How to Install Bow Windows

October 11, 2010

Like all windows, bow windows need to be installed correctly in order to function properly and perform as warrantied. Although they are usually larger than most other types of windows, bow windows can be installed by a competent DIY'er and a few helpers.

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Follow the window manufacturer's detailed installation instructions and these general guidelines:

  1. Once the new window has been delivered, you should make sure it arrived with all the necessary hardware and instruction manuals and is in good condition.
  2. When you remove the old window, confirm your new bow window fits inside the existing window opening. Ideally you should have at least 1/4 of an inch of clearance around the top and both sides of the window.
  3. Prep the window opening by first wrapping the bottom sill and then the sides of the opening with a building wrap, such as Tyvek. When you overlap the corners make sure water can shed down the wall without penetrating the protective wrap.
  4. Follow the window manufacturer's instructions and create a sill pan for the window opening, usually made by wrapping the window sill with a self-adhesive flashing tape.
  5. Apply a bead of silicone caulk to the wall around the window opening, and make sure the nailing flange on the window will cover the caulk when the window is installed, creating a weather tight seal.
  6. Install the window into the opening. Bow windows are heavy and usually require at least three people to lift them in place.
  7. Make sure the window is level and plumb once your window is centered, and don't forget to shim when necessary.
  8. Nail the window into place according to the manufacturer's specifications, afterwards covering the nailing flange with self adhesive flashing tape. Install any cables, hangers, or other mounting hardware as directed by the manufacturer.
  9. Bow windows protrude from the wall of the house so special care is needed when attaching the headboard to the overhanging soffit. You may need to build a small roof to cover the top of the window in some instances.
  10. Applying from the inside, use a low expanding foam to insulate the space around the window after it is installed and made weather-tight.
  11. Replace interior and exterior trim, caulking and filling nail holes where necessary.

It is very important to follow the installation instructions which come with the bow window which you purchase. If you do not fully understand how to install bow windows, then seek help from a contractor or professional window installer.

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