What is Mullion ?

Definition of Mullion in Construction

Term used for the vertical portion of a window or door framing system.

A mullion is the supporting component of a storefront glazed facade, the vertical component of a window system, etc. The term mullion is a reference to any type of aluminum, wood, metal, synthetic support that is supportive of a facade system. The design of the mullion system for a window wall building is very important. Lateral forces caused by wind can generate tremendous force over large surface areas of glass. This force must be transferred by the mullion system to the actual structure of the building. This transfer of forces is accomplished in a number of ways from the use of angles, inserts, support metal, drilled anchors, etc . connecting the mullion system to the actual building structure. Failure of mullion systems can contribute to expensive property losses as well as loss of life. In the South Florida area the wind requirements are what the locals call Miami Dade codes. Many window and door manufacturers cannot comply with the Miami Dade requirements and supply product all over the country, but not in Miami Dade. The dimensions as well as the thicknesses of the mullion systems is substantially heavier than the mullion systems in other parts of the country.