Tom Shafer

Bay windows bring the inside out

August 26, 2011

A great way to create a sense of spaciousness inside your home--and aesthetic appeal to the exterior--is by adding a bay, bow or garden window. All of these window styles project from the house, so they actually extend your inside space outward.

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Bay and bow window basics

Bay windows normally project at either a 30° or 45º angle and usually consist of three windows, often a picture window and two end windows known as flankers. The flankers are usually casements or double hung windows.

Bow windows have shallower angles and are created using three, four or five of the same style of window. Garden windows extend two to three feet outward at a 90º angle from the exterior wall and are usually only three to four feet in width.

Several factors influence how far bay and bow windows project from the house:

  1. Width of the opening
  2. Angle of the mullions, which are vertical separators that hold windows together
  3. On bay windows, the width of the flankers
  4. With bow windows, the number of windows

A bay in an opening of six feet with 30º mullions, for example, creates a shallower projection than a bay with 45º mullions.

From inside the bay window

A head and seat board define the interior "ceiling" and "floor" of most bay windows. The seat board is usually composed of stain-grade plywood with insulation beneath, while the head board is often vinyl or aluminum-covered plywood.

Sometimes a walk-in bay window better fits a home's design or the home owner's requirements. A walk-in bay has no seat board, and the ceiling is the height of the room's ceiling. Walk-in windows are most commonly seen in colonial-style homes.

From outside the bay window

However far a bay or bow window projects from the house, it must be supported. The most common method--brackets under the bay--support the window against the house. You can also hang the window from a cable system attached to the roof trusses. The danger of failing to support bay windows is that they can sag, causing the seat board to slope outward, and worse--the window could even fall out of the house.

Finally, you must have a roof cover above the entire window. Without a roof covering, a leak is almost certain to develop. Roofs can be decorative or just functional. Decorative roofs use a wooden roof frame made to fit the dimensions of the window. Decorative roof coverings include shingles, copper, steel and even acrylic.

A bay or bow window, literally, adds another dimension to your home by pushing the room out by a few feet. Put in a bay, bow or garden window, and you can feel like you're outside, even when you're craving the comfort of the cozy indoors.

About the Author

Tom Shafer has decades of experience in window sales, marketing and product development. He's worked closely with window design engineers in testing, design, and building code interpretation. Past employers include United Windows and Doors and Norandex, MI Windows. He currently works at a home improvement retailer.


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