Garage Door Weather Seal Replacement in Ann Arbor, MI Bottom Seal and Threshold

Four seals, and knowing which one has gone

A door has more than one seal and they fail differently. The bottom seal, or astragal, is a rubber or vinyl profile that either slides into an aluminum retainer along the bottom edge or is nailed to a wooden bottom rail on older doors. The perimeter stop seal is the flexible flap on the jamb trim that the door closes against. A threshold seal is a separate rubber ramp bonded to the slab, working from below rather than from the door. Daylight along the bottom means the astragal; daylight up one side means the stop; water crossing an otherwise sound bottom edge usually means neither. Sorting that first avoids replacing the wrong part, and the rest of the repairs are on the service index.

Why the bottom seal goes first here

Three mechanisms stack up on that one component through a Michigan winter. Meltwater and salted slush run off a car and pool at the threshold, then refreeze overnight and bond the seal to the concrete, so the next open pulls the rubber against the retainer and tears it or drags the whole strip out of the channel. Repeated freeze and thaw cycling stiffens the material until it takes a permanent set and stops recovering its shape. And brine sits in the retainer, which is aluminum, and corrodes it from the inside so the channel loses its grip. A seal that looks intact from four feet away is often already hard, cracked at the folds and holding nothing.

Water under the door is often the slab, not the seal

This is the correction worth making before money is spent. DASMA's technical sheet on water infiltration beneath a sectional door treats rainwater migrating past the bottom edge as a common condition rather than a defect, and its remedies are construction details: a slightly inclined lip or sill sloped 3 to 5 degrees away from the opening, or a rectangular notch cut into the slab below grade, at least half an inch deep and wide enough to take a 2-inch track and a 2-inch section. Neither exists in most older garages here, and behind the alley-served garages of the Old West Side the aprons frequently run flat or pitch back toward the door. No seal holds back standing water on a level slab. A threshold seal is the usual practical answer, and it redirects water rather than guaranteeing a dry floor.

Sealing changes where the water goes, and the city has rules about that

There is a knock-on effect worth thinking about. A threshold seal bonded across the opening dams water at the apron, and in winter that dam becomes ice on the drive and, on a corner lot, potentially on the walk. The city requires residential property owners to clear snow from adjoining public sidewalks within 24 hours after any accumulation greater than an inch, and to treat ice with sand or salt within 18 hours of its forming, with one warning issued per season before fines. Where the apron pitches toward the walk, sealing the door without thinking about drainage moves your problem onto the sidewalk you are responsible for. On the postwar attached garages near Pattengill Elementary, opened in 1957, the drive usually falls to the street and this is less of a concern.

What the job involves

The door is opened and supported, the old profile pulled and the retainer inspected rather than assumed good; a corroded or spread channel gets replaced with the seal because it will not hold a new bulb. The correct profile matters: a T-end bulb, a beaded end, and a U-shaped nail-on strip are not interchangeable, and the section's own width sets the size. Cut length is measured with a small allowance so the ends are not stretched thin at the corners. The slab is checked for high spots that stop a straight seal sitting down. If the door is out of level, the seal will show a wedge of daylight at one end no matter what is fitted, and that is a track and spring issue rather than a rubber one. Related work is covered under insulation upgrades and a door that will not close.