Astragals for Pairs of Doors

What an astragal does

A pair of doors always has a gap where the two leaves meet, called the meeting edge or meeting stile. On a single door the frame stop covers the edges. On a pair there is no frame member in the middle (unless you add a mullion), so the astragal does that job.

• Gap closure: blocks light, drafts and some sound through the meeting edge.
• Smoke and fire: on labeled pairs, an astragal or meeting-edge gasket may be part of the tested assembly.
• Security: an overlapping astragal covers the latch so it cannot be reached with a pry bar or a card.
• A stop for the active leaf: on some pairs the inactive leaf acts as the stop for the active leaf.

Overlapping vs split astragals

The type of astragal changes how the pair operates, so it is a functional decision, not a trim choice.

Astragals on fire-rated pairs

On labeled pairs, whether an astragal is required depends on the door manufacturer's listing for that assembly, not on a single code rule. Some listings require an overlapping astragal; others allow a pair without one when both leaves positively latch, for example with vertical rod exit devices. Check the listing and the label before deleting or adding one.

NFPA 80 also controls the clearance at the meeting edges of fire-rated pairs. The meeting-edge clearance is tight: 1/8 inch with a 1/16 inch tolerance for steel pairs, and 1/8 inch maximum for wood pairs, and an astragal or gasket cannot be used to excuse a gap that is out of tolerance. If the clearance is wrong, the door gets adjusted or replaced.

• Use astragals that are listed for use on the specific labeled door, or that ship from the door manufacturer.
• Field-applied astragals on labeled doors must follow the listing; drilling a labeled door outside its listing can void the label.
• Where positive pressure testing applies (UL 10C), meeting-edge gasketing or intumescent seals may be required by the listing.

Hardware an astragal forces you to coordinate

An overlapping astragal sets up a closing sequence. The inactive leaf must close and latch first, then the active leaf closes against it. Everything on the pair has to respect that order.

• Coordinator: holds the active leaf open until the inactive leaf closes. See the door coordinator guide.
• Flush bolts: automatic or constant latching flush bolts on the inactive leaf usually pair with an overlapping astragal. See flush bolts.
• Closers: both leaves typically get closers on fire-rated pairs, which is why the coordinator becomes necessary.
• Exit devices: check whether the device is listed for use with an astragal, and whether a mullion would be cleaner. See exit devices.
• Locks and strikes: the strike for the active leaf mounts on the inactive leaf, so the inactive leaf needs the right prep and reinforcement.

How to write the astragal into the spec

Astragals get missed because they sit between the door supplier and the hardware supplier. Say who furnishes it. On hollow metal doors it is often factory applied by the door manufacturer; on wood doors it may be factory or hardware. Write it into the hardware set and the door schedule so the submittal shows it.

1. Identify every pair and decide: overlapping, split, mullion, or none.
2. Confirm the fire label requirements for each labeled pair.
3. Match the astragal to the hardware: coordinator, flush bolt type, exit device type.
4. State the furnishing party (door manufacturer or hardware supplier) in the spec.
5. Check finish and material against the door and the rest of the set.

Getting this right across a project is part of door hardware specifications and the door hardware sets they produce.