Preparing the Rough Opening

• 1). Check that the rough opening of the window is square, plumb and the sill is level. Be sure that the opening is the correct size of the window frame, plus 3/4 of an inch in height and width.
  
  
• 2). Cut a piece of window flashing tape and apply it to the bottom of the rough opening of the window. Make sure the tape is longer than the opening width by 12 inches and that it overhangs the exterior by 3/4 of an inch.
  
  
• 3). Cut tabs 1-inch wide, a half inch from each corner of the window flashing tape and fold them to the exterior of the window. Press firmly so the tabs adhere to the water-resistive barrier.
  
  
• 4). Cut another piece of flashing tape that's longer than the opening width by 12 inches and apply it to the bottom of the rough opening; assuring that it overlaps the first piece by at least one inch. Make sure the tape doesn't extend past the interior framing.
  
  
• 5). Attach spacers that are 1 inch wide and 3/8 of an inch thick to the bottom of the window opening, half an inch from each side. Add shims, if necessary, to assure that the spacers are level.
  
  

Placing the Window

• 1). Remove the Pella window from the plastic wrap and cardboard packaging, making sure not to open the window or remove the plastic shipping spacers or checkrail bands from the window sash and frame.
  
  
• 2). Fold the installation fin out to 90 degrees, making sure not to tear or remove the fin corners, and then apply a continuous bead of high quality exterior grade polyurethane or silicone sealant to the top and sides of the front opening of the sheathing.
  
  
• 3). Insert the window from outside the home by placing the bottom of the window on the spacers at the bottom of the opening and tilting the top into position. Allowing room for shimming, center the window between the sides of the opening then insert one two-inch nail on each end of the top nailing fin in the hole nearest the corner to hold the window in place.
  
  
• 4). Place shims between the window and both sides of the opening to square and plumb the window. Make sure they're placed in the middle, and 1 inch from the bottom and top of the window. Avoid placing shims elsewhere.
  
  
• 5). Use a tape measure to check the space between the interior front of the window and the interior front of the wall, at several points around the window, to make sure it's equal.
  
  
• 6). Drive two-inch nails into each pre-punched hole in the nailing fin to attach the window to the opening.
  
  

Completing Installation

• 1). Remove the shipping spacers and checkrail bands from the window sash and frame. Check that the Pella window has been installed properly by making sure it tilts correctly and opening and closing it several times. Close and lock the window once properly installed.
  
  
• 2). Install frame expander receptor and frame expander by following the "Frame Expander and Receptor" installation instructions included with the Pella window.
  
  
• 3). Apply low-pressure polyurethane window insulating foam sealant between the window frame and the rough opening, from the interior. Allow eight to 24 hours for the sealant to cure completely.
  
  
• 4). Refer to the Pella window owner's manual to determine how the interior and exterior of the window should be finished and how to properly care for and maintain Pella windows.