How to Install an Extension Jamb on Andersen Windows

Extensions jambs are installed along the sides of windows. They are used to build out the frame opening for windows installed on houses with 2-by-6 walls. These walls are thicker than the more common 2-by-4 walls and window jambs need to be built out so they are flush with the wall. Andersen makes window extension jambs specific for their type of windows. The jambs can be added onto the windows in just a few simple steps before window installation takes place.

Things You'll Need

Pencil
Miter saw
Drill

Drill bit
Screws
Safety goggles

Instructions

- 1
  Place the extension jambs into position on the sides of the window. Mark with a pencil on the extension jamb where the top of the jamb ends. Repeat the process for the jamb on the other side.
- 2
  Slide the jambs into a miter saw. Turn the blade to 90 degrees. Line up the blade with the mark on the saw, turn on the saw and pull down on the lever. Cut straight through the mark on the jamb. Release the lever to stop the blade. Repeat the process for the second jamb.
- 3
  Pre-drill holes into the extension jambs with a 1/8-inch drill bit. Insert a hole three inches from each end and every 12 inches in between. Drill a 3/32-inch hole through the middle of the interior edge of the jamb. Counter-bore the jamb with a 7/32-inch drill bit.
- 4
  Position the extension jambs in place along the jambs of the window. Secure them in place with 1-1/2-inch pan head screws through the pre-drilled holes. Pre-drill the corners of the extension jamb with a 1/8-inch drill bit and secure the corners in place with 1-5/8-inch trim screws.

Andersen Windows Installation

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