Mullion

When an architectural piece divides two or more windows, it's a mullion

Chris HillJanuary 1, 2000

Houzz Contributor. Chris Hill, of chiefs-shop.com, has been woodworking for more than 25 years and has family members who have been involved in nearly every aspect of home building. Chris also builds custom furniture and furnishings and restores and repairs pieces. You can find him on Houzz every week and at http://chiefs-shop.com.

A mullion is an architectural divider that forms a structural, sometimes decorative, divider between two separate window assemblies. A mullion can be integrated into a double-window assembly, or it can be part of the framing of a wall that integrates two adjacent windows.

Chris Hill

The mullion in this illustration matches the casing on the sides.

Replacement Windows

Mullions allow multiple windows to be seamlessly integrated.

Christopher Kellie Design Inc.

Mullions can be wide or, as shown here, narrow.