Why seal AND tape window flanges?
matt2491
| Posted in General Questions on
I’m curious why I see so many people run a bead of sealant around a new window opening, install the window, and then tape over the flanges anyway. Is this not accomplishing the same thing? Just a belt-and-suspenders thing?
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Replies
I have to agree with you there. I will say that install instructions on Anderson at least say to do both. On my own windows I only tape them. Plus you're also spray foaming around the window after that.
Haven't had to take out a window and try to save it when it's been caulked in there too. Good luck!
The reason 99.99% of window warranty leak claims are denied is because almost no one ever reads the install instructions and only 1 percent follow them.
Walta
Interestingly, according to this article by Joe Lstiburek, "sealant is not necessary (or desirable) behind the window flanges."
https://buildingscience.com/documents/insights/bsi-085-windows-can-be-a-pain
matt,
I did it on a few windows in one house and stopped. By the time the window was shimmed and moved around in the opening to be centered, that neat bead of sealant they show in AI generated installation videos was gone.
Another vote for it being silly and really just an opportunity to create a mess.
In the article Matt linked Lstiburek doesn't show it. But I do think it's advisable for the tape to overlap not just the flange but also to include the frame, so that the joint at the flange and frame is covered by tape. Unless the flange and frame are from a single, molded piece of pvc there is a joint here which can be troublesome.
jollygreenshortguy,
I agree with you. I seem to recall occasionally seeing that called out in manufacturer's instructions, but not often. I always used to run a bead of Lexel or something up the joint between flange and frame as CYA. I don't have any evidence to back this up, but it seemed like a good idea and cheap insurance.
Paul,
I don't know where we stand with manufacturer's instructions. Do those include the installation videos they post on Youtube which often contradict the ones on their website?
When I discussed the subject with my lawyer he said that breaches of the instructions would not void the warranty if they were not materially connected with the defect in the product that caused the problem.
Hah, great point Malcolm - I usually assume that the manufacturer wants you to follow the instructions unless the instructions are wrong, which as you point out they often are, and that I'll be battling them if a warranty issue comes up regardless. Sort of like trying to get a warranty claim on asphalt shingles (well..... maybe not quite that futile).