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Skylight/vent replaced - turned into a bigger job than expected...lol


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Well, I replaced the skylight earlier this week and it was actually a fairly straightforward job. I did uncover shoddy work by a previous person, but I don't blame it on the older couple I bought it from as the gentleman didn't like heights so no work was done directly by him. My inspector did identify it as a problem, but we just thought the tape and sealer was old needing replaced.

I decided to replace the skylight with a smoked version to cut down on light entering the coach since the existing lens was old. I scrapped off the tape and existing sealer to uncover the screws, and things seemed old compared to the videos I watched online. The old skylight was tough to pull off due to excessive butyl sealant. Once it was out of the way, I realized why the skylight looked odd on the roof. The sealer and tape looked separated, but that wasn't the main issue. The skylight had been replaced previously, but whoever did the work didn't remove the prior skylight. It appears they cut the dome off the original skylight, and then just dumped a bucket of sealant on the old lip and screwed the then new skylight on top. That's why there was a huge gap. It's unbelievable that someone would do that rather than do the job correctly.

I removed the gallon of sealant and old flange, and the frame underneath was quite nice. I cleaned it well, and then installed the new smoked skylight correctly. Once done, I used Dycor lap sealant but it's didn't flow as well as expected. It moved a little, .5 inch or so, but it really didn't level out like the video's showed. It's sealed fine but I just don't like the lumpiness of it.

I also replaced the vent on the roof since the cap was cracked at the top. It was an easy repair by comparison.

I cleaned off the roof where it was dirty, but I'll need to plan another trip up there to give it a good soap washing so it's more presentable. No one will see it, but I'll feel better knowing it's clean and nice.






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9 minutes ago, vito.a said:

Polycarbonate skylights require a special sealant or they will crack.  

You really need to remove all the Dicor.

The proper sealant is Surebond 140.  It does not contain petroleum distillates.  You can find it on Amazon.

I did use the correct ICON sealent for the skylight where it attaches to the roof after cleaning all the old off stuff. The dicor was only used on the outside lip which is what was recommended.

Never heard of the surround stuff or I didn't come across it when researching. Hmm...

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I quit having RV shops apply Dicor Lap Sealant after having my shower skylight and Fantastic Fan both resealed in Anchorage Alaska on one trip back in 2012.

The shop in Alaska called Karen's RV ONLY uses Sikaflex-715.


It lays flat with no lumps or bumps plus easy to keep clean and white.

Edited by Dr4Film
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On 12/5/2021 at 6:20 AM, OhReally said:

And oh, by the way, some skylights are doubled up with a small gap between them for thermal purposes. Are you sure you didn't remove the inside skylight?


No, it was the inner. It still had a bit of the curve on the outer edge and the lip around the outer roof left no question.

9 minutes ago, Bjohnsonmn said:

Where did you get your skylight from?

Ordered via Amazon from ICON 

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40 minutes ago, Bjohnsonmn said:

Thanks! When you sized it, did you measure the outside dimensions of the flange, or the bubble part.

I measured both the dome and outer flange just to verify the new one was the proper size all around.

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6 hours ago, Grampy OG said:

Mine is positively awful on '03 coach. Your clean job has inspired me. I'm with Brad, where did you get it and how did you measure?




Thanks for the compliment 

I bought the skylight from ICON, and I used their measurement table to determine which one to buy.

I checked this measurement:




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Search on iRV2.  Not having a metal flange applied over the polycarbonate or acrylic lenses is almost a sure prescription for future failure...EVEM with new plastic. The plastic simply DOES NOT have the strength to  distribute the force of each individual screw without distorting the plastic and failing to provide a secure, long-lasting seal.

If you want to do it only ONCE, reinforce the uppermost layer with metal so that the clamping force is evenly distributed over both the clear sections and whatever sealant you use.

Beware, as another poster advised, Dicor Self-leveling sealant will result in micro-cracks (leaks) in only a couple of years, IFF it touches the clear plastic.  Use only sealant rated for contact with polycarbonate (Lexan) or acrylic where it touches the clear plastic.

It ain't rocket science, but the clear plastic is not able to provide the strength necessary by itself, without some sort of reinforcement...witness the multiple failures reported on this forum and others.

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