Wall thickness for windows

Old 08-09-07, 04:05 AM
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Wall thickness for windows

CAn someone please tell me how I can determine my wall thickness for my replacement windows?? All of my windows are still in and I do not know exactly how to find out the actual thickness of the wall without taking the window out.
Old 08-09-07, 07:30 AM
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Open the window and remove the screen if needed. Measure from the backside of the outside trim to the backside of the inside trim. Backside being the side against the window and the side you do not see. This will give you the wall thickness including the siding and interior covering. This is best done at the side of the window as the bottom and top could be larger due to flashing.
Old 08-09-07, 09:25 AM
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You must not be doing a retrofit inside the existing opening, or there would not be a question. All replacement windows are 3 1/4" wide and sit between the blind stop and interior stop when performing a retrofit installation. Since the existing frame and trim stay put, the wall thickness would not be an issue.

But if you are completely removing the existing window frame and are installing new windows that have nailing fins, (a new construction type replacement) then I could understand why you have a question about the wall thickness, because you'd need to know how wide the extension jambs will need to be.

So if the 2nd method is true, and you are going to eventually be removing the entire window and trim anyway, just remove one piece of casing and stick a tri-square or ruler into the rough opening. You will feel it hit the backside of the exterior trim (that badeyeben mentioned measuring to) and you will be able to measure the exact wall thickness. Sometimes it's easier and more accurate to do it this way.

Assuming 1/2" sheathing and drywall were used, 2x4 walls are usually 4 9/16, while 2x6 walls are usually 6 9/16- but this varies depending on the thickness of sheathing and drywall. Sometimes the sheathing will be 3/4 or 7/8. Plaster and lathe also would make a wall wider than what is usual.

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