I'm replacing a window with a Jeld Wen Better Series window that’s 2-29/32” deep. The window frame is the standard 3-1/4” deep. I’m dry fitting the window and there’s about a 1/4”gap all the way around the window between the window moulding and the window itself (due to the window not being as deep as the window frame). Has anybody ran into this issue? Will this require all of the moulding to be redone? My issue is I’m struggling to find window stop moulding with the correct width now to fill the gap. Any recommendations to make this work or am I better off ordering a new window that’s 3-1/4” deep?

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    Welcome- It would be great to include pictures of what you are talking about- Is it a wood window jamb with interior and exterior wood trim ? Stucco, Brick, Concrete ? I am not sure what you refer to when you say window frame. Does the window have a nailing flange or is it a block frame window (no flange). What are we looking at for the hole the window is to go into ? Please give us a better idea of your issue.
    – Kyle
    Commented Aug 22, 2022 at 5:14
  • @FreeMan that's apparently the problem, and the correct solution. Post an answer.
    – isherwood
    Commented Aug 22, 2022 at 13:02

2 Answers 2


Our house is old enough that it was framed with true 2x4" studs, but our slide-in replacement windows have a jamb thickness for modern 2x4s so they're actually 3.5" thick. Knowing this, the windows were custom built with jamb extension to make up for the extra 1/2".

It sounds like that's what you'll need to do with yours - make a jamb extension that is 11/32" wide to bring the window jamb flush with the interior wall.

We did the same thing with a standard off-the-shelf interior door when we did a minor interior remodel many years ago. Since we didn't want the jamb extension to be visible as a line in the jamb, we also resawed a 2x4" into a "veneer" layer about 1/8" thick and attached this all the way around the jamb (top & both sides, you'd need to do the bottom, too) in order to hide the extension. We then finished the "veneer" to match the rest of the door casing. You could do the same if you wanted to hide the extension. You could also buy a piece of 1/8" plywood and cut pieces from that, as well, if you don't have a table saw or bandsaw to resaw the 2x4".

  • OK, that makes sense. Thanks for your help!
    – Tmac
    Commented Aug 22, 2022 at 13:36

There are 2 things you ought to do - one, you will likely need to replace the moulding, but you will also want to insulate it. You can either push fiberglass insulation into the gap or use NON-EXPANDING foam. Make sure it is NON-EXPANDING or it will push against your window and cause it to negatively effect your window operation.

For the moulding, there are typically versions that are slightly wider that you can use, but you're probably not going to be able to reuse the existing.

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