Okay, so the job I did sealing that first window last week isn’t holding up. I’ve noticed water continuing to leak through even with the butyl tape and weatherstripping in place. And today I noticed a number of other windows are leaking at least as badly, if not worse. So, before I attempt to tackle sealing those, I’m putting together a rough plan of attack to try to deal with this once and for all.

To start with, here’s the Bussy McBussface video where I first heard about using butyl tape to seal off the windows:

I recognize it’s entirely possible I didn’t use the right kind of tape, or apply it in the proper way, to prevent leaks. So, I’m going to rewatch the video and see what else I can learn.

However, it’s clear that the weather-stripping I used as a (literal) stop-gap didn’t help at all, so I’ll skip that next time.

The materials I’ve used so far on this window include:

• 3/4″ wide butyl tape, applied around the inside edge of the bus frame
• 1/4″ weatherstripping, applied around the contact edge of the window
• DAP AMP Kitchen & Bath sealant, applied on the outside seam where the window and frame meet

Again, it’s entirely possible, if not likely, that I just didn’t use ENOUGH of any of these materials, so I’ll think about that. Another issue is the likelihood that the black rubber strip that holds the glass into the aluminum frame is also failing, so that’s another seal I’ll need to address.

So, one thing I realize, is that I didn’t really place the butyl tape with water-tightness in mind. My bigger concern was making sure it had enough contact to adhere to the window and hold it in. So, I am thinking that the tape alone SHOULD be enough, if I do it right. I tried not to have the tape extending over the edge of the bus frame, because I thought if it got trimmed by the window pressing against it that would be a problem. But thinking about it now, I can see that making sure that gap is entirely filled with butyl tape is going to be the first best way to keeping water from getting through. Getting some thicker & wider butyl tape would make this easier for the rest of the windows.

Another idea would be to go back and simply use the same materials the original factory used when building the bus – 1/4″ weather stripping and automotive seam sealer (the black goo). I don’t know if this is the best idea, since that’s what’s already in the windows, and clearly they are leaking. So, probably best to switch to something else.

I do also still think that a bead of exterior caulk on the outside seam of the windows would have to help keep moisture out, and maybe still some weather stripping on the tops of the windows to help block the airgap. But yeah. Going to go back out on the next non-rainy day I have free with the intent to pull and reseal this window right. I’m really starting to feel like I need to get this part taken care of before I make any more progress on the subfloor.

OH! And I also noticed today that there is still a good deal of water still coming in through the forehead, specifically around the clearance lights up top. I’ve been putting off doing anything about this part of the bus because I’m planning to cut the whole forehead off when I build up the sleep loft, but i can see now it’s worth at least sealing these off really well for the time being. At least it doesn’t have to be pretty.