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Installation instructions for new construction windows


These installation instructions require that some type of weather resistant "house wrap" has been installed on the exterior of the sheathing prior to the installation of the windows. Installation directly against the sheathing is not recommended. Additional materials needed to complete the installation are: silicon caulking, 6" wide (minimum) membrane water barrier tape, shimming material, 2" galvanized or stainless steel screws for installation. (Horse shoe PVC shims preffered).

Construction of the Opening

New construction window openings must be square, plumb, level, using materials that are free of warps, twists, etc. Check opening for squareness by measuring the diagonals as shown to the right. The opening is square if the measurements are the same. The opening should be 1" larger than the tip to tip window frame size to allow for any necessary shimming. 

IMPORTANT - be sure the construction of the opening meets all applicable building codes and standards. 

Preparation of the Opening

1.Cut the house wrap material that covers the window opening using

the modifed “I” pattern shown to the left. Fold the wrap back into

the opening, stapling it to the framing and trimming the excess material.

2.Next make diagonal cuts in the house wrap 10-12” long at the two upper

corners of the opening to create a fap that will go over the head of the window, as shown to the right. Tape this fap up and out of the way for now.

3.Apply one strip of membrane tape along the edge of the opening at this sill as shown, extending it 10-12” past the corners. Apply a second strip overlapping the frst one that turns into the opening, covering the sill plate. Run this strip up the sides of the opening for several inches as well, notching at the corners.

NOTE – always be conscious of the sequence of these installation steps. 

Flashing is always applied from the bottom up, in “weatherboard” fashion.

Installation of Window

1.Apply a generous bead of silicone caulking to both sides and the top

of the nail fn. Do not apply silicon to the bottom fn. (typical for all new construction windows)

2.Place the window in the opening and press it frmly against the wall

to squeeze the caulking under the fn. Secure to the wall in a temporary

fashion to allow for shimming and leveling of the frame.

3.Shim under the window sill as needed to level the unit(s) in the opening,following the general guidelines shown to the right. Use tapered shims in pairs to create a parallel spacer.

4.Next shim along the sides of the window to ensure there is no bow or twist in the window jambs. Check the function of the window throughout this step to maintain the smooth operation of the sashes.

5.Complete the attachment of the window frame to the exterior sheathing of the house using screws 16” on center around the entire perimeter of the window.

6.Apply membrane strips over the nail fns on the window jamb and head

as shown to the right. First apply the two strips marked 1 along the windowjambs. This material should extend below the membrane strip at the window sill, and up to the bottom edge of the fap of house wrap material at the headof the window. These strips should be at least 6” wide. Next apply another strip over the nail fn at the head of the window. (marked 2). Overlap the jamb pieces by at least 3” on both ends.

7.Remove the tape holding up the fap of house wrap material and let it

overlap the membrane tape strip over the head of the window.

Using the seam tape specifed by the house wrap manufacturer, tape

over the diagonal cuts in the house wrap as shown.

8.Install exterior siding or fnish material around the window, utilizing the

integral “J” channel on the window frame if appropriate.

Finish-up and Adjustment

  • Using low expansion spray foam fill the inside cavity between the sides of the window frame and the rough opening being careful not to overstuff this pocket. 

  • Check the operation of the window and make final adjustments as necessary. Pay close attention that the window jambs are not bowed as this will make operation difficult and diminish performance.

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