How to Replace Block Frame Windows without Disturbing Brick or Siding
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How to Replace Block Frame Windows without Disturbing Brick or Siding

October 11, 2019


Refer to the most current installation
instructions on installPella.com for the tools, materials and specific steps
needed to install your Pella product. Always use appropriate personal
protective equipment. Score the paint or varnish between the
window frame and the drywall return or interior trim. If the existing window can be removed by
cutting around the perimeter through the existing nail flange, use this method to
remove the window. Otherwise start by removing the screen. If the sashes or
panels are not removable, remove the glazing bead with a putty knife or small
pry bar. Soften the glazing adhesive with a heat gun. At the same time, press a
deglazing wheel between the glass and sash or frame to separate the glass from
the glazing adhesive. Carefully remove the glass sashes and any division bars.
Refer to the installation instructions for more information on window removal.
Cut through the frame in several places. Use a pry bar and a block of wood to pry
the window frame away from the wall. Clean the existing frame and surrounding
wall to ensure it is dry and free of any dirt, oil or debris. Check the opening, or plumb, and level Confirm that the window will fit in the
opening with 1/4 inch to 3/8 inch space left around all four sides. Confirm that
the window frame is deep enough to extend on to the brick or siding and
permit exterior sealant application. Also, check whether the new window frame will
overlap onto the wall framing far enough to permit the frame screws to be driven
into the framing. If it does not, the interior finished material should be
trimmed back, removed, or a Pella drywall return installation clip can be used. Cut and bend a piece of flashing. Apply sealant across the framing and
edge of sheathing at the top and along the ends. Fasten the flashing to the top, wetting
out the sealant. Continue the sealant down each jamb. For brick, place a bead of sealant along the side of the brick, close to the back edge. For siding. fill the gap where the back of the trim and sheathing meet. Cut two pieces of flashing tape 12
inches longer than the width of the opening. Apply the first piece of
flashing tape over the bottom of the flashing and six inches down each side.
Cover the exposed edge of the drywall return, if applicable. Apply the second
piece of flashing tape across the bottom of the opening and six inches up each
side. If the building wrap is accessible across
the bottom, hold the flashing tape over it. This may require loosening the siding.
Cut two pieces of flashing tape equal to the height of each side. Apply one piece
on each side of the opening. Place and level shims on the sill 1/2
inch from each side, as well as under any mullions. Refer to the installation
instruction for additional shimming requirements. Secure the shims with
roofing nails or flashing tape. Drill pilot holes in the new window frame if
they are not factory pre-drilled. Refer to the installation instructions.
If using Pella drywall return installation clips, secure them to the
opening to align with each pre-drilled hole in the window. Apply a continuous
3/8 inch tall bead of sealant on the surface of the flashing tape that covers
the drywall return, if applicable. Center the window in the opening on the
sill shims. Check to make sure that the window rests against the drywall
return and makes contact with the sealant, if applicable. Place shims and
adjust them according to the installation instructions to make the
window plumb and square and to keep the sash to frame gap, or reveal, consistent. Drive screws at each pre-drilled hole.
Refer to the installation instructions. Check for smooth operation. Refer to the installation instructions and make any necessary adjustments. Use a low pressure
polyurethane window and door insulating foam sealant to create an interior seal.
Read the directions on the can before use. Insert the nozzle or straw two
inches into the space around the window, or one inch if the drywall return is not
present and foam is applied from the interior. Place a 1 inch deep bead of
foam to allow for expansion. Apply sealant where the new window frame
and the drywall return meet, if applicable. Shape, tool and clean any
excess sealant. Insert backing rod in the space between
the window and the siding, or brick, and top flashing. Apply a continuous bead of
Pella window and door installation sealant over the backer rod, sealed
between the window and flashing. Do not seal over the flashing. Shape, tool and
clean any excess sealant.

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  1. Step 2 rough opening verification? Should do that before you rip out. Customer would hate to have a boarded up opening for 4 weeks while you wait for a new window.

  2. What’s a “backer rod”. Maybe we should be very careful not to over tighten the screws so you don’t easily crack the new glass??? Flashing and sealant instructions pretty vague.

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