Skylight leak repair questions & answers.

This article series explains how to find the cause of skylight leaks and other sloped glazing leaks.

Our photo at page top of a leaky roof skylight that has suffered repeated and non-durable repair attempts using roofing cement.

Skylight Repair Leak Repair Q&A

Question: many big skylights leak: we want to install a roof over the whole shebang

Larry and Kathy Boso said:

We have a roof that has 16 double 5x8 windows. The leak during rain and they leaks are in different places.

We have tried fixing all of them, but decided to just put a roof over them all. Our delema is, how to put a roof over them. We are thinking about a free staind roof.

Cant put any weight on the windowed roof. Each window weighs 200lbs? It would cost an arm and a leg to get a crane operater to lift out the windows. Afraid of the whole roof colapsing. Any ideas? Help?

Reply:

L&K

Wow what a dramatic fix for leaky roof windows. I understand the frustration. But before you decide on the roof-over option there are some considerations that lead to a bottom line: you need help from a design professional and from your local building department. Concerns include:

1. Even with a roof over, unless the edges are enclosed on all sides, blowing rain may still cause leaks at the skylights.

2. Special construction, perhaps trusses, would be needed to bear on the ridge and eaves walls to span over the existing roof.

3. With a "double roof" construction there may be fire safety and fire code issues. Firefighters don't want to have to chop through multiple roofs if fighting a fire.

4. Ultimately the cost of the roof over project, done properly, may lead to a different approach: eliminating most of the 16 double roof windows in the existing roof, replacing any roof windows to be kept with curbed units with proper flashing, and then re-roofing that surface.

Use our email found at our CONTACT link to send me some photos and I may be able to commnent further.

Question: risks associated with skylights

Hi and thanks so much for all this info!

My question relates to the risks associated with skylights. I am in the U.S. at the moment but lived in Denmark the last 8 years and there, you see skylights on almost every house. I am helping a friend get a new roof on her log cabin, and want to strongly recommend skylights.

I know Velux has had excellent flashing that go with their windows and he slope is good. She has spoken with others (men, actually, whereas I am female but have a lot of experience with construction) and three have told her not to install skylights.

Her house is so dark that even in summer if you want to see anything in detail, you have to turn lights on during the day ($$).

Assuming that one buys proper windows and uses highly capable contractors to install them when a new roof is being put on, do you think there is a substantial risk of failure down the line or think perhaps the people she spoke with were referring to window failures from the days when they were installed improperly, at a bad time (i.e. over the roof versus with the roof) or were less effectively designed products? Thank you for your response! - (June 2, 2014) Jen W-C said:

Reply:

Thanks for the question, Jen.

I don't know who the men are with whom your friend has spoken but it sounds like a lot of bluffing and arm-waving to me.

Modern skylight products have evolved significantly from early (leaky) products.

The manufacturers have a great interest in the success of their product, and to that end have designed raised curbs that bring the skylight above the roof surface, and pre-packaged roof flashing components that are very reliable and leak-proof if the installer follows the manufacturer's installation instructions.

The people with whom she was speaking could be

1. remembering the older products from 30+ years ago that were not so well designed

2. confusing indoor condensation with roof leaks

3. people who installed skylights willy-nilly without using the proper components nor reading the installation instructions. I was talking with such a builder about a leak on a home he had just finished constructing.

"They all leak like that" he said, as if that meant it was OK. Well he was right, all of his houses leaked at that point because he built them all the same way - with the flashing installed backwards. Some builders know construction. Others are better at arranging financing.

Jen

Please also see

inspectapedia.com/BestPractices/Skylight_Installation_Procedures.php

on skylight flashing.

The skylights shown there were installed in a truss-roofed cabin in Northern Minnesota, in a climate exposed to severe weather at the edge of Lake Superior. They don't leak.

Shown also on that page are the older "low profile" "bubble" type skylights that didn't have such a great success record.

 

On 2020-09-21 by Ellen Rollings What's causing this skylight leak?

Just noticed this stain today, definitely on top of the drywall and not coming from within. Is this likely to be a leak from the glass? It looks similar to one of the example photos on this page.

I’m not sure if the trickle stain is coming from under to wood trim or over it.

Ellen,

Reply by mod

That leak stain could be at the flashing or it could be an overflow from a condensate tray found at the lower end of some skylights.

Your cover prevents us from seeing enough of the window to be confident that we know what's going on.

Perhaps you can post another image with that spring-rod and cover put aside.

On 2017-11-12 by Eric - leaky rectangular bubble skylight

I have a leaky rectangular bubble skylight that has developed leaks in the 2nd floor bathroom. seems to be coming from the high point corners. should i use roof repair caulk or what do u recommend? thanks

On 2017-11-26 - by (mod) -

You may be able to make a temporary repair working from the roof surface using flashing cement or even clear silicone caulk.

