I.
Install wood blocking around the entire opening.
The blocking must be the same height as the
existing aluminum window frame. The blocking must
extend to the interior far enough to provide full
support for the sill of the new window, however may
extend as far to the interior as desired. Set blocking
in sealant against drywall return to prevent air
infiltration.
K.
Cut treated wood or PVC filler to loosely fit the
sill cavities in the existing aluminum frame.
This
filler material will help support the weight of the new
window, but should not prevent water drainage. The
depth of the filler should be the same height as the
tallest leg of the aluminum frame. Cut the sill filler
to fill the entire length of the sill in both cavities. Cut
notches in the sill filler to correspond with the weep
holes of the existing aluminum window frame.
L.
Install the wood filler into the existing aluminum
frame.
Insert the sill filler with the notches over the
existing window weep holes. DO NOT block any
weep holes in the existing window.
J.
Apply sill flashing tape.
Cut a piece of flashing tape
6" longer than the existing aluminum frame width.
Apply the tape bottom over the wood blocking so
it overhangs 1” into the first sill cavity of the existing
aluminum frame and goes up 3" each jamb.
1D
1M
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M.
Install and level sill spacers.
Place 1" wide x 1/4-3/8"
thick spacers on the bottom of the window opening
1/2" from each side and 1/2" back from the interior
surface of where the new window will rest. Spacers
are also required below mullions and at screw anchor
locations.
Note: The depth of the shim should be equal to the
window frame depth minus 1/2". Cut the shim to this
dimension. Place the exterior edge of the shim flush
with the exterior of the existing window. Improper
placement of shims may result in bowing the bottom
of the window.
Wood Filler
Flashing Tape
Wood Blocking
Window Frame Depth minus 1/4"
Flashing Tape
Wood Blocking
Window Frame Depth minus 1/4"
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OPENING PREPARATION
