Skylight and Dicor?

[turner66]

I had an odd thing happen today... Went to my RV (at storage lot) to do some prep for the Thanksgiving trip, and I had a puddle of water on my kitchen island countertop. Water was dripping from the skylight trim on the inside.

So up on the roof I go and intially couldn't find any obvious cracks. Upon closer inspection, it looked like there was a crack around the perimeter of the skylight at the point where the Dicor sealant overlapped the flange. Sure enough, upon pushing back the Dicor a little, it looks like the Dicor actually disolved the skylight clear plastic (or whatever it is). I checked the one over my shower, and it isn't like this. I'm going to order a new skylight, but as a temporary fix I cleaned the old Dicor and flange with acetone and laid on another bead of Dicor all the way around.

I don't recall seeing that these 2 materials are incompatible.
Anybody else ever see this?
Should I use something else?

[hooligan]

My Georgie Boy manual, under roof care: Old seals must be cleaned with mineral spirits applied on a rag to clean and reactivate the surface enabling the new lap sealant to adhere to the old. "Skylights (not Vents) require sealing with Sikaflex #221"

[tegu69]

I just went yesterday to a local rv repair company to check out my leaking skylight. I have a 2012 fw that I purchased "new" 3 months ago. One corner of the skylight was cracked, slightly under the sealant. Evidently one of the screws was tightened too much, causing the crack. We contacted the manufacturer and they are going to send another skylight, but will only pay for 1/2 hour labor. It seems that the sealant is a maintenance item and will require the most time. The repair company also suggested installing a metal frame under the skylight.

[handsome51]

Their are different model number Sikaflex caulking. What is the model number of the caulking to use on the skylight

[Duck]

handsome51 wrote:
What is the number of the Sikaflex sealant to use. I checked and their are different types of Sikaflex sealant.

When you purchase the tube of Sikaflex check the bottom of the tube for an expiration date. The tube that my dealer was going to sell me at past the expiration date.
Don

[handsome51]

What is the number of the Sikaflex sealant to use. I checked and their are different types of Sikaflex sealant.

[turner66]

Just as a followup, I've bought 2 new skylights and will be installing soon. In preparation, I talked to some installers. Recommendation is to use butyl rubber tape between skylight flange and roof,screws,Sikaflex to seal, and DO NOT use Dicor. Hope that helps somebody else in future...

[turner66]

Thanks everybody for the feedback.

[turner66]

John&Joey wrote:
I'm glad you posted this, so many times on this forum people say to use Dicor on the skylight.

Many skylight makers state not to do just that. On my last MH the skylight manufacturer recommended Sikaflex sealant as the approved sealant.

Thanks for that. I'm going to contact the skylight manufacturer and get a recommendation before i do the new install.

[turner66]

ktmrfs wrote:
...
BTW acetone will haze, crack and damage some plastics. It can happen instantly, or it can take weeks/months before it cracks. It will solvent weld some plastics, not real good, MEK makes a better solvent weld. But still Acetone is not a good solvent to use around plastic unless you know what kind of plastic it is and if acetone will damage it.

No worries. I knew the risk of acetone and plastics. It's a temporary fix until my new skylight gets here and I replace the whole thing. I needed to make sure things were clean and quickly sealed well. I caught this problem during a "gap" in the weather knowing that we had hard rains on the way again. In fact, it's pouring right now, so it had about 12 hrs to set up. I'm heading over now to check it again.

[John_Joey]

I'm glad you posted this, so many times on this forum people say to use Dicor on the skylight.

Many skylight makers state not to do just that. On my last MH the skylight manufacturer recommended Sikaflex sealant as the approved sealant.

[ktmrfs]

my outback had dicor on the skylights, no problems after 3 years. then I cracked the skylight by accidentally stepping on it. My Bad. used Dicor on the new skylight and haven't seen any problem so far.

Dicor has Naptha in it to soften the EPDM roof material and form a good bond. Naptha shouldn't be a problem with most plastics. What may have happened is that the skylight flange was screwed down to tight and stress cracked from thermal cycling starting at the screw holes. That's a big problem with the skylight plastic.

BTW acetone will haze, crack and damage some plastics. It can happen instantly, or it can take weeks/months before it cracks. It will solvent weld some plastics, not real good, MEK makes a better solvent weld. But still Acetone is not a good solvent to use around plastic unless you know what kind of plastic it is and if acetone will damage it.

[2oldman]

I finally fixed my leaky skylight by a generous coating of Heng's roof seal. Caulk didn't do it, Eternabond didn't either.

[robsouth]

I would clean it good and put eternabond tape around the skylight and be done with it likely forever. Google eternabond and the proper methods for application.

[busyguy]

Hi
I had a crack around the edge of my skylight a few years ago. I had Dicor all around the edge and then after I found the crack I used Eternabond all around on top of the Dicor and up to the part of the skylight where it started to rise. Has never leaked again.
Good luck and if the crack isn't very big you may seal it with eternabond and not need a new skylight.
Busyguy