Installing Windows in New Construction

How to Install Windows to Ensure Smooth Operation and Prevent Water and Air Infiltration

By Mark J. Donovan

Installing windows in new construction is much easier than installing a window in a finished home. There’s no house siding or trim to remove and you have easy visibility to the framing members in the wall. Most new windows today have a vinyl or metal nailing flange or fin that wraps around the perimeter of the window that makes window installation a breeze. The nailing flange is approximately 1-1/2 inches wide and is perforated with nailing holes all along its length. The nailing flange also offers the additional benefit of acting as a weather seal to prevent water and air infiltration.

Before installing the new window, compare the window dimensions with the window frame rough opening.

There’s no sense lifting up and attempting to install a large and heavy window into a window opening that’s the wrong size.

To install a window in new construction make sure the rough window opening is clean and free from any debris. Also make sure that the house sheathing is flush with the window opening framing. In addition, make sure the house wrap covers all around the window opening and that any excess house wrap is stapled down to the window framing.

Next place and center the new window into the rough window opening. Make sure the nailing flanges are flush with the house sheathing around all of the window sides.

While another person holds the window in place on the outside of the new construction, square and plumb the window in the opening from the inside using a level. You may need to install a few shims to square and plumb up the window. Also check if the window is square by measuring the diagonals of the window.

Installing a New Window eBook

The two diagonal measurements should be the same. Normally if the window is new, closed, and has a shipping band around its middle it is square.

Once the window is in proper position, fasten the window to the house by nailing it into place along the nailing flange with roofing nails.

Place nails every 4 to 6 inches along the window. Use 1-1/2 inch long roofing nails to ensure deep penetration into the wall studs behind the house sheathing. After nailing the window in place cut away the shipping band usually located around the center of the window and try opening and closing the window. It should open and close freely with little pressure.

Finally, after installing the window, apply a 6 inch wide band of ice and water shield over the nailing flanges for extra protection against water and air infiltration.

Room Addition Bid Sheet

Install the ice and water shield by first doing the bottom side of the window, followed by the vertical sides, and finally the top.

For more help on building a home addition, see’s Home Addition Bid Sheets. Our Home Addition Bid Sheets provide you with the knowledge and information on how to plan a home building project, and what to look for when hiring contractors. They also include detailed cost breakdown tables and spreadsheets for estimating your own new home construction building costs.

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