Rolling Door Bottom Bar

The rolling door bottom bar is a formed steel extrusion bolted across the very bottom edge of a rolling steel door curtain. Because individual curtain slats are relatively narrow and flexible, they cannot by themselves create a stiff, sealed lower edge. The bottom bar solves both problems: it stiffens the last several inches of the curtain and gives installers a stable surface onto which they can attach accessories.

What the bottom bar typically carries:

• Astragal or floor seal: A rubber or vinyl compressible strip that closes the gap between the curtain and the floor when the door is fully down. This limits air, water, and pest infiltration.
• Sensing edge: A pressure-sensitive strip wired to the door operator. If the descending bottom bar contacts a person or object, the sensing edge triggers an immediate reversal. UL 325 requires a contact reversal device on commercial operators, and the bottom bar is how that device is physically installed.
• Lock rod or slide bolt: Some single-service doors use a lock bar centered on the bottom bar and guided through the guides to secure the door from the inside.

On a fire-rated rolling door, the bottom bar is listed as part of the fire assembly. Its dimensions, weight, and attachment method are tested and cannot be field-modified without voiding the listing under NFPA 80.

A damaged bottom bar (bent from a forklift strike, for example) may prevent the door from seating on the floor or may jam in the guide, preventing full closure. Because the bar is attached to the bottom slat rather than the barrel, it can usually be replaced without removing the entire curtain from the hood.