what kind of butyl tape for this application?

[csarm]

I'm looking for the right material for re-doing the butyl tape on my window(s). In my research I've seen mentions of different types and sizes, specifically 3/4" and 1" and also: butyl tape, butyl putty, butyl tape in a tube, and butyl flashing (see pics). My window frames appear to be about 1.5" thick.
What is a good type and size of butyl tape for my application?

 

[Rene T]

Go with the tape on a roll. When it’s time to install it just unroll it and stick on either the window flange or the RV siding . Measure the width of the flange where the tape will sit and get that size. You could also maybe go with a size a little smaller than the flange. The tape will ooze out a little when you start tightening down. Make when you start tightening you do it in small increments and go from one side to the other side (criss cross) just like tightening lug nuts. When tightening like I said do just a little at a time. When it feels like the flange may be warping between the screws STOP. Let it sit for a few days then go back and tighten a little more. Keep a close eye on the warping. Then with a razor knife, just trim off the excess.

 

[Gary RV_Wizard]

Agree with Rene - the tape on a roll is easiest for a one-time amateur job. It's simple to handle and you get a continuous seal (but make sure the corners meet up). I buy mine in the mobile home section of our hardware store. Width isn't critical - the wider the tape the more squeezes out when the frame is clamped down. If you prefer to work with a caulking gun, butyl sealant in a tube is ok too. RV glass shops mostly use the guns, probably because it is fast and convenient when you do dozens of windows daily.

 

[csarm]

@Gary RV_Wizard and @Rene T, thank you! I'm now just trying to figure out which width- I'll go with butyl tape. It seems like 3/4" is more available than 1", but in research online, I'm finding some people are using the 1". Gary, I know you said that the thicker it is, the more it oozes, but I'm wondering if 3/4" would be sufficient? Are different window frames different dimensions? Would either of you recommend one size over the other for my application?

 

[Rene T]

How wide is the window flange?

 

[csarm]

@Rene T and @Gary RV_Wizard I actually tried it on one window with the 3/4" tape because that's all I could find right now. I ran into a few hiccups but it worked out and looks like a good seal. The next question is how to remove the excess butyl tape that oozed out around the window. I scraped away the big clumps, but there are still sticky bits and it looks pretty ugly (see pics). I've done some research on this but haven't found any great solutions. I tried mineral spirits but that didn't work so well. Any recommendations?

 

[Rene T]

Did it ooze out all the way around? It looks like it did in your picture. It should have to make sure you have a good seal. Also keep in mine, I would let it sit for a for a few days with the sun beating on it and then go back then see if any screws loosened. If they did just snug them up again. You don’t want to squeeze out all the caulking by over tightening the screws. No sense to do a initial clean up if it may ooze out more. Don’t warp the flange.
I would just use a razor knife and carefully cut down through the caulking just to a point the tip is just touches the siding. Then try a putty knife to remove the excess. If you’re still concerned about scratching the siding then get some plastic razor blades to remove the excess

 

[Gary RV_Wizard]

A plastic putty knife or blade works well, but careful use of a metal putty knife is ok as well. Most home or hardware stores have plastic knives and blades, so do Harbor Freight,Amazon & Ebay. Just peel away the excess, then use mineral spirits to wipe off any residue film. Run a thin bead of clear sealer around the top and sides (not the bottom) to finish it off. This is one of the few places where silicone sealant is ok to use on an RV, but Lexel, Geocel Proflex or similar exterior-grade clear sealants work just as well.

 

[csarm]

@Gary RV_Wizard and @Rene T, wow the plastic razor blades are amazing, thanks! I've never heard of these but got some per your recommendation and they work so well. Also, was wondering why not to apply sealer to the bottom of the window? Should I apply anything or just leave the butyl tape bare at the bottom?

 

[Rene T]

The thought is that if water gets trapped in the bottom of the window, there’s a chance it will drain out so you don’t want to seal it with silicon. Leave the tape the way it is right now.

 

[csarm]

@Gary RV_Wizard and @Rene T, I recently ran into a person who reseals windows using two other methods that I haven't heard of before and was wondering your thoughts.
Method 1) They remove the windows and clean them all up, but instead of replacing the butyl tape, they use a bead of silicone as the seal itself. Then they replace window and also use silicone around the window.
Method 2) Instead of removing the windows, they carve out a valley (about 1/2" deep or so) in the old butyl tape/putty that's currently there, between the window and the wall. Then, they apply a bead of silicone in the valley.
I likely won't be able to redo all the windows before monsoon season hits, so I'll do some and someone may come over and help me with some of them. The person who would come uses the above methods, and I'm curious as to whether either of the methods are any good?

 

[Gary RV_Wizard]

Some professional RV glass shops like to use a caulking gun to apply the sealer - it's faster for them. I probably wouldn't use pure silicone, but an acrylic-silicone blend (as is used on house window frames) should work. However, it is a semi-permanent seal and harder to remove if you need more window work in the future. You can also get butyl caulk in a tube - it is widely used on metal gutters and flashing - but most amateurs find the tape simple and effective.

Method 2) Instead of removing the windows, they carve out a valley (about 1/2" deep or so) in the old butyl tape/putty that's currently there, between the window and the wall. Then, they apply a bead of silicone in the valley.

I don't understand the second method - how do they get sealer between the window frame and sidewall without removing the window? And how to make a 1/2" valley in a layer that is probably only 1/16" after being squeezed? But that's not important - it's still a silicone sealer instead of butyl tape. Same drawback in the future.