Skylight leak question


Based on the picture below and the location of the ceiling stains, do you think it is it improper/damaged flashing causing the leak OR is the skylight itself leaking?

Any other suggestions/ideas would be appreciated. The stain right below the skylight frame showed up last week. One roofer/skylight specialist inspected it and said all I needed to do was install new flashing to stop the leak which is less expensive to fix ($500) and another person said I needed to replace the skylight itself and add new flashing kit to stop the water leak ($1,200) - very frustrating.

Some background info: I have 3 VELUX skylights (the ones that open) in my family room which were installed when the house was built in 1988. The one farthest to the left appears to be leaking based on the location of the ceiling water damage/stains. I paid a roofer to install new roof shingles 14 months ago right after we bought the house. I don’t think there was any ceiling damage before the new roof was installed. The roofer told me recently that all skylights leak/fail after 20+ years and that to stop the leak I need to replace all my skylights. Thanks in advance for your help.



can you get a picture from outside?it looks more then just the skylite


Impossible to tell without closer inspection. Generally skylights will need to be replaced in the 20-25yr range. I would not however replace the ones that are not leaking unless they look really bad; just fix what’s broke. I would not advise changing just the flashing because to be honest most of your money is going to be spent on labor and for an extra 2-400 dollars I’d sleep well at night knowing I had a brand new unit. Even if the first guy is right and replaces just the flashing, who is to say that your seals won’t go out on your 20yr old unit 6mos from now and you’re doing the same job again… Bite the bullet and get a new unit for a few hundred more imo. If you’re in the Greenwich, CT. area I would even come look at it.


are those fixed skylights?
hard to tell the manufacturer with the blinds closed,
but from the looks of the water stain at the bottom of the casings…it looks like it’s travelling all over the drywall, and coming out at the seams.

flashing replacement kits for that size unit cost
$88.00…i roll of 6 inch vicor I&W cost $20.00.



The flashing does not go bad on a Velux. So I highly doubt it is the flashing.

The gasket around the glass is ussually the culprit.


The previous roofer who worked on the roof is the culprit.

Those are Velux VS skylights with the privacy sun shade blinds and are quite expensive, depending on the glass option chosen and the opening apparatus utilized, whether it is the crank handle or the remote control unit.

Between a $500 job for a “Maybe” repair and a full replacement for the extra $700, I would choose the new skylight due to the age alone.

Save the old one for when you put an addition on your rear deck/patio and get it flashed correctly.



I have never seen those particular style shades used on a velux unit…mostly internal shades…or a screen style. I enlarged it and looked it over and I can’t even be sure that there’s a skylight above that opening.
Either way…I agree, if a guy got paid a year ago to stop it from leaking and spent your money re-shingling the sides, two things come to mind…1…if it we me, i would have replaced the flashing kit and the shingles, not tried to jury rig a defective old flashing kit, and two…I would have tested the sash rubber before I took my staging down. But that’s just me.


By the way, based on the location of the other stains along the exterior wall, it looks like you have leaks occurring unrelated to the skylight or flashings.

If you live in an area that gets much snow and melting, I would lean towards thinking those leaks are the result of ice damming problems, which also infers a lack of 100% continuous balanced ventilation, along with the probability that the dead ended rafter bays that are blocked by the skylight(s) would or should have cross ventilation strategies included for lateral air-flow.



The skylight is fine, the problem is improper nailing of the flashing or more likely the flashing was damaged by the Roofing Contractor that installed the new roof.

If the skylight glass was leaking you would be able to see the water track down the inside of the skylight tunnel. Many times during the removal of the old layer of shingles, flashing is damaged by a careless worker and is not replaced with new flashing.

The stains directly below the tunnel trim and further down where the ceiling meets the wall suggests to me that the water is coming in through the flashing, behind the drywall, down the framing on the skylight tunnel and then down the rafter to the wall where it begins to pool and leak through the drywall.

I would go with the contractor that wants to replace the flashing ($500 is a fair price) but make sure he writes in the contract that he will replace the entire skylight flashing kit.
These flashing kits include step flashing for the sides of the skylight and a top and bottom pan.


you say you paid a roofer to install new shingles
14 months ago.
sounds like roofer did not tear off excisting roof,and
just added another layer on top.
if thats the case then that second layer probably
made the leak.
its hard to make things work when recovering roofs
without skylights.
ask roofer if thers 2 layers of shingles up there
and if there is, your probably not goin to be able
to fix. youll need to tear off everything and
start over.




