Skylight issue

[alexl]

Hello all,
I recently replaced the skylight on my travel trailer, it went on great but a week later, the edge is all wavy as pictured. This was a brand new pvc roof and brand new 14x22 skylight. I used high quality butyl tape between the membrane and the skylight flange and alpha system lap sealant on top. Any idea what happened here? I took it back off, cleaned off the sealant, but there is memory to the skylight, looks like I (frustratingly) have to toss this new skylight and try again. Just don’t want the same result..

 

[CharlesinGA]

How wide is the flat flange where the screws are? an inch? Honestly, I think I would head to the metal rack at Home Depot and get some inch wide flat aluminum, an eighth of an inch or so thick, and cut the pieces and drill them up to match and lay them on top of the skylight flange and screw it down. WARNING.... RANT COMING..... I always get pee owed when I see sealant put on like that without any masking tape used. Most say, "its the roof, you cannot see it" but my OCD as a 31 year airline mechanic (and we did a lot of sealant) tells me it needs masking tape, pull it off as soon as the sealant begins to skin over. Timing is everything. Here is what I am referring to...........



No its not perfect, but pretty much a straight line, edges are sealed, no blobs and gobs of sealant everywhere it should not be. (this was my first, and only roof)

Rant off..........

Make sure your holes, In the dome, but not in the aluminum, are drilled oversize so the Lexan can walk around and not be restricted by the screws, and I'll bet it stays flat. Also, work from the middle of each side to the corners and don't tighten them crazy tight the first time around. Let it sit for an hour or so and snug them again, letting the excess butyl ooze out. Use a plastic or wood scraper to remove all excess butyl before sealing. I used Dicor self leveling on the roof of the trailer, and Dicor "no run" sealant along areas where the self leveling could not be used. For small beads along edges of clearance lights and similar stuff, I prefer Geocell, but the Dicor products were excellent for the roof job.

Charles

 

[Contributor]

I wouldn't worry about the wavy on the outer edge, I would just add some more dicor until it sealed. I hate to remove any screws on my RV and reuse the same spot as there is nothing for the threads to bite and eventually it just loosens.

 

[Rene T]

Welcome to the forum.
What is alpha system lap sealant? Is it compatible with the skylight material?

 

[alexl]

I wouldn't worry about the wavy on the outer edge, I would just add some more dicor until it sealed. I hate to remove any screws on my RV and reuse the same spot as there is nothing for the threads to bite and eventually it just loosens.

That’s probably what I should have done. Just don’t trust lap sealant as the primary seal.

Welcome to the forum.
What is alpha system lap sealant? Is it compatible with the skylight material?

Basically the same stuff as dicor, just made by LCI for their tpo and pvc membranes.

 

[Ray-IN]

Screws too tight caused the Lexan to bow. Now it is set, no other options but to use more sealant or buy new skylight and begin again. I doubt removing it, heating with a hair dryer and flattening will work, but might be worth the time and effort.

 

[Rene T]

Screws too tight caused the Lexan to bow. Now it is set, no other options but to use more sealant or buy new skylight and begin again. I doubt removing it, heating with a hair dryer and flattening will work, but might be worth the time and effort.

I would remove it and set it on something flat. Then like you said using heat, apply it to the flange then put something real heavy to flatten it. Do each side one at a time.
When installing it, I would drill another set of holes between the existing ones then using stainless steel screws tighten then ever so slowly and just enough so that the butyl just starts to ooze out. Let it set for a few days in the sun then torque them again. Then apply the Dicor or similar

 

[Contributor]

Perfect is the enemy of good enough.

Removing, cleaning, applying heat, flattening it, drilling new holes, re-installing and re-sealing is a problem waiting to happen.

Drilling new holes in the skylights are tricky as the drilling will cause cracks on the edges. Been there, done that.

If you do go ahead and redo it all, please do us a favor and report back.

 

[SpencerPJ]

An extremely thin skylight, a less than steller job cleaning the old caulking off, and over tightened screws. But still, I would simply wait a week, and another tube of Dicor to it.

 

[Ex-Calif]

Screws too tight caused the Lexan to bow. Now it is set, no other options but to use more sealant or buy new skylight and begin again. I doubt removing it, heating with a hair dryer and flattening will work, but might be worth the time and effort.

Yup - There is a tendency to overtighten "glued" joints. The fasteners need to be brought down even until the butyl tape starts to squeeze or the sealant starts to squeeze out.

Over torqued screws will continue to apply pressure and they will slowly relieve themselves by continuing to deform the lexan.

 

[Rene T]

Depending in how far apart the holes are, I would have no problem drilling extra holes

 

[Ex-Calif]

Depending in how far apart the holes are, I would have no problem drilling extra holes

Yes and there are low angle drill bits for drilling plexiglass so the bit doesn't snag and crack it.

(ex aviation mech - ask me how I know - expensive mistake...)

 

[Rene T]

Yes and there are low angle drill bits for drilling plexiglass so the bit doesn't snag and crack it.

(ex aviation mech - ask me how I know - expensive mistake...)

They may be made out of Lexan so there would be less chances of cracking

 

[Contributor]

I re-did mine earlier this year. Removed all old dicor, lifted up edges where there was dirt and crud working it's way in to the inner edge. Cleaned with a rag soaked in alcohol and putty knife and let it dry.

Mine (2004 Keystone Zepellin) did not have butyl tape as the sealant but it looked like regular dicor. I squeezed dicor into the areas between the roof and skylight. Some screws would not tighten so I had to drill new holes (5 or 6). I don't know if the skylight is made of Lexan or plexiglass, but a couple of them cracked no matter how careful I was. Lots of dicor and good for another year before I get up there again to inspect. Neat is not necessary in my book.