The importance of proper measurement must also
take into account depth, because the depth of the
opening after removing the old window, will deter-
mine the order size of the window and the method 
of installation and requirements for finish trim inside
and out.
Standard 2 x 4 construction, with sheathing on the
exterior and wall board or sheetrock on the interior
has, for the most part, standardized measurements.
From the outside surface of the sheathing to interior
surface of the wall, the default dimension will be 
4 and 9/16 inches.
The residential window universe consists of three
basic window frame materials – pretty much 
distributed evenly when it comes to existing 
windows needing replacement: Wood frame, 
Metal frame (steel and aluminum), and Vinyl 
frame (similar with composites).
Window size is influenced by whether the old window
and its trim is removed down to the rough opening;
or if the window is removed and the old trim remains;
or if the old frame of the window remains and only
the operating and glass panels are removed. 
If the old window and trim is removed down to 
the rough opening, the replacement window will 
be as big as possible to fill the opening. This can 
be important because the bulkier frame material 
for modern replacement windows tend to reduce 
the glass area that is not always desirable to the 
consumer – especially for smaller windows.
If the trim remains, then the replacement window 
will need to fit to it, altering and probably increasing
the needed work to install the new window.
If the old frame is left intact the new window needs to
butt to it, fit inside it, or sit on top of the frame; again
influencing the cost and complexity of the installation
of the new window.
The illustrations show common existing conditions
for old windows to be replaced. The next illustrations
show the various openings after either partial or full
removal of the old window. 
Whatever method is chosen, proper installation is
possible remembering to accommodate the water,
moisture, air, thermal and vapor barriers. Best 
practices for all are covered in detail throughout 
this manual.
Frame Depth
Window Fitters Guide to Window Installation 
26                ©2022 AWDI, LLC Do not reproduce without permission
Metal Window
2 to 2-3/4”
Common
Frame Depth
Wood
Window
3-1/2”
Pocket
Wood
Window
4-9/16
Frame
Depth
Finned
Window
3-1/2” Overall
2 to 2-1/2”
Setback
Steel
Casement
Window
2 to 2-1’4”
Frame 
Depth
SAMPLE MANUAL

View this content as a flipbook by clicking here.