there is a small crack in a plasic skylight about 2 inches long.
It looks similar to an earthquake recording on paper.
Anyone know if this is a major cause of concern?
Thank you,
Glenn Helder

Skylights 101: Skylights leak.

Skylights 102: If it isn’t leaking now, it will soon enough.

Skylights 103: Refer to Skylights 101.

What was your question again??? :wink:

I write all skylights up as they are going to leak some time .
I tell the client I like sky lights but they all need constant watching and maintence . Yes the crack needs immediate repair .

Don’t know who’s putting all the skylights you folks see in but most I see here are Velux with the manufacturer’s flashing kit. It’s rare to find one leaking…some are 25-30 years old and have gone through a re-roofing with still no leaks.

I would say on average, if they don’t leak in the first year or two, they go about 12 years before problems arise.

I see aftermarket skylights leaking all the time. About the only time they don’t is when they are done during a complete tear off and re-roof. I like the Velux as well.

We have them here also…plastic domed style with plastic frame and no flashing kit. Luckily I rarely see these installed…matter of fact, I can’t remember the last one I saw!


Your description is most probably acrylic material, stress crack, and will assume started near an edge. Just like most annealed glass, the crack will continue over time to an end point. Pressure and or temperature will make it grow. It should be replaced.

Leaky sky lites! What I see is incorrect or no flashing installed. Some skylites that use rubber gasket material(push in type, versus marine glaze) tend to shrink mostly at corners and cause leaks.
When inspecting old apartment buildings that have sky lites over stairwells, generally find the old bed of glazing is completely powder and no longer effective.

The new commercial bubbles on factory’s are very good, generally made of polycarbonate(unbreakable), they shed water better and generally are raised more than 6" above roof surface.

Inspected a sky lite yesterday. Been on roof about ten years. 45 degree (12/12) pitch. The top of skylite was holding about 10 years of mud and tree debris. Pretty compact and damp. The flashing at top was not installed correct, thus not allowing proper water shed.
I could go on about sky lites. I do concur with Velux being one of the top manufacturer’s.

You can have the greatest quality product in the world, but if installed incorrectly, you may as well have purchased the cheap crap. Workmanship always dictates the quality, or lack thereof. JMHO.

Now as for saying all skylights leak is like saying all roofs leak.
There are good and bad installations, good skylights and bad skylights.
I have noticed that any crack is a deficiency.
Suspect: Skylight leakage or higher probability of leakage due to the apparent crack xx inches long.
Plastic skylights in general are a inferior product period.
If a skylight has been placed on a high pedestal and flashed properly( counter and step for shingles ) and made of glass, the life expectancy and problems of leakage lessons.
If it is plastic ( plexy glass ), and a handy man installed, there is a greater chance of leakage.
4 trades being applied.
Carpentry, roofing, window installer and tin smith.:slight_smile:
Better know more than the fundamentals.

It’s a defeciency. Funny thing is, I’ve seen many like that and not leaking, which is a puzzle to me.

Velux is tops, but any can be flashed if necessary.

And many like that leaking!

Yes indeed. It’s a coin toss! Like I say, it’s a defeciency and I always note it. It’s up to the buyer/seller duo what they want to do with it.

Frank I have installed glass skylights on BUR roofing for over 25 plus years and never a problems like Plexy or plastic.
I have installed many glass flat plain skylights on shingle roof systems and never 1 leak in 25 years that I have heard of.
The home owner that wants information ( you can not force it ) should be made aware of ALL the many products out there and PROPER INSTALLATION PROCEDURES before they make a choice.
Just my take on the subject.

I only install Velux and only when the flashing kit for it is also purchased. 30 years later, no leaks reported to me. I’d say they were installed correctly and I’d also say Velux is the best around.
I have replaced other brands with Velux and also had to replace the sheathing almpst every time. Bad skylights and bad install!

back to the original question, it’s a defect, write it up. Only a matter of time before it leaks or breaks

I shouldn’t be so brief in my answers Robert. I agree with you completely. I was speaking from an inspection standpoint. I do several a week. I point out each defeciency and give a proposal to correct, but since they’re for realestate sales, I leave it at that until either the buyer or seller call me back to do another installation.

I was talking about the cracked ones. It seems that about 50% leak and the other 50% doesn’t for some reason. My rented shop/warehouse has several broken glass ones. 1 leaks on occasion. Not an issue for me, but I like watching how things work.

Sorry I wasn’t clearer before. I hate typing.