signs that something is wrong (until you spot the leak).
If something hits your skylight, it might not have been a strong enough impact to damage it, but it can still warp it or cause it to shift. The impact can put stress on the joint where the skylight is connected to the frame and break the seal.
It’s also possible that the skylight contracted or expanded due to temperature changes. Most modern skylights are designed to handle this, but sometimes extreme weather can cause extra harm .
Typically, deck-mounted skylights are more susceptible to leaks and warping issues because they’re bound in place within the roof. On the other hand, curb-mounted skylights handle size fluctuations better because they can shift within their frame above the roof (as long as there’s a good seal around them it should be fine).
2.) The flashing around the skylight isn’t working properly
Flashing issues can happen for many different reasons. The most common issue is improper or poor installation practices . It could be that the spacing is incorrect, or perhaps the installer ran out of the proper material and used something else as a substitute.
Sometimes, the top layer of flashing doesn’t come out far enough, so water can easily get into the gaps. If the skylight is old, the flashing might be worn out.
3.) There is a leak somewhere else but it appears in the skylight
Sometimes the roof is leaking and it’s completely unrelated to the skylight, but the skylight happens to be the closest access point for water to get into the roof .
There can be any number of causes for this, but it can typically be traced back to improper installation practices or a leak coming from something on your roof that is worn out or damaged (like the chimney, a pipe boot, or a vent).
What areas of the skylight commonly leak?
Water can potentially get in from anywhere around the skylight. But looking at where the water appears can indicate what the cause of the leak is. Skylights are angled downwards in line with the pitch of your roof, meaning that gravity has a big impact on how water enters around it .
This provides two main entry points: the lower and higher end of the skylight .
- Lower end of skylight: I f the water is coming in around the lower end of the shingle it’s probably the skylight itself leaking (the seal between the glass and skylight frame) . The leaking water is contained within the skylight, but it only shows up when the water hits the lowest part of the skylight.
- Higher end of skylight: Another potential scenario is having water leak through the higher end of the skylight. This means that there is an issue with the flashing or there is a leak somewhere higher up on the roof. Water entering through the top end comes from elsewhere and goes into the skylight because it’s the first entry point in the roof that the water hits. If there was a leak inside the skylight, it would run down further and enter through the lower end of the skylight instead.
How can I avoid skylight leaks?
A lot of people think that skylights will inevitably leak and there’s nothing that can be done about it. However, this is not true. The real problem stems from installation issues or other issues in the roof .
If you want to install a skylight but you’re hesitant because you don’t want issues with leaks, then we recommend doing research to find a contractor who is experienced in installing skylights .
To keep your roof in good condition, make sure you perform regular maintenance on it and repair it as needed. Bring in a roofing contractor to inspect the roof if you have concerns or help you with upkeep. This is the best way to avoid issues with your skylight or other areas of the roof down the road.
Need help finding an experienced, reliable contractor? Check out our Qualified Roofer Checklist to learn what questions to ask your roofer to evaluate their qualifications:
What do I do next if my skylight is leaking?
Dealing with skylight leaks can be difficult and frustrating, but knowing what is causing the problem can help give you peace of mind. Carefully examining where the water appears in your skylight can tell you if the problem is with your skylight or if you need to look elsewhere on the roof.
To help you determine the cause of the leak and help you prevent issues in the future, you can bring in an experienced roofing contractor. In addition to fixing your skylight leak, they can assist with maintenance or annual inspections to keep your roof at its best.
Now that you know what’s causing your skylight leak, you’re probably concerned about the next steps you can take to prevent further damage and higher repair costs. Check out our article “What Should I Do If My Skylight Is Leaking?” for an in-depth guide on identifying skylight leaks and making the necessary repairs.
Want to see how we'd look at your roof?
Start with a SmartMatch™ Needs Analysis, or call (206) 487-4877.
Frequently Asked Questions
What are the first signs that my skylight is actually leaking?
Common indicators include condensation or water pooling on the glass, water stains on the ceiling drywall, or faint drip marks around the interior frame. If you notice these, the moisture has likely already bypassed the primary barrier and is affecting your roof's integrity.
Why do skylights leak even after being resealed?
Resealing is often a "band-aid" fix. If the leak is caused by warped frames from temperature fluctuations or improper flashing installation, topical sealant won't hold. Professional replacement of the flashing or the entire unit is usually required for a permanent fix.
What is the difference between a deck-mounted and curb-mounted skylight leak?
Deck-mounted skylights sit flush within the roof and are more prone to leaks if the roof shifts or warps. Curb-mounted skylights sit on a raised frame; while they handle thermal expansion better, they can leak if the seal between the "cap" and the curb fails.
Can a roof leak look like a skylight leak?
Yes. Because a skylight is a physical opening in the roof, water from a leak higher up (like a damaged chimney or pipe boot) will often travel down the rafters and exit at the skylight, making it look like the skylight is the culprit when the source is actually elsewhere.
How does gravity help diagnose where a skylight leak is coming from?
If water enters at the lower end, the seal between the glass and the frame is likely broken. If water enters at the higher end, the issue is almost always the metal flashing or a leak originating further up the roofline.
Why is skylight maintenance especially important in the Pacific Northwest?
Seattle’s constant moisture means that a small flashing gap can lead to rapid wood rot and mold. Regular inspections ensure that debris isn't trapping water against the seals and that the flashing hasn't been compromised by our frequent windstorms.
How can I tell if a roofer’s quote for a skylight repair is fair?
Pricing can vary wildly based on whether a contractor is doing a simple "patch" or a full code-compliant replacement. To protect your budget, review our guide on what red flags to look for when comparing roof proposals.
What should I do if I find mold around my skylight during a repair?
Mold is a serious indicator of long-term moisture entrapment. Before you agree to an expensive remediation, learn how to tell if your attic mold is actually a problem or just a surface issue.
Could poor ventilation be making my skylight "leak" through condensation?
Sometimes "leaks" are actually extreme condensation caused by trapped humidity. This is common in homes with improper airflow; see our breakdown on whether a Seattle attic can be over-ventilated to understand the balance.
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