Bad skylight? HELP! Can't figure this one out

Did a 5:12 total re-roof, teardown to bare wood (older, has 5/8" deck) with vaulting underneath & horizontal decorative boxed in beams.

Customer selected two locations for skylights right up @ the ridge line.

These were the Velux QVM Manual Venting Skylight (the crank pushes out a chain that stiffens to push the pane out; no angled bar like on an old school crank window).

This thing has leaked 3x now & I can’t figure out why - all I can think is it’s the skylight. The leak appears interior (obviously…) @ the BOTTOM of the skylight where it connects with the horizontal beam.

I have checked the seal on the glass where it connects withthe metal framing & there was a bad turn on something related to the crank; it was slightly mooshing the rubber seal, but IMO not enough to warrant a water pen.

The skylight on the Western slope does NOT leak; this one is on the E side & in this area of Texas, less than 5% of our rain & higher winds come from.

The customer said that each time, when we have had a torrential rain, there hasn’t been a leak apparent, however when we have had light rain, the roof HAS leaked.

We’ve removed shingles in all areas around the skylight & have yet to see any moisture on the roof deck; this is a self flashing curb mount style & we’ve sealed it up in all areas, even added a bead along the glass to metal connection on the outside of the skylight.

The lack of roof deck moisture tells me it’s either the flashing to roof deck joint or a bad skylight. The water ONLY becomes visible @ the bottom of the skylight (& yes, the customer said he did a leakdown test).

I’m @ a loss here.


Well if these were new skylights then it could be the seals on the one or a flashing mistake. I try and steer clear of opening skylights as much as i can for those reasons. Why did they want them so close to the ridge? Could the rear curb be damaged from the ridge? Or not sitting flush since it is at an angle? If it was me i would reflash the enitre skylight and if it still leaks then i would deam it a bad seal. But thats what i would do. You really have no choice but to fix it. Also i know this is a no brainer but when a light rain is going on go over there and see where it is leaking from. I had 1 pin hole in a rear curb and this thing leaked like the titanic. Replaced the curb and all was well. Hope this helps Ranch. Let me know how it works it self out.

What is the room below the leaky light used for?

This room is the ‘family’ room of sorts; it’s where they have their big screen TV (on the W side)… there’s nothing under where the leak drops out other than a leather couch & tile floor. So far, the couch seems to have shed the water nicely, thankfully.

They had to go so high in the slope due to the beams (non functional / decorative) on the inside of the ceiling (that’s the black N / S bar I drew in there). I may take a digital photo when we go back over there…

A big head scratcher is why does it leak ONLY on light rain & not on heavy?

Any thoughts on condensation causing it to leak? I have the Velux rep’s phone # & might put in a call to him.

& While I know I’m getting ahead of myself here, but if it was YOUR project & you did 4 repairs & it turned out the whole time it was the skylight… would you charge for anything you’ve done in the past? So far, it’s been about 8 trips to & from / picking up his shingles plus labor. Parts are 35 Yr Atlas, 1 roll of 15 #, 4 tubes of GeoCel 2300, 3 gallons of Henry & about 2 bundles in product for tear off & re-shingle.

  • Note: I didn’t really want to put the skylights in this location anyhow…

Is it the glazing seal leaking? Most of the commercially available sealants do not work on glass very well without a primer. Well, they will for a while, but glass is to smooth to hold the long term bond of the bead.

HAve you dis-assembled the skylight to find the entrypoint of the water? This will tell you definitively where the leaks are occurring…or if it is condensation.

I have had skylights that would “leak” only in a light rain, but it was actually part of the metal flashing was exposed on the inside due to a lack of finish work inside the tunnel. This seemed to cause the “leak” in a light rain.

I think because the barometric pressure is sitting at the dew point and causing condensation, and in t storms, it drops below dewpoint it rapidly, and no condensing of the moisture. That might be 100% wrong, too. Who knows? :smiley:

Hi Gtp1003,

The flashing and the skylight are one piece. You can not flash it wrong.

If you nail the shingles through the flashing then the flashing will leak.


The gasket on the glass is leaking.

Install a new skylight.

I think because the barometric pressure is sitting at the dew point and causing condensation, and in t storms, it drops below dewpoint it rapidly, and no condensing of the moisture. That might be 100% wrong, too. Who knows? :D[/quote]

I was going to suggest that it might be a condensation problem as well, it has happened to me.

NOt all of them are one piece lefty, i have seen several that are not. I know if you nail thru them they will leak. I was just asking.

Hi Gtp1003,

He stated that it is a self flashing unit.

i believe these are the units w/neoprene(cant think of right name) flashing similar to WASCOs E-class skylights,i put sealant under the perimeter of the flashing 1st,then usually the gasket is secured w/ hot dipped galvanized roof nails,if this has all been done,then lefty is probably right about the skylight glass leaking,but in the event it is,you should see evidence of that-fog inside or interior of insulated glass streaking,from the description of the leak(dropping straight to the couch from the opening)i would also suspect the glass—btw-wheres the photos ranch-less guessing that way :wink:

Lefty is more than likely right. I can not find where it said 1 piece flashing but i dont have my glasses on right now. Eitther way i would replace the skylight and see if that works.

You could replace the glazing seals. Thats pretty easy to do. If the glass is steamed between the panes, then that is a different matter completely.

No condensation between the panels.

No nails through the flashing (there are + shaped spots to secure it; I used deck mates).

I will post pics soon; having two kids under 2½ years old + a wife that works doesn’t allow for me to always do things on the schedule I’d like.

Thanks for all your input.

Now, if only I could get some of y’all over to my “shed / how would you do it” question :arrow::arrow::arrow::arrow:


The ones I run into the glass does not get wet.

It looks like a roof leak. Sometimes the wood frame is stained. But not always.

RanchHandRoofing, I know the following has nothing to do with your problem.

Skylights are a real pain.

We have the customer sign a waiver if they do not replace the skylight. This states that if there is a leak within 3 feet of the skylight we are not responsible.

If a new skylight leaked on me. I might have them sign a wavier for new skylights too.

Thanks, Lefty…

Now, back to mowing the lawn. I’m going over tomorrow & peeling up shingles in about 1 square all the way around it & we’ll see what the deck looks like.

Oh, yeah… photos. Gimme a sec or two to upload to my PhotoBucket account. :mrgreen:

I hate skylights, and in my efforts to ensure they don’t leak I take special care when working around them or when installing new ones. Can’t tell you how to fix you problem though.

But after the second or third trip I would have been calling the sky light rep to come and ok to have a new skylight put in. If you removed all the shingles, and reflashed the skylight and it continued to leak; I’d have to say it was the skylight. Any more trips would be at a cost of which I’d hit the skylight company up for.

Awwwwwwright… here they is.