Standard window gap allowed for window size

I have customer window install and one of the windows is about one inch smaller than the existing window. Is this normal? Shall I have them to remake the window exact size? What's the standard gap allowed? Thanks! By Jimmy

We measure the window opening and then subtract 1/4 inch. I would do the right thing and order another window.

Skydawggy,
You subtract 1/4 inch. Do you mean subtract 1/4 inch each side or both sides in total? Thaks a lot!

Subtract 1/4 inch from the total. That leaves 1/8 inch on each side.

Thanks for your reply and concern on this matter. By the way, do you know the industrial standard for window gap allowed? I need this to defense myself with my window co.

Are you saying you are trying to defend yourself for a mis-measured window? Most pro's will agree with what I have told you. However, there are companies that use 1/4 inch on each side in order to accomodate additional insulation. I don't know of any reputable company that allows 1/2 inch on each measurement. The idea is to do a custom fit and install.

Got it. I appreciate it for all your helps.

Hi, what's the general gap on each side supposed to have for the Patio door since I have no idear about it? Thank you very much in advance for your time.

There is no standard gap for any retrofit installation. The gap allowed depends on several different things. One of the main reasons for more takeoff on a particular opening is "How square the opening is. You have to leave enough room to square the new window up. 1" is rather extreme but if the opening requires 1" takeoff to allow the new window to be square in the opening then you must allow for it. In 30 years I can think of maybe 2 or 3 times that I had to allow 1" to properly square the window. And one of those three times I allowed 1-1/2" But in such cases I pointed this out to the customer with a level on the opening and then the window so they could see for themselves. The windows in cases like that usually look crooked in the opening but in reality the window is straight but the opening is crooked. On single hung windows you have more room to fault the window being square to aide some to aesthetics so it doesn't look as crooked. But the customer still needs to be shown what you did and why because if the window was hung a little out of square to help the appearance but still looks crooked the first thing your customer will do is put a level on the window. And being that it is not level you will have a call back on the job. And you will have to take your level and show the opening and the window and explain why you did what you did. So I prefer to show them during the install. My goal is to have NO CALL BACKS! And I have very few. In fact I haven't had one in at least three years.

measure your rough opening and subtract 1/2 inch. personally, i dont feel subtracting only 1/4 inch is enough to allow for any variance in wall studs and the like. especially in a replacement situation. the company i work for uses a 1/2 inch difference. standard. 1/4 inch gap on all sides... that should allow for any installation situation.