Polycarbonate skylights.

[Poe34]

Hey guys, I had this metal roof replaced about 5 years ago and I have a leak from this skylight. I went up to take a look, and am curious if this is installed correctly. The material is very brittle and is cracked where the screws were installed and that's where it is leaking from.

 

[Rusted Nut]

The material is very brittle and is cracked where the screws were installed and that's where it is leaking from.

Pretty typical for polycarbonate, unfortunately.

 

[RoninB4]

+1 for above post

 

[Uncle murph]

Hey guys, I had this metal roof replaced about 5 years ago and I have a leak from this skylight. I went up to take a look, and am curious if this is installed correctly. The material is very brittle and is cracked where the screws were installed and that's where it is leaking from.

In my experience it’s installed no different than the metal which I believe is incorrect. The good news is that it is easily replaced.

 

[MovingAlong]

Check with the manufacturer about the installation instructions for those panels.

 

[mikedodge]

Thsts about how long they last. Ususlly once I've seen mine are cracking I put clear Gorilla tape on them then go out and get new ones.

 

[rlitman]

Pretty typical for polycarbonate, unfortunately.

5 years is way too short a lifetime for that. I've had Suntuf roofs on sheds for about 15 years now, and none have gone brittle yet.

Polycarbonate is VERY UV sensitive. They get around this by applying a UV protective coating to the top surface of it. In the OP's case, you can't really install it upside down, but with Suntuf, that would be a big mistake, so you need to be careful.

Two things come to mind. Perhaps the UV coating was damaged or defective. That's all that would make it brittle, and once it gets hazed and goes brittle, it's trash. But there is also one important installation note that if not followed can lead to early failure.

Polycarbonate thermally expands quite a bit. You're supposed to drill oversized holes and then drive the screws down to the point that the neoprene coated washer is in contact, but the rubber isn't very squeezed out. The polycarbonate should have the ability to move a bit under the washer. If it's trapped, that can lead to cracking.

edit: Looking back over the OP's pictures one more time, I'm leaning towards the second problem. If the whole panel failed due to UV exposure, it usually starts to haze like a frosted car headlight first, and what I can see through it seems pretty clear. Polycarbonate does stress crack though. If the whole panel went brittle, then get the right wind conditions and it's going to shatter. But from stress cracks, you'll just get leaks where the crack extends past the washer, and the cracks don't tend to run far (so it isn't like the whole thing went brittle), because once the stress is relieved by the crack, it stops.

 

[Poe34]

Thank you for the responses. I might actually try to spray some FlexSeal on the perimeter of them and see if I can get a few more years before replacing them. It's too difficult for me to work up there for very long in an awkward position on a slippery, sloped surface! I went up with some GEOCEL 4500 but way too hard to work. I parked my front end loader under the skylight so I would slide into the bucket if I fell, lol.

 

[racecougar]

Won't FlexSeal™ just make replacement even more difficult/time-consuming?

 

[Bunsen Honeydew]

Just don't cover them with aluminum paint. A large factory near me did that. Later on, a roofer fell through one and died amongst the machinery on the shop floor.

 

[mikedodge]

Won't FlexSeal™ just make replacement even more difficult/time-consuming?

Thats what i was thinking. Like I said in my previous post I've made mine last a bit longer with Gorilla tape.

You can buy strips to put under them that match the ribs to give them more support. Most of my sky lights have been filled in with tin over the years.

 

[mopaarob]

Im considering these panels for an enclosed pool project...in Idaho. I looked into the extruded multiwall greenhouse panels but theyre pretty pricey. These will let in light but wont keep heat in. Any reason I couldnt make them "double pane" with rubber or foam strips separating them so theres air trapped between them to retain heat? I'd run the strips along the ribs and across each attachment point, mabe 1/8" thick?

 

[4xdog]

Polycarbonate has terrific — best in class — impact strength. That’s why it’s specified for some applications, like automotive headlight lenses.

But polycarbonate has pretty crappy weatherability. It’s crazed by moisture and degraded by UV. Coatings are a so-so solution — just look how fast headlamps weather.

Acrylic (PMMA, or polymethylmethacrylate, sold in the past as Lucite, Plexiglass, or Perspex) is a far, far superior choice for environmental exposure. Super low moisture pickup and exceptional UV resistance. It’s why acrylic is used for automotive taillights and outdoor signage.

If you end up replacing your panels, @Poe34, see if you can find something in acrylic.

 

[mikedodge]

Im considering these panels for an enclosed pool project...in Idaho. I looked into the extruded multiwall greenhouse panels but theyre pretty pricey. These will let in light but wont keep heat in. Any reason I couldnt make them "double pane" with rubber or foam strips separating them so theres air trapped between them to retain heat? I'd run the strips along the ribs and across each attachment point, mabe 1/8" thick?

That wouldn't do anything but also end up trapping condensation and probably not making them last as long.

 

[BombShelter]

You can plastic and solvent weld polycarb and acrylic, maybe try smearing some solvent around the area.

 

[sz0k30]

I have panels that run lengthwise on the peak on my 48' long pole barn. The barn was built over 30 years ago with the 1st set of panels. About 10 years ago had the barn reroofed and new panels installed to replace the 20 year old ones. Never any leaks or any cracks!

 

[tinmanwpk]

Two things come to mind. Perhaps the UV coating was damaged or defective. That's all that would make it brittle, and once it gets hazed and goes brittle, it's trash. But there is also one important installation note that if not followed can lead to early failure.

Polycarbonate thermally expands quite a bit. You're supposed to drill oversized holes and then drive the screws down to the point that the neoprene coated washer is in contact, but the rubber isn't very squeezed out. The polycarbonate should have the ability to move a bit under the washer. If it's trapped, that can lead to cracking.

We work with polycarbonate a lot. I totally agree with rlitman that you need oversized holes when you drill polycarbonate. And do not tighten screws too much as it will cause stress cracks and ultimate failure.

 

[Poe34]

Update to my original post. I called the supplier who the installers purchased the materials from and was told the skylights were still under warranty. They were just replaced today but I don't think the holes were drilled out and I think the same screws were used, I was not there. Fingers crossed they are installed correctly! I will take pictures in the next few days.

 

[geneg]

Update to my original post. I called the supplier who the installers purchased the materials from and was told the skylights were still under warranty. They were just replaced today but I don't think the holes were drilled out and I think the same screws were used, I was not there. Fingers crossed they are installed correctly! I will take pictures in the next few days.

If they used the same fasteners, insist that they replace them! The sealing washers & the flanges or washers are not suited for reuse. Seems like false economy or something worse. You will have leaks with a few thermo-cycles.

 

[Jetfixr320]

Brush pn flex seal will get you a couple years.
I think I would just replace with metal and be done with it.