Window Fitters Guide to Window Installation 
42                ©2022 AWDI, LLC Do not reproduce without permission
Step 2:
Cut-back the siding
with circular saw or
Oscillating Tool 
sufficient width
(approximately 1/2”
to 2”) to expose the
old window’s 
mounting fin.
Take care not to cut
too deep.
Step 4:
Removed the nails
carefully from the old
window’s fin.
Nailing Fin Frame-Out- Alternate
Step 3:
Removed the siding
carefully nails carefully
from and make adjust-
ments as necessary to
expose the complete
fin.
Try to disrupt old
flashing as little as
possible.
Remove all the siding
pieces from around the
window as cleanly as
possible- trying to 
preserve any flashing.
The cleaner the 
cutaway, the easier
and better the finished
replacement will be. 
Step 1:
A very common window
installation of an old
finned window has the
mounting fin covered by
“J” Channels and drip
cap and has the 
siding butting up 
to the “J” Channel.
Re-flash the exposed 
mounting surface using 
adhesive-backed flashing or liquid 
flashing. Cut a new drip cap to tuck under 
the siding after the new window is installed. 
If a Fin-Mounted Window has the fin covered with J-Channel and siding, the siding can be cut back to expose the nailing fin making the old
window easy to remove. Once the new window is installed and flashed, exterior trim molding can be applied as shown on previous page.
SAMPLE MANUAL

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