I loved reading all of the informative and imaginative answers to your leak problem. Way to go guys! BUT…Being a certified Velux installer since 1985 and having been called in by Velux as an expert witness on more then a few occasions, I can tell you that properly installed Felix skylights won’t leak around the skylight itself even if there are no shingles or flashing installed! You see the key to installing a Velux is in the manufactures specifications. First, and foremost, being the underlayment. It must have all sides turned up and corner cut. Then brought all the way to the top of the skylight box and cut flush. So that when you are done all you have is 4 tiny pinholes in each corner. A little dab of mastic and those babies wont leak. Period. If we were able to have a closer look at the INSIDE of his skylight, we would find that the roofer has committed a classic Velux goof. Each flashing kit comes with it’s very own plastic bag of tiny nails, (3/4 inch). I would be willing to bet that the reroofer tossed that bag and opted instead to use his coil nailer. Must faster, but with the box being exactly 1 5/8 inch wide,his 1 1/2 inch nails + 110 psi and a high shot into the top of the flashing, combined to put a small hairline crack in the glass itself! Seen it a thousand times. So a new skylight it is. GOOD LUCK!


I always wrap all four sides of the curb with Grace Ice and Water Shield, but you gave a very critical piece of bad advice.

when applying “Mastic”, which is a generic term for roofing cement, which can come in a tube, you can not install that product in direct contact with the bituminous membrane.

The chemical solvents contained in the mastic to allow it to be viscous and easily squeezed out of a caulking gun would deteriorate the Ice and Water Shield Membrane where it was in direct contact with it.

Further, to state that even without the flashing kit to cover and protect the membrane, that it would remain water-tight is not true. The membrane would start to dry out and deteriorate from the UV rays of the sun, since the manufacturer clearly states that it should not be left uncovered for over a certain period of time. Regional sun conditions would predict how lengthy that time period would be.

Also, please look at the locations of the stains on her exterior wall. You will note that several of the spots; A) Have no continuous flowing leak stain spots from the skylight downward to the wall down the cathedral/vaulted ceiling and that, B) Several of them are not in alignment with the specific rafter bay or bays that are directly below the skylight unit itself.

Now, as a Velux authorized inspector, your job is to solve a problem, but also to limit or mitigate the amount of warranty liability to the skylight manufacturer. The high volume percentages you refer to, indicating that a cracked glass was at fault due to gun nailing in the flashings seems way out of line to me, based on my previous 31 years inspecting roofs.

All in all, most skylight leaks are due to faulty installation of the skylight flashings, especially when being re-roofed for a second time, not a stress crack in the glass.

A properly installed Velux Skylight is the best Roof window product on the market, yet often installed to minimum and below standards and specifications.



Well said Ed… I have seen plenty of skylights improperly flashed, and it is a crime when a roofer can’t get a simple flashing detail right…


I’m going to go out on a limb here…
First of all…what do you guys see that I don’t
to make you sure that there’s even a skylight behind those blinds? Speculate all you want… I don’t see handle extensions or anything to make me think that
those are venting to start with…so let’s speculate
condensation build up on the glass?, or, a venting unit that wasn’t closed, or has never closed properly, and seated itself on the rubber flanges. I have seen units
that have leaked above the membrane counter flashing when the skylight was covered with a foot of snow, and heat leaking thru the sides of the fixture melted the snow like a pond, on the top of the rear flashing piece. Open those blinds Mr. skylight owner and show us what you got!! Here’s another bit of speculation…assume that the framing cavity above the skylight wasn’t side vented to allow some air to move thru there…condensation build up above there could easily run down the back side of the drywall, showing on the bottom of the “roof window”. small spot, or continuing down the sheetrock,to cause the other stains that we see.

Another thing is…where I live, homes with electric heat are generally insulated with fibreglass insulation and then a layer of poly is stapled over the strapping…walls and roof…so, if poly is done ceiling first and over lapped upside down from the wall…there’s your water outlet.

just saying…Im betting ridge/ venting issues.


That looks like a standard case of improper flashing to me.
I will bet that the skylights are not wrapped with Ice & water shield.

The OP says that they have 3 Velux skylights and they are openers, they are also 20+ yrs old.
20yrs old is nothing for a fixed skylight but the ones that open frequently get debris on the seals, causing them to leak.
That doesn’t appear to be the case here.

Look for nails through the flashing with the top and bottom flashings being the most important.
If the flashing is not damaged it can be reused.
Remove shingles from around the skylight 2’-3’ on each side.
Remove the flashing, wrap the skylight with Ice & water shield, put it all back together.

If upon closer inspection it is determined that the skylight itself is leaking it will need to be replaced with a new unit.