Install new construction vinyl window on "wavy" wall.


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Old 03-31-15, 10:50 AM
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Install new construction vinyl window on "wavy" wall.

Hello,

Back in December, '14, I posted a topic "Need Advice on installing Pella Thermastar Slider". I fiddled with that window for more hours than I care to admit to trying to get it to open and close smoothly.
I have come to the conclusion that the wall it is installed in is (at least) contributing to the difficulties. The Andersen slider that the Pella is replacing never slid well either.

Last week, I decided to try to give the window a better surface to mount on, so I removed the window. Fortunately, I had used screws to install it.

Here's what I'm up against.
  • Right side of window is plumb
  • Bottom of window, sheathing is flat (i.e., straight edge does not rock or expose gaps).
  • Left side is out of plumb. The bottom would need to be shimmed out about 3/16" to be plumb (see pic)
  • Top (Head) is bowed. High spot is near center of window.
  • Top left side would need to be shimmed out about 1/8" to be flat (see pic top right).
  • Top right side would need to be shimmed out about 3/16" to be flat (see pic bottom right).
  • If I shim the bottom left to make the left side plumb, that would about double the amount the top left needs to be shimmed to correct the bow.
  • If I shim the top right, that would take the right side out of plumb.

This is feeling like I'm trying to true a badly warped bicycle wheel (and I never was very good at that!).

What material should I use to do any shimming? I want the material to be dimensionally stable.

What should I do to make that wall opening a better home for the vinyl window?

Thanks in advance.
 
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Old 03-31-15, 11:50 AM
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I use synthetic shims as they don't tend to split like the wood ones.

I have run into window openings like your's and I don't have a magic trick. I just shim, space and curse until I get the window attached level, plumb and square and operating smoothly. Then the fun part is figuring the best way to do the trim. Caulk can hide minor sins but at some point you start cutting the trim in pie or wedge shapes to make it work and conceal the errors as best possible.
 
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Old 03-31-15, 04:11 PM
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Windows don't necessarily need to be plumb like a hinged door does, so personally, I would not worry about plumb at all. The header might be bowed due to a bunch of pieces being used to sheath the opening rather than sheathing over it and cutting the opening out with a router or sawzall. I would probably use a prybar to open up a gap between the sheathing and the framing, and hammer a standard cedar shim up in each upper corner (maybe 1/8" per side, right and left) so that the sheathing is flat... or flatter. I would not shim the bottom if there is no bow. The opening may still be a little wacky right to left, but it will not probably cause you a bit of trouble. As long as the head and sill are flat and straight and no longer curved, it will operate just fine, provided you install it level and square.

In a perfect world, both sides would be in the exact same plane (although not necessarily plumb, they should match and be out of plumb the same amount.) In a perfect world, you would take 2 strings and cross them in the form of an X over the opening to determine which corner needs to come out, and how much. I highly doubt you need to go to that extent... all it will do is cause you big problems when you go to trim the window by creating tapered jambs on all 4 sides.

Also take into consideration that if your eye or level is the tiniest bit out of whack that you could keep going around and around in circles shimming that window and never get it perfect.
 
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Old 03-31-15, 06:46 PM
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Thanks @Pilot Dane and @xsleeper.
As you pointed out, the trim would certainly be a challenge if I went crazy with the shims.
xsleeper, you're right. I re-sheathed the wall and used separate pieces to butt against the old window. Initially, I was going to try to keep the old window so I pried up the flange and slid the plywood under it. But, as you can imagine, the flange didn't hold up against all that abuse and we just decided to replace the window.
I used screws to attach the sheathing, so I may be able to back off a bunch of screws around the corners of the header. Then I'll try to pry out those corners.
 
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Old 04-01-15, 05:15 AM
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You are correct about not needing plumb. The important thing is that it's all in one flat plane so you don't try to twist or bind the window.
 
 

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