Bay Windows

A bay is a section or compartment of a building in medieval architecture. It is believed that the term bay window was first used to describe the large bay window that was frequently placed in the bay of a castle's great hall, where a high table or dais stood.


While bay windows can be traced back to medieval times, they did not become popular until the early 1870s. Today, you can stroll down any residential street in San Francisco, and you are sure to find rows and rows of gorgeous Victorian homes with beautiful bay windows.

What Is a Bay Window?

Bay windows, or bow windows, may be technically defined as windows that protrude out into the world, in order to capture the view from an outside wall. Bay and bow windows form a recess on the inside wall, often leaving room for a window seat or even a platform for a wide variety of uses.

Bow windows typically consist of four or more casement windows joined together to form a semicircle, while bay windows are typically three windows joined together to form a polygon or rectangle.

The Benefits of Bay Windows

The center window of a bay window is usually fixed with operating casement or double hung windows on either side. Bay windows are not only noted for their beauty, but are also excellent for small spaces as they make them appear larger. Bay windows also increase the flow of light into a room and, depending on their sizes, some give the illusion of the entire room opening up into the great outdoors.

Types of Bay Windows

There are several types of bay windows available including:

  • Fixed
  • Vented
  • Combination of the two.

Fixed bay windows are windows that cannot be opened, while vented bay windows are those that can be opened. Traditional bay windows typically feature a large picture window surrounded by smaller windows on the sides set at 30, 45, 60, or 90 degrees. Replacement or new construction bay windows are sold in a variety of different materials, ranging from aluminum or composite to wood.

Customized Bay Windows

In addition to rectangular or semicircular shapes, bay windows are also available in special shapes. They can be constructed to resemble just about any geometric shape, from hexagons to trapezoids. Bay windows may be purchased from a variety of manufacturers.