installing replacement window

Begin by measuring the window to be replaced. Measure at three locations: top, middle and bottom of the window on width, and right, center and left on height. Use the smallest of these measurements to determine the width and height. Do not remove the old window until the dimensions of the new window have been verified to fit the opening properly and you have all the accessories needed.

Accessories are available to ease the installation and finishing of the new window. For more information, contact us.

Remove the old window and prepare the opening (leveling off the sill if necessary). It is important to remember that the replacement window must fit into the opening plumb, level and square, even though the opening may not be any of these. If the window is not plumb, level and square the following problems may occur:

Double Hung and Slider sash may be difficult or impossible to remove.
Casement sash may not operate properly due to excessive drag on the sill.
The sash pivot bar on Double Hung windows could bind and cause the sash to become inoperative.
The overlapping and interlocking meeting rail on Double Hung and Slider windows may not perform properly—allowing air and water infiltration, even if the sash is locked.
The weatherstripping may not seal properly, allowing air and water infiltration.
The partial-ventilation latch on Slider windows may drag on the center leg of the sill or be inoperative.
The locking system may not engage properly.
Place wood blocks along the windowsill. The blocks will help support the window and keep the sill level. Also, wrap the entire perimeter of the window with insulation.
Attach the sill extender (if necessary) to the bottom of the sill and trim it to fit in the opening.

Tilt the window up into the opening with the sash closed and locked. Set it down on the wood blocks placed along the windowsill. Tighten the adjustment devices (alignment clips, jamb adjusters, etc.) and shim the wood blocks to hold the unit secure while checking it for plumb, level, and square.

To check plumb: Place a level vertically on both the interior and face of the left and right jambs. If the bubble indicator is centered, the unit is plumb. To check level: Place a level along the sill. If the bubble indicator is centered, the unit is level. To check square: Measure window frame diagonally. Measure from the top left corner of the frame to the bottom right corner and from the top right to bottom left . If the measurements are equal, the window is square.

Check the sash where they meet the frame to be certain the weatherstripping is sealing properly in all areas. Inspect all weatherstripping to insure it has not pulled out of the receiver channel. To reinstall it, pull the stripping completely out of the channel then reinsert it by sliding the spline into the receiver channel. Check for an even reveal (gap) between the sash and the frame.

Once the window is plumb, level and square, install installation screws (provided by Owens Corning) into the prefabricated installation holes in the jambs. The screws can go through the wood blocks and shims if necessary. DO NOT OVER TIGHTEN THE SCREWS, as this could cause the frame to bow. Recheck the sash for proper operation once the screws have been installed. Caulk and cover the installation holes when necessary.

Note: When installing Casements, place screws in the installation holes. Replace existing screws closest to the center of the sill on both hinge tracks with installation screws (see below).

Replace a screw in each tie bar guide with installation screws. (right) After the window is secured, recheck the sash operation and the weather seals.

With Awnings, replace one of the two screws in the handle assembly with an installation screw (see below).

Replace the second screw from the top and the closest screw to the bottom on the hinge tracks with installation screws. (right)

Install installation screws in the predrilled installation holes in the head. After the window is secure, recheck the sash operation and the weather seals.

If installing large windows or windows with high wind load requirements, install interior and exterior blind stops along the jambs, head and sill (if not already present). The blind stops must be a minimum of 3/4" by 1/2".

Finish off the exterior of the window. Trim the opening and cap off any gaps. Seal the entire perimeter of the window with the proper grade of silicone caulk, but do not caulk over the weep holes.

Finish off the interior of the window. Make certain the sash open and close easily, lift out, lock when closed, and there are no gaps where the sash and frame meet.

Main Installation Instruction Page