Opening preparation – Pella Clad Windows with Flush Flange 81CP0101 User Manual

Page 4

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.

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"

OPENING PREPARATION