What are Mullioned Windows?

Mary McMahon
Mary McMahon

Mullioned windows are windows which are divided into adjacent panes with the use of mullions, which are vertical elements used to break up a space. Mullions are especially associated with Gothic design, and some very fine examples of mullioned doors and windows can be seen in Gothic cathedrals and homes. Many people associate mullioned windows with romantic novels, as people seem to spend a lot of time leaning into or looking out of mullioned windows in this sort of literature, often with fluttering gowns as well.

King's College Chapel at the University of Cambridge is an example of a building with mullioned windows.
King's College Chapel at the University of Cambridge is an example of a building with mullioned windows.

Originally, mullions were structural elements which helped to support the weight of the building around them, in addition to breaking up a window into several panes of glass, which made it less expensive to install. Glass used to be a very costly construction material, and the use of large sheets of glass was uncommon because the biggest panes of glass were used to make mirrors. In addition, construction techniques did not always allow for a huge unsupported opening in a building, making huge glass windows impossible as well as expensive.

Modern mullioned windows may use nonstructural mullions made from a variety of materials, although stone is the classic choice. Wood, metal, and plaster can all be used to create mullions, which may also be made decorative with fanciful painting or carving. If a window is divided horizontally as well as vertically, these horizontal dividers are called transoms.

It is not uncommon to see stained glass installed in mullion windows. Larger mullioned windows may be used to illustrate a brief story or allegory, especially in church architecture. In this sense, the windows are more decorative than functional, since the stained glass obscures the flow of light into the building. The mullion design may also be used on doors, and stone mullions are sometimes installed without glass to ventilate a space such as an enclosed courtyard while still creating a sense of security and privacy.

It is important to distinguish between mullioned windows and windows which are divided into a grid of panes by muntins, sometimes called glazing bars. Mullioned windows often have unusual shapes, and they are frequently arched at the top. Gridded windows are square or rectangular, and the grid is regular, with evenly spaced panes of glass divided into a grid, rather than large blocks of glass divided by mullions or transoms. This grid design is common in sash windows, popular features in Western architecture.

Mary McMahon
Mary McMahon

Ever since she began contributing to the site several years ago, Mary has embraced the exciting challenge of being a wiseGEEK researcher and writer. Mary has a liberal arts degree from Goddard College and spends her free time reading, cooking, and exploring the great outdoors.

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Discussion Comments


Many people forget that it was not the Europeans who introduced mullioned windows, but the Arab populations. One distinct feature of Islamic architecture is the arched windows, which were often inlaid with mullioned windows. Europeans borrowed this style from the Armenians during the Crusades, and the style went well with newly built cathedrals during the Renaissance.

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