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Window installation with wood siding - how to seal?

dmbaty's Avatar

Join Date: Jun 2013
Posts: 2

06-09-13, 09:02 PM   #1  
Window installation with wood siding - how to seal?

I've got an interesting situation. I'm installing windows in a what was a screened in room. I've torn out the old screens and wood trim.

The walls are constructed of (from outside in) WP-4 siding, 1in foam insulation, 2x4, WP-4 siding. The trim on the inside and outside is 1x2 or 1x4 on top of the WP-4. This all adds up to about 6in (without the trim). There is no moisture barrier. Pictures are attached.

I have ordered windows without nailing fins - Andersen 100 series windows. I've read through countless installation instructions, and I think I am close to the best solution. My current plan is to cover the entire window perimeter in butyl tape, overlapping the inside and outside by an inch or so. Then I would install the windows, caulk the outside and foam insulate/trim the inside. This seems like the best way to maintain some level of water tight seal around the window and the siding.

Does this make sense? I have another window that has been replaced and I am not quite sure how it was installed and sealed. I've attached a picture of this to give an idea of how the rest of the trim on the house looks.

Any suggestions/advice/comments would be appreciated.

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XSleeper's Avatar
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06-10-13, 04:45 AM   #2  
Why in the world would you NOT want a nailing fin? The window in picture one surely has one.

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06-10-13, 05:34 AM   #3  
I agree with X.
Your weakest point where waters going to get in with a flat jamb window will be around that trim to jamb seam.
Your going to be counting on just caulking to keep water out, which never works.
I would also have ordered nailing fins and used window tape to flash the bottom area before the window went in and on the two sides and top of the nailing fin.
How To Install New Construction Windows (In an existing home)

dmbaty's Avatar

Join Date: Jun 2013
Posts: 2

06-10-13, 08:54 PM   #4  
I had a few concerns with a nailing fin (which I am now questioning):

1. If I install it on top of the siding, I will be able to seal it, but won't be able to easily anchor it the framing. The 1in foam causes some issues here - the screws would hit the edge of the 2x4s.
2. Since I don't have plywood under the siding, I don't think I can cut the siding back and then install it that way. I would have to go back to the framing and then I would have an issue with sealing and trimming on the outside (1.5in from framing to siding surface without trim).

Does that make sense at all? Given the fact that I will soon have windows without a nailing fin, what is the best way to proceed?

Thanks for the help.

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