Installation instructions for new construction windows Installation from exterior using nailing flange
NOTE:
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: silicone caulking, 6" wide (minimum) membrane water barrier tape, shimming material, 2" galvanized or stainless steel screws for installation. (Horse shoe PVC shims preferred).
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 modified “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 flap that will go over the head of the window, as shown to the right. Tape this flap 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 first 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 flange. Do not apply silicon to the bottom flange. (typical for all new construction windows)
2.Place the window in the opening and press it firmly against the wall
to squeeze the caulking under the flange. 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 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 fins on the window jamb and head
as shown to the right. First apply the two strips marked 1 along the window jambs. This material should extend below the membrane strip at the window sill, and up to the bottom edge of the flap of house wrap material at the head of 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 flap of house wrap material and let it
overlap the membrane tape strip over the head of the window.
Using the seam tape specified by the house wrap manufacturer, tape
over the diagonal cuts in the house wrap as shown.
8.Install exterior siding or finish material around the window, utilizing the
integral “J” channel on the window frame if appropriate.
Finish-up and Adjustment
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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.
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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.
Nailing flange installation FAQ
How much larger should the rough opening be?
About 1 inch larger than the tip-to-tip size of the window frame, so you have room to shim. The opening must be square, plumb and level. Check it by measuring both diagonals: they must be the same.
What do I need for the installation?
House wrap already installed on the sheathing, silicone caulking, membrane water barrier tape at least 6 inches wide, shims (horseshoe PVC shims are best) and 2-inch galvanized or stainless steel screws.
Do I caulk the bottom nailing flange?
No. Apply silicone to both sides and the top of the nailing flange, but not to the bottom flange. This applies to all new construction windows.
How far apart should the screws be?
Fasten the frame to the exterior sheathing with screws 16 inches on center around the entire perimeter of the window.
In what order do I apply the flashing?
Always from the bottom up, like weatherboards: membrane tape at the sill first, then strips over the jamb fins, then a strip over the head fin, and finally the house wrap flap over the head.
Nailing flange or mounting straps?
Use a nailing flange when you install the window from the outside into a wall covered with house wrap. Use mounting straps when you install from the inside into an opening sealed with a waterproofing membrane. See installation with mounting straps.
Our windows come with a nailing flange or mounting straps for U.S. construction. Need help with your project? Get a quote or see how we work with builders and contractors.
