Astragal

An astragal is the flexible seal that runs the full width of the bottom section of a garage door, attached to the underside of the bottom rail. When the door closes, the astragal compresses against the garage floor, filling the gap that would otherwise let water, wind, insects, and debris into the garage.

Most residential astragals are made from EPDM rubber or vinyl and have a T-slot or retainer-slot profile. The bottom rail of the door section has a channel (called the astragal retainer) that the astragal slides into from either end, allowing replacement without removing the door section.

Common astragal profiles:

• Bulb seal: A rounded bottom that squashes flat under door weight; good for uneven or slightly rough floors.
• Blade seal: A thin flat wiper; best for very smooth, level concrete.
• T-style: Fits into a T-shaped retainer channel; the most common residential type.

A concrete floor that is not perfectly level creates a real test for an astragal. A worn or stiff astragal may leave gaps at low spots, letting in water during rain. If you see water pooling just inside the door after a heavy rain, the astragal is usually the first thing to inspect.

Astragals wear out faster than most other door components because they contact the floor on every cycle. Lifespan varies with floor texture, climate, and cycle frequency. Replacement is a DIY job that takes about 15 minutes with no tools beyond a flat-blade screwdriver.

The astragal is the bottom element of a full perimeter seal system that also includes jamb seals on the sides and a top seal at the header.