How to Install a Replacement Frame & Sash Windows

Written by mark morris | 13/05/2017
How to Install a Replacement Frame & Sash Windows
Replacing traditional frame-and-sash windows begins with accurate measurements. (Brick building with clock - ready for text or logo image by Rob Hill from

Frame-and-sash windows, more commonly known as double-hung windows, are the traditional style found on most older homes in a wood frame. They also are available in metal, vinyl and fibreglass models that replicate the classic look of pane-over-pane. The window typically is replaced as one piece, rather than separating the upper and lower sashes from the frame, also known as a jamb. The key to a quality replacement window installation lies in accurate measurements.

Use a pry bar to remove the trim around the edges of the window frame, or jamb. This will expose the gap between the wall frame and the window frame. Study this joint. You will find wood shims tightening the gap, and nails or screws through the jamb into the wall frame.

Measure the window jamb -- from outside to outside, top to bottom and side to side. Order your replacement sash-and-frame windows to fit these dimensions. Use the common term "double-hung" when ordering your windows.

Remove the exterior trim with the pry bar. Using a reciprocating saw, cut the fasteners -- either nails or screws -- that are holding the old window in place between the outside of the window jamb and the wall frame. Lay the window inward and lift it from the opening in one piece.

Set the new window, including sashes and frame, centred in the exposed opening. Place a level on the sill of the window. Adjust the pitch side-to-side by driving wedges under the frame of the window to adjust the bubble in the level indicator until it is centred. Drive one nail down through the sill in each corner to secure it.

Reposition the level onto the face of one of the window frame's vertical jambs. Tilt the window in or out, until the bubble is centred. Wedge shims between the window and the wall frame at the top corner on the levelled side to fit the window in place. Nail through the jamb and shims into the frame. Check the level on the opposite side of the window. Shim and nail it.

Test the window by raising and lowering it a few times to ensure proper operation. Test the latch to make sure the window can be locked in the down position for security. Make adjustments as needed. Wedge shims behind both lower side corners and in the centre of both side jambs. Nail through the shims into the frame. Nail through the top of the window jamb into the header above in either corner.

Pull the nails from the old trim out through the back with locking pliers to preserve the face of the trim. Realign the interior and exterior trim with the new jamb. Nail it in place with a finish nail every eight to 10 inches.

Things you need

  • Pry bar
  • Hammer
  • Tape measure
  • Reciprocating saw
  • Replacement window
  • Shims
  • Level
  • 16d nails

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