Mullion
From Wikipedia, the free encyclopedia
- For the village in Cornwall, see Mullion, Cornwall.
A mullion is a framing element which divides adjacent window, door, or glass units. Mullions may be made of any material, but wood and aluminum are most common, although stone is also used in windows. Mullions are vertical and are often confused with transoms, which lay horizontally.
A mullion acts as a structural member, and it carries the dead load of the glass and the wind load acting on the glass to the anchor point and back to the building structure. Mullions vary from small members in doors or small glass areas, to very large and deep structural members in many curtain wall systems.
In the past, mullions were necessary because it was not possible to produce sufficiently large panes of glass. In double-glazed windows, a grid resembling mullions is sometimes sandwiched between the panes as decoration, which is called a false mullion or muntin. A false mullion may also be attached to the front face of the glass for an aesthetic division of the glass because it is more costly to produce and install large quantities of smaller panes of glass.
