Best sealant for under windows/vent

[kaylaenglish]

Hey there! We just took our 13' scamp out last weekend and got rained on. We keep her under a cover at home during inclement weather, so we weren't aware that she has some leakage around the front/rear windows, and seeping slowly under the vent.

Recommendations for sealant? First time fiberglass owner here

[Alex Adams]

Although I haven't used it myself, a lot of people here recommend Dicor Sealant. There are two types, one is self-leveling for horizontal surfaces and the other is for vertical surfaces. Do not use Silicone based sealants! That's a no-no for Fiberglass.

[David B.]

Butyl tape is very good. It doesn't harden which makes removing the window or vent in the future a breeze.
Dave and Paula

[Casita Greg]

+1 For the double sided Butyl tape.
And it is what is used for most "factory installations." But to do it right, it will require removing the windows, (by unscrewing the inside window surround frame and gently pushing them outward to release,) then cleaning the mating surfaces of the window frame itself and the trailer hull around the rough opening to remove any old adhesive residue, and applying the Butyl tape to the window frame, (not to the trailer) before reinserting the window package. Obviously a two person job. After retightening the inside screws of the window, any excess Butyl tape that gets squeezed out by compression can be trimmed with a razor blade.
In any event, just attempting do a "quick and dirty cheap fix" by running a bead of caulking sealant around the perimeter will not last long. Do it right if you're going to do it at all, or else you'll just be revisiting the same problem a few moths down the road.

[Rzrbrn]

ProFlex, 3M 4200 or 4000, and Sika are good sealants. These harden slightly and do not attract dirt. Stay away from Amazing Goop and Parabond if used where they will be seen. At least I don’t recall 3M attracting dirt.

To use Butyl tape you have to take the window off. If you don’t want to do that use one of the above.

[Casita Greg]

Originally Posted by Rzrbrn

ProFlex, 3M 4200 or 4000, and Sika are good sealants. These harden slightly and do not attract dirt. Stay away from Amazing Goop and Parabond if used where they will be seen. At least I don’t recall 3M attracting dirt.

To use Butyl tape you have to take the window off. If you don’t want to do that use one of the above.

If you never plan to ever have to remove the windows again, ever, then the 3M 4200 and Sika Flex might work, but it would not be my sealant of choice for window packages. You'll bust the windows if you ever had to remove it later for some reason. I use both of those sealants regularly for many uses, and find them to be excellent, but they're not well suited for sealing a window frame. I'd stick to the Butyl tape, which is btw, what just about all the manufacturers use to bed their windows. Butyl tape seals quite well, and will allow the window to be removed later without causing damage to it.

And as to thinking that just running a bead of sealant around the edge of the frame as a "quick fix" will work, well, it may work for a short while, but it won't work for a long while. You'd be better off to just pull the windows and do it right. You'll be glad you did later down the road. Just sayin'.

[Rzrbrn]

A bit of work to remove the sealants I mentioned, but not really that difficult.

I have used ProFlex,3M 4000 (best UV resistance) and 3M 4200. I have removed all these a number of times, for one reason or another. To remove scrape with a plastic scraper, or being very careful, a wood chisel (which is what I have successfully done, much faster), then scotch pad, then Acetone for final clean up. If all else fails, West Marine Anti-Bond 2015.

For ProFlex, scrape as above, then final removal with scotch pads. Wash thoroughly after removal with Acetone.

My windows are sealed with butyl tape, then a bead of one of the above.

I have tried numerous other cleaning agents to do the final cleaning of the above but Acetone, mineral spirits, and alcohol seem to be the best. Dawn, Permatex 25122 Fast Orange, GoJo, mineral oil, and WD-40, and white vinegar sometimes work on unknown sealants as does MEK, toluene, xylene. I just keep trying different things until something works. I am well stocked.

I have never replaced a window. I just use the above. Works well for me.

[Larry C Hanson]

Old Thread

You might check this old thread....

https://www.fiberglassrv.com/forums/...ium-91001.html

Uncle Larry

[jspringator]

3M 4000. Use blue masking tape to keep a nice clean edge. I use lacquer thinner to prep services.

[Donna D.]

Please don't blob stuff over the window frame and the body. It will eventually fail and the you'll have a horrible mess to clean up. Do it right, pull the windows and rebed with Butyl. Done right, it will give you decades of leak-free use.

[wodowns]

I had a window leak, with water dripping from under its interior frame. Removed the window, resealed with butyl and that was no help. In desperation I placed a bead around the exterior frame with Lexel and still no help. Turns out water was entering rivets on the roof that were loose. After I replaced them with stainless bolts the interior is desert dry.
Water must have been running under the fiberglass exterior and finding the window frame. Might not be your problem but check it out.