Replacing window

Question

I am replacing a window in a garage. I measured the rough openings but the current window in the garage is quite old and I am not even sure what kind of window it is (or the proper terminology for this kind of window).

I want to put a 'normal' double hung replacement in the garage, but I am curious if there are any special precautions when replace a window of this type.

Here are some images of the window:

When I measure the rough opening I noticed that the window had a metal frame that a was a little bit wider than the rough opening, which made me think that perhaps this would cause some issue during replacement.

Pardon the appearance of the garage; it was not well maintained and I am trying to fix that.

Answer 1

It's a slider, as @bib says. No "special precautions" having to do with it being a slider when replacing - the precaution for any window opening (new or replacement) is accurate size/measurements, and careful attention to flashing to direct water correctly (the new window should have detailed instructions.) It's also normal and expected that the window does not, should not fit "snugly" in the opening - some space is always left to allow for shimming it precisely.

It's perfectly normal to have a "flange" on the window that is wider than the rough opening. It's a major part of attaching the window. Remove any exterior windowframe and look for fasteners.