"DerbyDad03" wrote
"EXT" wrote:

Are you using "replacement" windows that sit inside the old frame, if it
is
still solid, or are you using "new construction" windows that sit within
the
house frame?

Derby, this is *key*. EXT knows much more than I do. So, if anything
conflicts, go with his (grin, presume he just like most presume I am a 'he')

The issue is that I keep hearing that what you see when you look at an
existing casement window - one that is not a replacement window - you
might not be seeing the actual rough opening. Part of the visible trim
and/or opening might actually be part of the window itself. On the
other hand, it might be as simple as measuring just like you would for
a double hung - side to side and up and down, in three different
locations.

What I'm specifically asking about is how do you tell the difference
between a simple "side to side/up and down" measurement of the exposed
opening and the more complicated "the whole frame is part of the
window" measurement.

Is there some way to tell by looking at the existing casement?

Not as far as I know. BTW, I am not sure why 'replacement window' vs
existing casement window is an issue here because to me, they are the same
thing when it comes to this. Kinda self trained. Used to working long ago
on anything from 150 years old, to 20 years old. Bugged the guys at the
various local hardware places for knowledge which they freely gave once they
realized I was serious. (Back then, 'women' and especially child females
didnt do stuff like that).