But what would be most productive would be a very careful inspection to find the exact reason for the leak such as damaged loose missing or incomplete flashing.

If you can safely access your ruview best hire a roofing repair contractor.

On 2016-07-28 by Lisa

What is the purpose of a curb when a skylight is installed on a low pitched roof? Is the curb just to raise the skylight to allow for rain possibly not draining off the roof quickly? Or is the curb supposed to add pitch so that the skylight itself is pitched more than the roof, allowing water to run off the skylight quicker?

Very confused since I see examples of both pitched curbs and curbs that are equal height all around.

On 2016-07-30 - by (mod) -

No, Lisa. The curb allows installation of flashing around the perimeter of the skylight at the intersection of skylight edges and roof surface.

Without that flashing the skylight would leak like mad into the roof structure and into the building below; flashing around any roof penetration (skylight, chimney, plumbing vent) is of critical importance. For a time in the 1970's a nearly-flat skylight was popular, was almost impossible to seal satisfactorily, and was a notorious leak source.

On 2016-04-08 by Anne

My skylight is a smaller version of the first one on your post. There's a wood beam in the middle on the inside of my apartment that gets wet from outside when it rains. I can feel an obvious breeze from it and I can hear everything outside, even cars and sirens passing by.

I have no access to the roof.. Is there any way I can repair it from inside? The manager of my apartment refuses to get it fixed professionally.

On 2016-04-08 - by (mod) -

Anne:

Probably not. Sealing the inside of any leaking roof component is likely to drive the leaking water horizontally into other roof components. Almost always, a roof leak needs to be repaired from outside, on the roof surface.

 

Question: is it condensation or a leaky skylight

(June 23, 2011) catherine said:

my skylight drips when it rains , I am not sure if it is condensation or a leak , the skylight is on my sun roof , it is a slightly raised slanted hardtop roof

Reply: If the skylight drips ONLY when it rains

If the skylight drips ONLY when it rains I suspect there is a leak in the roof flashing around the unit, or in the skylight itself. Try spraying water up on your sunroof in warm dry weather and see if you can reproduce the condition.

Be careful about on-roof inspections on sunroofs as you don't want to damage other sunroof panels (nor slide off and fall).

Question: protective film to stop skylight leaks?

July 18, 2011) Jean said:

HIOw's about if the skylight itself has a leak? does a protective film would be useful to stop such a leak?

Reply:

I don't think a protective film on skylights is going to do much to stop most skylight leaks, Jean. Most skylights leak at their surrounding flashing. Skylight films are plastic coatings applied to the glass.

Question: why is skylight leaking after new roof?

(Sept 1, 2012) Anonymous said:

skylight leaks and I wonder why? New roof put over the old roof and the the gap between the new roof and the skylight is now much less, would that cause a leak, the 3 leaking skylights are operable and the one non leaking skylight is in operable. When I leave the skylights open a crack they do not leak

Reply:

I can't diagnose this or even speculate from just the information in your note. Check for improper flashing around the skylights or failing to even install flashing when the new roof was installed.

Question: leaks at skylight during hurricane

(Oct 30, 2012) Todd said:

skylight just started to leak from lower corner, huricane sandy hitting western Pa as of now. could this be from rain blowing, condensation from colder air, or acuall leak

Reply:

Probably a leak

Question: light penetration around skylight - is this a leak?

(May 27, 2014) Debbie said:

What does light penetration into the attic mean in regards to a skylight?

Reply:

Debbie I think what we're talking about is inspecting in an attic for points that may be leaking. Sometimes (not always) if you look up at a roof from inside an attic and see daylight, that's a hole or a leak point.

The reason I say not always is because light may be reflected indirectly up-roof through flashed openings or between wood shingles or slates nailed over spaced sheathing boards.

When you see a point of light or "a thousand points of light" in your roof, look there for water leak stains as well as checking the floor surface below that area for leak marks.

 

 

Question: skylight leak sealant

(June 13, 2014) Gail said:

my skylight is leaking around the wood part of the skylight. what can i use on this to seal it

Reply:

Clean the surfaces and try a silicone sealant

 

 

 

Thank you to our readers for their generous comments

(June 23, 2011) Debbie G. said: Very helpful info. Thanks!

...

Continue reading at SKYLIGHT LEAK DIAGNOSIS & REPAIR - topic home, or select a topic from the closely-related articles below, or see the complete ARTICLE INDEX.

Or see SKYLIGHT LEAK DIAGNOSIS & REPAIR FAQs - questions and answers posted originally on this page

Or see these

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• SKYLIGHT LEAK DIAGNOSIS & REPAIR
• SKYLIGHT LEAK TROUBLESHOOTING
• SKYLIGHT VENTILATION DETAILS
• WINDOWS & DOORS

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