Repairs · Brampton
Garage Door Bottom Seal Replacement
With the door closed and the lights off, a bright line of daylight runs along the floor from one side to the other.
In plain words
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.
How the visit goesThe strip under the door has gone as hard as a hose left out for ten summers. Press it and it does not give; bend it and it cracks. Where the door meets the floor it sits on the concrete without squashing at all.
Garage Door Bottom Seal Replacement
How the visit goes
The floor and the threshold
The concrete under the door is half of the seal. The technician looks at the slope of the driveway toward the opening, the condition of the slab edge where the seal lands, cracks, spalled patches and any step between the slab and the apron. A garage floor that has heaved or settled over the decades is common, and the shape it has taken decides whether a standard seal, a taller bulb profile or a threshold seal glued to the floor gives the most even contact. Where water arrives from outside, the path it takes is noted so the seal and any threshold are placed to meet it.
Fitting a new retainer where needed
If the inspection found a retainer that is bent, corroded or spread open, it is replaced before the seal goes in. The old extrusion is unscrewed or its rivets drilled out, the bottom rail is cleaned and any rust treated, and a new aluminum retainer is fixed straight along the rail with fresh self-drilling screws, checked with a straightedge so the channels run true. Fastener heads are sealed against meltwater. On a door whose channel was moulded into a plastic bottom cap, a screw-on retainer is fitted over the rail so a standard seal can be used from now on.
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.
Garage Door Bottom Seal Replacement
In the van
Threshold seal and adhesive
Aluminum bottom seal retainer
T-style bottom seal
Wire brush and scraper
Bulb or U-style bottom seal
Garage Door Bottom Seal Replacement
What affects the quote
Threshold seal added
Where a floor threshold is recommended, its length, its type, whether rubber or aluminum-backed, the adhesive and the floor preparation before it is laid appear as a line of their own.
Season and conditions
A seal frozen to the slab, ice at the threshold or working in deep cold adds time for freeing the old strip, clearing the line and keeping the new roll warm enough to feed.
Door out of level
If one corner of the door hangs low because of cable or spring tension, levelling the door is separate work done before the seal goes in and is priced on its own.
What to have ready
- What is getting in: light, drafts, water, snow, leaves or pests?
- Is there a car or storage inside that needs moving before the visit?
- Is the gap even across the door, or worse at one end or in the middle?
Garage Door Bottom Seal Replacement: questions
QuestionsWhat does a new bottom seal do about water coming in?
It closes the gap between the door and the slab so rain and meltwater meet a continuous barrier. Where the driveway slopes toward the garage, or the slab edge has dipped, the seal alone is working against gravity, and a threshold seal glued to the floor adds a lip that turns water back toward the drive. The technician looks at where the water comes from and recommends the combination that suits your threshold.
What is a threshold seal, and when is it worth adding?
A threshold seal is a rubber or aluminum-backed strip glued to the garage floor along the line where the door closes. The door's bottom seal lands on it, and its raised outer edge turns water, wind-blown debris and small visitors back toward the driveway. It earns its place where the drive slopes toward the garage, the slab sits below the apron, or the floor edge is too uneven for the bottom seal alone to meet cleanly.
How do I know which size and type my door takes?
Look at the end of the bottom section for the metal or plastic strip that holds the seal. Count the channels, note whether they are slotted or rounded, and measure the distance between them and the width of the door. A photo of the end of the retainer and one of the seal's cross-section is usually enough for the technician to identify the profile before the visit and bring the right roll.
Related services
- Garage Door Tune-UpHalfway up, the door shudders.
- Off-Track Garage Door ResetThe morning after a thaw the opener groaned, the door stayed stuck to the icy floor for a second, then lurched up crooked.
- Garage Door Panel ReplacementAfter an overnight freeze the door stuck to the slab, the opener strained, and something gave.