Window Fitters Guide to Window Installation 
19                ©2022 AWDI, LLC Do not reproduce without permission
Using approved sealant, apply a continuous bead to
the underneath side of the nailing fin of the window
or door unit.  Press the window into the opening and
secure the unit.
Apply the top horizontal section of flashing last.  Cut
to the same 9 inch width, the header flashing over-
laps and is sealed against the outer edge of the top
nailing fin. The header flashing should extend beyond
the outer edge of the vertical jamb flashing(s).
Building paper underlayment is applied in a horizon-
tal fashion, starting with the lower portion of the
wall, and over-lapping the upper application by at
least 2 inches.  
Be sure that the bottom portion is slipped up and
under the bottom of the jamb flashing(s), and the sill
strip flashing. 
Capping: Wherever possible, cover and seal the
existing opening frame, and/or the cavity created
between the newly installed window and the building
veneer with properly installed capping materials.
Capped Installations should have the capping 
materials integrate or seal to the perimeter of the
newly installed window or door in an air and water-
tight manner. Capping should be installed in such a
manner to allow ventilation and moisture to escape
from under the
capping.
For non-capped
Installations, use
suitable sealing
materials and
procedures to
create a weather-
tight seal
between the
newly installed 
window 
mainframe, and
the opening into
which it is
installed.
Sealing: When
possible, apply a
color matched
sealant where
capping profiles
abut one anoth-
er, but do not
overlap.  
NEW CONSTRUCTION 
FIN APPLICATION
Exterior Molding
Weather  Sealed
Air Seal Using Sealant, 
Backer Rod, and 
Contractor's Tape
SEALING THE INTERIOR/EXTERIOR 
AGAINST AIR AND MOISTURE
Air Seal Using Sealant
and Contractor's Tape
Exterior Capping
Interior 
Caulk
Backer Rod
Contractor's Tape
Sealant
Insulation
Contractor's Tape
Sealant
Insulation
RETRO-FIT 
APPLICATION
WITH EXTERIOR 
CAPPING
For non-capped installations, sealant should be
applied between the exterior window frame and the
building face.  It is recommended that the sealant be
applied to the sheathing.  
For a brick veneer and a non-capped installation,
apply sealant between the window capping and the
brick. It is recommended to apply the sealant using
backer rod as previously discussed.
SAMPLE MANUAL

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