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Installing replacement windows in rough openings

I am in the process of renovating my old house on a budget. I obtained some vinyl replacement windows and am trying to install them into rough openings. My question is this, since these windows do not have any flanges to seal around the perimeter, is there anyting I can do, other that caulking, to prevent water getting in around the bottom of the window? There is a small gap between the frame and the opening.

Re: Installing replacement windows in rough openings

There's no flange on a solid wood window's sill either, and they've been installing them for hundreds of years. (I'm going to assume that you are installing some kind of sill under the windows which projects past the siding.)

Be sure to install a flashing on the bottom of the R.O. prior to installing the windows. There's been some excellent hi-tech flashings developed in the past several years, similar to ice & water shield for roofs. Anyplace that sells windows should also sell flashing material (lumberyards, home centers, etc). Then install siding or trim around the windows, caulk, & don't worry about it.

Re: Installing replacement windows in rough openings

Another recommendation would be to use spray foam in the cavaties around the window frame to seal air infiltration and to insulate but don't consider this as a water seal. This does an excellent job in filling all the irregularities in that space. This type of spray foam is readily available in a can anywhere.

Just be careful which type is used as they are available in different expansion rates. The low expansion one is preferrable but the high expansion ones work as well you just have to know how much to apply. The high expansion ones will expand 5+ times the volume applied. The trick with the high expansion ones is if it looks like there isn't enough ... it's enough.

If you're unsure which one you have a tip is do a test blob and see how much it expands this will give you an idea of how much to use.
If too much is used in the voids it can actually distort the window frame and prevent them from opening if they are that type.

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