SHOP PRODUCTS
Houzz Logo Print
brandiatl

Replacement windows - acceptable top/bottom gaps?

NoviceDIYer
4 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.

Comments (9)