I am looking to change my double hung attic windows but have noticed that they are non standard size. Both windows fit in a rough opening that is 23.5" x 35.5". An old faded sticker on the window itself confirms a non standard window size of 23.125" x 35.125"

From my research, I've noticed that the closest standard size to my window requires a rough opening of 24" x 36". Looking harder, I did find a unicorn window that can fit a rough opening of 23.75" x 35.75"

However, absolutely no window that can fit my existing rough opening of 23.5" x 35.5".

Since I only need to take out 1/4" from all 4 sides of the frame to make the standard size of 24" x 36" RO fit, instead of re-framing the opening, I am thinking of taking a circular saw to the frame to establish the initial straight lines of the new opening and then carefully going for the full depth cut of the frame with an oscillating multi tool.

Does anyone see an issue with this approach?

 

it will probably also fit a RO that's 23.5 x 35.5, it just won't have as much space around it. As long as it fits, you don't need to make the RO bigger.

 

Thanks for your input XSleeper. That window is a Pella sold by Lowe's. Perhaps I should just buy it and measure it as it arrives to see if it fits. worst case scenario, I could just drive to Lowe's and return it. I wish they had it in stock at the store.

 

From Lowe's website:ThermaStar by Pella Vinyl Replacement White Exterior Double Hung Window (Rough Opening: 23.75-in x 35.75-in; Actual: 23.5-in x 35.5-in)


Notice the "actual unit size".

 

Yea. I've been reading into window sizing today. My understanding is that the "actual size" is always smaller than the RO size specs of the window and is (perhaps) the actual visible size of the window once installed?

Is the "actual size" spec the absolute largest dimension of the window, frame and everything?

 

Yes. That's what actual size means.

 

Perfect! It will be a tight fit but a fit nonetheless!
Thanks for the clarification!

 

A tight fit will also require a square (rectangular) opening. Carefully check the level and plumb of that RO.

Bud

 

Thanks for the tip Bud.

It should not be a problem to shave off a few mm here and there if/as needed. Easier than the 1/4" on each side as I had previously anticipated...

 

Have a friend who had her handyman install all new windows and he didn't pay any attention to "square". Some were a 1/4" from closing on one side. She had to force them down and latch them to even get close. I avoided looking at them when visiting.

Bud