If unable to cut 
the frame, you 
can collapse the
window frame,
carefully as shown.
The old window
should be out with
minimum damage
to the opening.
How to Prepare
the New Opening
Clean any debris
from the opening,
including old
shims, wood
mounting materi-
als and mounting
screws.
Measure the Height to determine if the old sill is at its
proper height, or if the old window “floated above”.
The sill needs to be established at the proper dimen-
sion, and it needs to be flat and level the full width of
the underlying framing. 
Thinset, or similar, can be mixed and poured into the
space to create the proper sill width, level and create
the proper height dimension. 
If possible, a 
properly sized
wood framing
member or vinyl
lumber pre-formed
pvc board can be
inserted to create
the flat, level sill 
in its proper 
position. This will
eliminate practice
of removing flange
to get new window
into opening.
Using new “buck”
material, place
new mounting
bucks on the
jambs and header.
Butt them together
at the corners, and
caulk seal all
joints.
Cut and prepare a proper sill pan (if appropriate), or
install a pre-formed sill piece to effect proper drainage
and proper mounting of the new windowsill and a
back dam to direct all water to the outside.
How to Install the New Window
A new window must be installed on a mounting buck
with stainless steel fasteners at the appropriate code
required quantity, with the fasteners of sufficient
length to penetrate the rough opening frame (block or
wood frame).
Plumb, square and level the window in the opening,
being careful to keep it as centered as possible.
Stackable, plastic shims, should be placed under
each mounting hole.
Window Fitters Guide to Window Installation 
136               ©2022 AWDI, LLC Do not reproduce without permission
Step 3.
Pry out old
frame
and shims.
Minimize
damage
to stucco
Step 4.
Mount New
Buck 1/2” 
to 3/4”
thick to
allow 
new Single
Hung unit
into 
opening
without
removing
flange
SAMPLE MANUAL

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