Garage Door Bottom Seal Replacement: how the work is done

The bottom seal, called an astragal in the trade, is the flexible strip along the underside of the lowest door section that squashes against the floor when the door closes. On most steel doors it is a U-shaped vinyl or rubber profile whose two edges slide into the channels of a retainer fixed to the bottom rail; on wood doors it is often a flat angled strip nailed in place. Replacing it means matching that retainer and profile, fitting a fresh seal the full width of the door, and confirming it meets the floor in one continuous line so light, drafts, water and pests lose their route in.

Why the old seal failed

The old strip is read for its history before it comes off. Cracks along the fold and a chalky surface point to sun and age. A flattened bulb that no longer springs back is compression set. A torn edge at one end usually means the seal froze to the floor and the opener pulled it free. Chew marks say rodents. A strip that has slid partly out of its channel points to a bent or opened retainer, or to a seal that was slightly the wrong size. Each of these leads to a different choice of material, profile or retainer work, so the new seal is spared the fate of the old one.

Wood doors and nail-on strips

A wood garage door usually carries a flat or angled strip of vinyl or rubber nailed directly to the bottom rail rather than a channel seal. The technician removes the old strip and nails, checks the rail for soft spots and cupping, and treats or dries damp wood as needed. The new strip is positioned so its lip angles toward the outside and touches the floor along the full width, then fastened with galvanized nails or screws at close, even spacing so it cannot ripple. On a rail that follows an uneven floor, the strip's flexibility takes up the difference.

A door that meets the floor in one line

The first thing you notice is the absence of daylight. With the door closed and the lights off, the floor line is dark from one jamb to the other, and the draft that used to move across the floor is much reduced. The door lands softly, because the opener now stops when the seal is gently compressed rather than driving the section into the concrete. Leaves, grit and drifting snow are kept out far more often. If you crouch and look, the new bulb sits evenly along the slab, filling the low corner the old strip used to hover above.