Gap Under My Garage Door When It's Closed
A gap under your closed garage door is almost always one of three things: a worn or torn bottom weather seal, an uneven or settled garage floor, or a door stopping short because the opener's travel limits or photo-eye sensors are off. Start with the rubber bottom seal, it's the cheapest and most common fix. If the gap is uneven side to side or the door won't seat fully, look at the floor, the opener's down-limit, and whether a spring or cable has failed.
Step by step
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1
Inspect and replace the bottom weather seal first
The rubber strip along the bottom of the door (the astragal) is the usual culprit. Pull the door down and look for cracks, flat spots, dry rot, or a piece that's pulled loose from its track. A new U- or T-shaped seal slides into the metal retainer on the bottom rail and runs $15-$40 at any home center. Lubricate the channel with a little dish soap, feed the new seal through, and trim to length. This alone fixes most even, full-width gaps.
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2
Check whether the gap is even or uneven
Close the door and eyeball the gap end to end. An even gap across the whole width usually means a worn seal or an opener that's stopping a hair too high. A gap that's bigger on one side means the door is sitting crooked, your floor has settled, or a cable has slipped or stretched. Even gaps are DIY-friendly; uneven gaps usually need either a threshold seal or a pro.
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3
Adjust the opener's down (close) travel limit
If the door stops short and leaves a gap even with a good seal, the opener thinks the floor is higher than it is. Find the down-limit adjustment on the opener motor head (often a screw marked 'down' or 'close,' or +/- buttons on newer LiftMaster/Chamberlain units). Nudge it so the door travels a touch farther down, then test. Move it in small increments, if you go too far the door will hit the floor, bounce, and reverse.
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4
Rule out the photo-eye sensors and a dirty track
The safety sensors near the floor on each side can make a door stop early or refuse to seat if they're misaligned, dirty, or blocked. Wipe the lenses, make sure both are pointing at each other (the indicator lights should be steady, not blinking), and clear any leaves or debris from the bottom of the tracks that could stop the door from closing all the way.
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5
Address a settled or sloped concrete floor
If the door and seal are fine but the slab dips in the middle or at one corner, the gap is the floor's fault, not the door's. The easiest fix is a garage door threshold seal, a thick rubber strip you glue to the concrete that the door presses against when closed. It's great for keeping out rain, leaves, drafts, and mice, and works well alongside the bottom seal for stubborn uneven gaps.
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6
Stop and inspect for spring or cable failure
If the door suddenly started sitting crooked or won't close evenly, look at the springs above the door and the cables running down each side. A gap in a torsion spring, a cable that's frayed, loose, or off its drum, or a door that's heavy and jerky are all signs of a high-tension failure. Don't try to adjust these yourself, the springs and cables are under enough tension to cause serious injury. Disconnect the opener, leave the door alone, and call a technician.
When to call a pro
Call a pro if the gap is uneven because the door hangs crooked, if you heard a loud bang or see a broken spring or frayed/snapped cable, or if adjusting the seal and opener limits doesn't close the gap, those involve high-tension parts that can cause serious injury.
Call (888) 290-7421Frequently asked
How big of a gap under a garage door is normal?
Basically none, when the door is fully closed the bottom seal should compress against the floor and leave no daylight. A small, even gap usually means the rubber seal is worn or the opener is stopping a bit high. Anything more than a thin, even line, or a gap that's bigger on one side, is worth fixing to keep out water, pests, and drafts.
Why is the gap bigger on one side of my garage door?
An uneven gap means the door isn't hanging level. Common causes are a garage floor that's settled or sloped on one side, a lift cable that has stretched or come off its drum, or a broken spring letting one side drop. Floor settling can be handled with a threshold seal, but a cable or spring problem is a high-tension repair you should leave to a pro.
Can I just replace the rubber seal at the bottom myself?
Yes, this is one of the most beginner-friendly garage door repairs. The bottom seal slides into a metal retainer on the bottom of the door, you pull the old one out, lube the channel with soapy water, feed the new seal through, and trim it. A replacement seal costs about $15-$40 and takes most homeowners under an hour with no special tools.
Will a gap under my garage door let in mice and water?
Yes, and that's the main reason to fix it. Even a half-inch gap lets in rain, blowing leaves, drafts that spike your energy bill, and pests like mice and insects, who can squeeze through surprisingly small openings. A fresh bottom seal plus a threshold seal on the floor seals the door tight and keeps the garage dry and critter-free.
Rather leave it to a pro?
Licensed local techs, same-day service, upfront pricing, and a 1-year warranty.