Garage door symptoms
There's a gap under my garage door and I can see daylight
An even gap under a garage door is usually a worn or flattened bottom seal, a quick replacement. A wedge widening toward one corner points to a settled floor or a door hanging out of level, which needs a closer look.
Updated
Switch off the garage light and study the shape of the gap
With the door closed on a bright afternoon, note where daylight shows: an even line, a wedge, a bow in the middle or a strip up one side. A photo of that shape, texted to us from anywhere in the Portland metro, tells us more than a tape measure. If the door also leans in its opening, park it until the lift cables are checked.
Likely causes, most common first
Where the light gets in usually names the cause, and a tired bottom seal sits at the top of the list.
- Most common
The bottom seal is worn, flattened or torn
The sign: Light shows as a thin, fairly even line, and the rubber looks cracked, stiff, chewed or pressed flat where it meets the concrete.
The fix: Fit a new bottom seal sized to the retainer channel, with a new retainer if the old one has split. Garage Door Weather Seal and Threshold Replacement, from $149
- Common
The opener stops the door short of the floor
The sign: The seal looks healthy and the gap is even, but the rubber never squashes against the slab when the door closes.
The fix: Reset the close travel limit and the force setting so the seal compresses without the opener mistaking the floor for an obstruction. Garage Door Opener Repair, from $149
- Common
The slab has settled or was never level
The sign: The section joints run parallel to the header, yet daylight opens into a wedge or dip where the concrete has sunk, cracked or heaved.
The fix: Glue a threshold to the concrete or switch to a taller seal profile, chosen by how far the floor drops away. Garage Door Weather Seal and Threshold Replacement, from $149
- Less common
A lift cable is slack and the door hangs out of level
The sign: The section joints tilt against the header, and one cable looks looser than the other from the floor.
The fix: Rewind or replace the lift cables on their drums, then level and rebalance the door so both corners land together. Garage Door Cable and Drum Repair, from $189
- Less common
The bottom section is bowed
The sign: The seal touches at both ends while light shows in the middle, often after a bumper tap or an opener that pushed down too hard.
The fix: Straighten the section where the steel allows, or swap in a matched bottom section with fresh rubber. Garage Door Panel and Section Replacement, from $449
- Less common
The side seals have curled or the jambs have moved
The sign: A vertical line of light runs up a side, the vinyl flap on the stop molding has stiffened, or the jamb feels soft near the floor.
The fix: Renew the perimeter seal on both jambs and the header, after flagging any rotted jamb wood that needs replacing first. Garage Door Weather Seal and Threshold Replacement, from $149
What you can safely check in two minutes
Four quick looks, none of them near a spring or cable, sort most gaps into seal, floor or door.
- Press along the bottom rubber with a thumb. Rubber that cracks, stays dented or has gone hard is finished.
- Lay a level or straight board on the floor where the door lands to see whether the slab dips.
- From the driveway, compare the section joints with the header. Tilted joints mean the door, not the floor, is out of level.
- Watch the door close under the opener. If the rubber never flattens against the concrete, the close limit is the likely reason.
What the shape of the gap tells you
Each pattern of light points to a different part, so read the gap before buying any rubber.
| What you see | Likely cause | Usual fix |
|---|---|---|
| Even line across the width | Worn seal, or the opener stopping short | New seal or a close-limit reset |
| Wedge toward one corner, joints level | Slab settled or sloped | Threshold or taller seal |
| Wedge toward one corner, joints tilted | Slack cable, door out of level | Cable and balance work |
| Light in the middle only | Bowed bottom section | Straighten or replace the section |
| Vertical strip up a side | Curled perimeter seal or a shifted jamb | New perimeter seal |
Why older Portland garage floors open up gaps
Concrete moves over the decades, and a slab that has cracked or sunk where the door lands leaves a gap no door adjustment can close.
Census figures place nearly half of the housing in the city of Portland in buildings from before 1960. A garage floor poured that long ago has had decades of wet winters to crack, settle or tip toward the driveway.
Rubber only stretches so far. A shallow dip gets squashed full, but a deeper one needs a taller seal profile or a threshold glued down to give the door a level landing.
When the gap means the door should stay parked
Stop running the door and call if the gap shows up alongside any of these.
- One bottom corner sits higher than the other, or the whole door leans in its opening.
- A lift cable at a bottom corner looks frayed, kinked or looser than its partner.
- The gap appeared suddenly after a bang above the door or a bump from a car.
- A roller has slipped out of its track, or a track has pulled away from the wall.
What closing the gap involves
Most gaps close in a single visit, and you see the cause and the posted price before any part is fitted.
Steel doors usually hold the bottom seal in a retainer, so we measure the channel shape and slide in rubber cut to length. Wood doors usually take a seal fastened to the bottom edge, which lets us check that edge for rot while it is bare.
When the floor is at fault, the threshold goes where the closed seal lands. When the door is at fault, cables and balance come first, because new rubber on a tilted door only disguises the problem.
Gap under the door: common questions
Why is the gap under my garage door wider on one side?
Either the floor slopes or the door hangs out of level. Stand back and compare the section joints with the top of the opening. Level joints mean the slab settled, which a threshold or taller seal handles. Tilted joints usually mean a slack cable, so stop using the door until the cables are checked.
Will a taller bottom seal fix a garage door gap on an uneven floor?
For shallow dips, yes, and a threshold takes care of deeper ones. A taller profile squashes into low spots while still compressing evenly on the high side. Once the floor falls away farther than the rubber can follow, the seal hangs in the air over the low spot and a threshold underneath works better.
Should I adjust the opener to close a gap under my garage door?
Only if the door stops short of the floor, and only the close travel limit. When the rubber never touches the concrete, a small limit change lets it compress. Push the limit too far and many openers read the floor as an obstruction and reverse. If the seal already touches, look at the rubber or the slab instead.
Why can I see daylight along the sides of my closed garage door?
The perimeter seal on the jambs has curled or cracked, or the jamb itself has shifted. That vinyl stop molding carries a flexible flap meant to press against the door face. Sun and age stiffen it, and a jamb rotting near the floor lets the molding drift. We replace the molding and flag jamb wood needing work.
Can I glue down a threshold myself to fix the gap under my garage door?
Plenty of homeowners do, and placement matters more than the adhesive. The strip belongs right under the line where the closed seal meets the floor, on clean, dry concrete, so the door comes down onto it instead of behind it. If the gap is a wedge from a tilted door, a threshold only hides the cable problem.
Does a gap at the bottom of my garage door mean the door needs replacing?
Rarely on its own, because a gap is usually rubber, concrete or an adjustment. Replacement comes up when the bottom section has rotted through, rust has eaten the lower edge so a retainer will not stay fastened, or several sections are bent. Even then, one section can sometimes be swapped if the model is still made.
Related pages
Areas we cover for this
Calls about a gap under the door come in from Hazel Dell, Milwaukie, Richmond and Division and every other part of the metro we serve.
Ready to get the door moving again?
Call with the symptom, or text a photo of the door and the opener, and we will name the part and the posted price before anyone drives out.