astragal

An astragal is molding profile composed of a half round surface surrounded by two flat planes (fillets). An astragal is sometimes referred to as a miniature torus. It can be an architectural element used at the top or base of a column, but is also employed as a framing device on furniture and woodwork.

An astragal is commonly used to seal between a pair of doors. Exterior astragals are kerfed for weatherstripping. Also flush head and foot bolt hardware is commonly mortised into the astragal to hold the inactive door in place, when both doors operate, at the top and bottom.

It is related to Moulding.

Also known as “Meeting Stile Seals,” the term can refer to the raised half-round overlap where pairs of doors meet. An astragal is designed to be applied to one or both doors of a pair at their meeting edges (meeting stiles). The astragal closes the clearance gap for the purpose of either providing a weather seal, preventing sound from leaking in or out of a room, minimizing the passage of light between the doors, or retarding the passage of smoke or flame during a fire.

Doors are typically the weakest link in any partition that is designed to block sound. This is often due to poor sealing around the perimeter of the door. Astragals, perimeter gasketing, drop seals and door sweeps can all be used to prevent sound from leaking through cracks around the door perimeter.

References

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