Replacement windows - acceptable top/bottom gaps?

7 years ago

I recently installed 1 of 2 Andersen replacement windows without installation flanges. The total space to divvy up between the window’s frame and rough opening is just under 5/8”. I’ve seen an array of advice as to what the total space/slack should be, as well as how that slack should be divvied up between the top and bottom.

The window depth subsumes the majority of the 2x4 rough opening’s depth, leaving approximately a 13/16” set back from the room side edge, so not very much at all for the purpose of installing a stool.

Given this, pros, how would you recommend divvying up the 5/8”...a) even split with 5/16” on upper and bottom, b) less gap on top or c) less gap on bottom? I personally opted for to shim the bottom/sill side 1/8” leaving just under 1/2” on top. I was able to fill the gap from the exterior with 1/2” backerod and caulk over without any issue, although it’s bothering me somewhat to have that size gap. The interior side will be covered with wood trim and/or wood reveal extension, although it’s a pretty decent space from the exterior given I installed j-channel around the rough opening in lieu of exterior brickmound or flat trim. I’m leaning on adjusting to split the difference but would sincerely like to hear advice from pros before I move on to the 2nd window this weekend. I sincerely want to ensure that the window installations are in sync with standard practice.

Side note/question: does OSI Quad Max hold up well to weather? Attempting to smooth/tool was the weirdest caulking experience that I’ve had thus far. I’ve opted to use the standard OSI window/door/siding caulk for window #2.

Note: I did not and will not shim the at the top of the windows in sync with Andersen’s installation directions.

Featured Answer

PRO

HomeSealed Exteriors, LLC

7 years ago

Lots of ways to skin this cat novice, but the gaps that you've described are not outside the norm. Shim the sill to level, set sides to ensure that the window is square. Sash reveals are your best friend to do so. Side to side you'd want the unit to be relatively centered, but keep in mind that most openings are racked at least slightly, so don't be alarmed if the gaps are uneven from top to bottom. Again, squareness is key. 1/2" Gap on top is fine, make sure that its adequately filled with foam. If there are considerations for the existing exterior finish where you want the gaps more even, then that would be the reason to jack the window up a little. You can add lathe or some other filler wood under the sill as needed to accomplish that.

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Comments (9)

NoviceDIYer
Original Author
7 years ago
So, I need to state that the gap isn’t huge...I’m just very particular and envisioned there being a thin boundary from the exterior although these windows are on my 4th floor.
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NoviceDIYer
Original Author
7 years ago
Thanks for the very prompt response!
PRO
Windows on Washington Ltd
7 years ago
Totally normal spacing.
NoviceDIYer
Original Author
7 years ago
Considered both of your assertions regarding spacing, got out of my own head, and left the #1 as is...followed suit for #2. My sincerest thanks to both of you for your prompt responses.

I hope the two of you will be around commenting in six and 12 months when I tackle the remaining six windows on the back of my house.

FYI...I’ll need to figure out drip caps and the proper way to replace 4x segmented windows inside my kitchen...2x 33” x 64” DH windows and 2x 11” x 33” picture windows...installed very closely to one another to almost appear joined from the exterior.

Issues with kitchen windows:
1. From exterior, one easily view what appears to be protruding, swollen, rotting, and/or molded (blackened) wood below the 2x transoms and above the 2x DH.
2. From inside kitchen, the cross or “t” separating the windows isn’t quite that. The horizontal line goes across down then proceeds across. I suppose that’s what you get from Ryan Homes.
Goal for kitchen windows:
1. Take transom windows out of the mix entirely provided there is obviously rotted wood that must be demoed;
2. Eliminate poor attempt at “t” all together;
3. Actually join 2x ~35” x ~ 80” DHs
Uncertainty:
1. Permissible to remove “t” without shoring up vertical support for loading on exterior wall?
2. Appropriate way to incorporate drip cap with j-channel...drip cap between window frame and j-channel?
3. Appropriate cuts to drip cap when also using j-channel?
No need to answer here as I will re-post a ahead of actual need date.
PRO
Windows on Washington Ltd
7 years ago
Sounds good. Be sure to post up pics. Easier to visualize and comment on.
NoviceDIYer
Original Author
7 years ago
Makes sense given it was very difficult to describe. Here’s condition right now. I’ll make sure to post updates once all 4x windows are removed and rotter wood removed.
Sammy
7 years ago
last modified: 7 years ago
Do you have photos of the opening taken after it was prepared (weatherproofed) but before the window was installed?
NoviceDIYer
Original Author
7 years ago
Only one of the first window and it was dark outside by the time I was ready to flash the rough opening. Doing j-channel in the wrong order without removing all siding is tough given insufficient space to nail flange in-place. The flashing overlaps onto the newly installed j-channel as instructed/recommended by Andersen’s instructions.

Note: Provided these windows are on my 4th floor, all work was completed from the interior with the exception of clapping the partially removed siding back in-place (I called someone else to do it, me and heights do not mix).