What is an Astragal?

An astragal is a molding or strip that is used to close gaps in a door opening. They can be used to cover the space between a pair of doors between the top of a door and a flush transom panel where there is no mullion, or between the top and bottom leaves of a Dutch door. For fire rated Dutch doors, astragals are required to ensure both the upper and lower leaves close at the same time. Astragals can also be used on single doors when specified, overlapping the frame face for security purposes.

When using an overlapping astragal, a solid piece of steel, aluminum, wood, or other material is attached to one leaf to cover the gap, occasionally with a piece of gasketing. On pairs of doors, these types of astragals prevent both doors from being active; one door must be opened before the other and they must be closed in the correct sequence to fully shut.