Window Fitters Guide to Window Installation 
128                ©2022 AWDI, LLC Do not reproduce without permission
Alternate 1:
If a precast concrete 
sill is used, coat the 
corners with liquid
flashing or seal the 
corners  to complete
the sill pan effect.
PreCast
Shaped Sill
provides back
dam and slope
for sill pan
drainage
Step 5:
If not using a prefabri-
cated sill pan, cut an
approximate 1x1 to
serve as back dam for
sill drainage and install
on sill buck.
Step 6:
Using liquid membrane
flashing material, coat
the sill, the back dam
and the jamb buck and
CMU up the sides 9”
and out on the face of
the CMU, inside and
out, 9 to 12 inches.
This will form a flashed
sill pan for proper
drainage of the cavity.
Step 7:
Apply bedding sealant
to face of buck on all
exterior surfaces to pro-
tect it from possible
water absorption from
the stucco material that
it will contact.
On the sill, leave 2”
opening in bead of
sealant in two places 
to allow drainage.
Cast Sill 
w/ Taper is
tough to seal
Buck
without
sill pan is
not 
sufficient
Exterior
Exterior
Exterior
Exterior
Coastal CMU Installation with Installed Buck
SAMPLE MANUAL

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