What size to order given diagonal measurement difference?

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bulb120
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Joined: Wed Nov 12, 2014 7:43 pm

What size to order given diagonal measurement difference?

#1 Post by bulb120 » Wed Nov 12, 2014 9:48 pm

I'm replacing 21 original (early 1980s) wood windows (single hung, single pane) with vinyl pocket windows. Twenty will be double hung (11 32x54, 7 32x74, 2 24x62) and one is a picture window (48x62).

As far as I can tell all of the frames, sills, exterior stops, etc are in good shape. I'm planning to install by removing the existing interior stops, sashes, jamb liners, and springs and then inserting the vinyl window from the inside.

I made all the measurements as commonly recommended (horizontally from jamb to jamb in 3 places, vertically from top jamb to where the sill meets the stool in three places, and diagonally). I plan to size the windows 1/4" less than the smallest horizontal and 1/4"-3/8" less than the smallest vertical.

For each window, the 3 horizontal measurements and 3 vertical measurements were either always equal (or one was off by 1/16"), so I assume I'm good there. The diagonal measurements, however, were mixed. Most (17) of the windows have diagonals that differ by 1/4" or less (mostly less), which I've read is fine for the sizing i listed above. Is that correct?

Four of the windows have diagonals that were different by 3/8" - 7/16". I'm hoping that (1) this is because I'm measuring to the lower corner that has the jamb liner and the liner may be bent outward a little or that (2) I could remove the interior casing and square these up enough once the old windows are removed. (Note: all the existing windows raise and lower as well as to be expected from a 30yr old wood window). Given these possibilities, should I consider ordering slightly smaller windows for these openings (three are 32x54 and one is 24x62)?

Thanks for any advice and suggestions!

TheWindowNerd
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Re: What size to order given diagonal measurement difference?

#2 Post by TheWindowNerd » Thu Nov 13, 2014 7:06 am

The new windows need to be installed square. That does not mean level, though level is preferred.

I would use the existing sash reveal to tell me how much I should deduct for the install. Also you need to know the frame of the new window if it has any legs that can be cut off to adjust as needed.

bulb120
Posts: 6
Joined: Wed Nov 12, 2014 7:43 pm

Re: What size to order given diagonal measurement difference?

#3 Post by bulb120 » Thu Nov 13, 2014 9:06 am

What do you mean by "existing sash reveal?" My existing window frames look like what is shown in the diagram in the link below and I made the measurements as the diagram shows. (Only difference is my existing windows don't have a wooden vertical parting bead - the aluminum jamb liner has the parting bead in it.)

http://www.pedantique.com/wp-content/up ... indows.gif

TheWindowNerd
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Re: What size to order given diagonal measurement difference?

#4 Post by TheWindowNerd » Sat Nov 15, 2014 6:23 am

The sash reveal is the relationship between the lower sash rails, the lower of the lower sash and upper of the upper sash. to the window frame and or stool. This reveal should be the same at both ends of the rails.
Lets say one end of the lower sash shows 1/4' on the left and nothing on the right. The window is then out of square by 1/4", thus you need to allow more tolerance for the insert frame to be squared up when installed.

bulb120
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Joined: Wed Nov 12, 2014 7:43 pm

Re: What size to order given diagonal measurement difference?

#5 Post by bulb120 » Sun Nov 16, 2014 8:57 am

Ok, got it. My old wood windows are single hung, so the top of the top sash is hidden by the top exterior stop and top parting bead. The bottom sash has enough play in it that I can't tell the squareness of the frame from it. Given this scenario, how then would you judge the "squareness" of the frame and whether or not you need to take more than 1/4" off the height and width to size the replacement?

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