A bay window extrudes from a main exterior wall, forming a space framed by three or more windows. The space may be square, polygonal, or round depending on the type of structure. Traditional bay windows are built with inside angles of 90, 135 and 150 degrees, although there are many custom variations.
Bay windows can be found in architecture dating back to the early English Renaissance, where the idea is thought to have come from large bay rooms placed at the ends of great halls in mansions and castles. A surge in popularity is most notable during the late Victorian and Edwardian periods. In England, bay windows came back into style after the London Building Act of 1894 allowed a change in building regulations requiring windows to be flush with exterior walls. At the same time, bay windows began showing up in America, and became rampant in the West during the California Gold Rush.
Box Bay Window
A box bay uses a 90-degree angle to form a protruding box shape. Traditional box styles have a large bay or double-paned window flanked by a smaller window on each side. A sitting area or shelves may be added to the interior. Box bay structures are often found in kitchens as garden windows.
A bow window is a softer variation of the normally angular bay window. Four or more paned segments follow a rounded semicircle pattern. These types of windows showed up during the Georgian period and became fashionable in Regency-style architecture. Bow windows were popular additions to English country homes because it made a person feel outdoors while in the comfort of the home.
Circle Bay Window
A circle bay structure is a more extreme version of the bow window, joining a combination of windows together into a smooth circular area. They are often wrapped around building corners. Circle bay windows came into vogue during the Gothic era and are popular in master bedroom suites, living rooms, and dining nooks.
Oriel windows are rounded window structures built on the upper levels of a building. They are usually supported by brackets or corbels and do not reach ground level. They originated with the idea of creating an upper-level porch area. Oriel windows became popular during the Gothic Revival and are often found in Arabian architecture, where they are called mashrabiyas.