Window Fitters Guide to Window Installation 
5                ©2022 AWDI, LLC Do not reproduce without permission
Application: The new window must be installed
plumb, level, and square. Make sure loads from the
wall above are not transferred to the window.
Shimming:  All shimming should be done with the
proper pressure to the mainframe of the newly
installed window to guarantee the proper operation
of the window sashes.
The shims should be made of a material that is
hard enough to support the window, provide good
thermal insulation, resist decay, and allow for 
fastening to run through.
Fastening: To fasten the window properly to 
the opening, use corrosion resistant fasteners of 
sufficient size and length to permanently anchor 
the new window.  In most cases, these anchors 
are supplied with the window unit.
1. Fastening for Replacement or Renovation:
Fasten to the jambs, and/or head sections of the 
left-in-place frame using corrosion resistant screws,
or nails when conditions permit.  Use non-tapered
shims as needed, and install at all fastening points. 
2. Fastening for New Construction: Fasten the
“new construction” vinyl window into the opening
structure by fastening the integral fin.  Take care 
to allow for natural expansion and contraction of 
the window or door fin. Use cap-nails along header 
as shown elsewhere. Shim any gap present between
the new window and the opening, as needed. Use
corrosion resistant fasteners. 
Caulking:  
1.  Replacement: Use caulking during mounting
of replacement vinyl windows as follows:
Inside/Out Application- Apply caulk to the 
back of the exterior stop, and under the sill when 
the newly installed window is mounted against the
exterior stop leaving weep gaps.
Outside/In Application- Apply caulk to the 
back of the interior stop, and under the sill when 
the newly installed window is mounted against the 
interior stop.
2. Renovation & New Construction: Caulking
alone is not recommended for use during renovation
or remodeling installation. Instead, use proper 
flashing methods described in detail elsewhere.
Insulation: After new vinyl window is mounted in
the opening, inject PU foam between the window and
the rough opening (RO) to insulate any perimeter
voids between the mainframe of the new window, and
the opening. 
Do not compress the insulation to avoid pressure 
on the frame of the new window that will distort 
the frame, which could  impede smooth operation 
of the new window.  It is also recommended that a
proper air seal on the warm side of the insulation 
be provided.
Interior Air/Moisture Seal: It is recommended 
that an air and moisture seal be provided on the 
interior side of the rough opening gap using sealant,
or Barrier Tape.  To prevent drafts, heat loss, and 
further reduce the potential for the formation of 
condensation between the wall and the new window,
it is essential that the rough opening gap doesn’t
allow air and moisture to pass between the new 
window and the existing wall into the opening cavity.
1. Sealant Method: Apply Caulk/Sealant to the
interior side of the rough opening in a continuous
manner to provide an even, unbroken sealant bead
sufficient to fill the gap between the new window and
the rough opening.  Where needed, foam or rubber
backer rod can be used as a “bond breaker” ensuring
that the sealant only bonds to the window frame and
the rough opening.  
2. The Barrier Tape Method: Tape that is 
impervious to air and moisture, with adhesive of 
sufficient strength to
adhere to wood, vinyl,
metal, or plastic shall
be placed across the
rough opening gap
adhering to the dry
wall on one side of the
gap, and the interior
surface of the window
frame on the other,
or between the new
window frame and the 
left-in-place frame.
Application, Shimming, 
Fastening, and Sealing
EXTERIOR
SEAL
INTERIOR
SEAL
INSULATION
FASTENING
SHIMS
PLUMB/
LEVEL
Jamb 
Extension
Builders
Tape
SAMPLE MANUAL

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