Astragal vs. Mullion: What is the difference?

Astragals and Mullions are both associated with double-door openings, but serve different purposes. Understanding the difference between astragal and a mullion can help you choose the correct hardware for your application.

What is an Astragal?

An astragal is a piece of hardware attached directly to one door of a pair of double doors. When the doors close, the astragal covers and seals the gap between them. 

Astragals serve several important functions, including

• Sealing the space between double doors

• Blocking drafts, moisture, dust, and light

• Improving security by covering the gap between doors

• Helping maintain the integrity of fire-rated door assemblies when required

Depending on the application, astragals are available in different styles, including overlapping astragals and meeting stile astragals.

What is a Mullion?

A mullion is a stationary or removable vertical post installed between two doors in the frame. Unlike an astragal, a mullion is attached to the door frame, making them a part of the doorway structure.

Mullions provide structural support and can provide a location for strikes and latching hardware allowing each door to operate independently. 

Depending on the application, a mullion may be either:

• Fixed, remaining permanently installed in the opening

• Removable, allowing it to be taken out temporarily so large equipment can pass through the doorway.

In double doors, removable mullions provide security while allowing the full opening to be used when necessary. 

Knowing the difference between these two components can help you determine which hardware is right for your commercial door application. Consult your Beacon CDL sales representative for direction on the best solution for your specific door application.