How to Install a Bow Window

If you want a window that adds grace and elegance to your home, try a bow window. Like a bay window, a bow window protrudes from the house, but its sashes are in a curve or bow rather than sharp-sided angles such as those seen in bay windows. Other than being heavy and impossible to set into place alone, installing a bow window is a fairly manageable project.

Construct a wall brace made by 2-by-4 inch boards. Place against the ceiling a few feet back from where you want to install the bow window. Construct a header made by two boards at least 2-by-8 inches.

Frame the rough opening for the bow window in accordance with the size of the window you are installing. Place double-studs on either side of the header.

Lift the bow window into the rough opening with the help of a few other people. Level the window by placing shims under the footboard as needed, and nail through extension jambs into the framing studs with tenpenny finishing nails.

Measure height of window, and install rough sill by nailing appropriate-sized studs to the double-studs beneath the header. Nail sill to them. Install "cripples" spaced 16 inches apart beneath the sill.

Secure the cable through screw eyes set into the rafter tails, and tighten the cables. In some cases, you can install exterior knee braces under the bow window for more support.

Run support cables provided by the manufacturer, and in some windows preinstalled, from the bottom of the footboard and up through the headboard.

Install side and bottom flashing to the exterior of the window. Add interior extension jambs. Insulate around the window with fiberglass insulation. Install interior trim.


Some bow windows may need a prefabricated roof if it cannot be tucked under the eaves of the house, or if the house has narrow eaves.

Things You'll Need

  • 2-by-4 inch boards
  • 2-by-8 inch boards (or wider)
  • Shims
  • Circular saw
  • Measuring tape
  • Tenpenny finishing nails
  • Flashing
  • Fiberglass insulation
  • Trim
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