An astragal is a piece of molding used on a pair of doors or between the top and bottom leaves of a Dutch door, to provide security, protect against weather conditions, prevent light or sound transmission, or to retard the passage of smoke, flame, or gases during a fire. On a Dutch door the astragal is used to close the bottom leaf in conjunction with the top leaf. An astragal should not be confused with a mullion, which sits between (fixed) or behind (removable) the meeting stiles of a pair.
There are two types of astragals – overlapping and split. An overlapping astragal is typically a solid piece of steel, stainless steel, aluminum, or wood, sometimes with an integral piece of gasketing. A split astragal, also called meeting stile gasketing, is a set of two pieces of gasketing that meet in the center to help seal the gap between the doors. While split astragals are sometimes required to limit smoke transmission, some door listings require an overlapping astragal with a 3/4″ projection (typically 3-hour-rated doors).
A conflict arises when an overlapping astragal is required by the door listing, but that astragal would inhibit the free use of the other leaf, particularly when vertical rod exit devices are used. The photo to the right is an example of a door opening with vertical rod panics and an overlapping astragal mounted on the inside of the leaf on the right (the LHR leaf). The door on the left (the RHR leaf) will operate freely, but the leaf on the right can’t be opened unless the other leaf has been opened first. A coordinator would also be required to ensure that the leaf on the right closes first.
For this opening I would have used meeting stile gasketing on the exterior, but if this was a 3-hour rated pair that required an overlapping astragal, I would have used one vertical rod panic, one mortise panic, a coordinator, and a carry bar. The astragal would be attached to the exterior of the door with the mortise panic. Then the door with the mortise panic would operate freely, and the door with the vertical rod panic and carry bar could push the other door open far enough to clear the astragal and allow egress. Functionally, it’s not the ideal application but it’s the best way I know to avoid the conflicts and provide a code-compliant opening.
NFPA 80 – 1999, 2007, 2010
188.8.131.52 Doors swinging in pairs, where located within a means of egress, shall not be equipped
with astragals that inhibit the free use of either leaf.
184.108.40.206 Pairs of doors that require astragals shall have at least one attached in place to project
approximately 3⁄4 in. (19 mm) or as otherwise indicated in the individual published listings.
220.127.116.11.1 Where there is an astragal or projecting latch bolt that prevents the inactive door from
closing and latching before the active door closes and latches, a coordinating device shall be used.
Thank you to George Cutler of Quarters Hardware for the application photo, and to NGP for the graphics.