A garage door should come down level and meet the floor along its whole width. If yours leaves a wedge of daylight under one side, sits visibly lower on the left or right, or tilts as it travels, something is out of line. Sometimes that is a worn seal or a sloped slab. Sometimes it is a cable or spring that is no longer carrying its side of the door, and that is the version you need to take seriously.
The question that sorts it out is simple: is the door crooked only when it is closed, or does it tilt while it moves? The answer tells you which group of causes you are looking at.
First: if it tilts while moving, stop using it
If the door leans, lifts one corner first, or binds as it opens or closes, stop running the opener. A door that is not moving level is often riding on one cable, and the opener will keep pulling it until a roller jumps the track or the remaining cable fails. If the door is open, leave it fully open and keep people and cars out from under it. If it is closed, leave it closed.
If you heard a loud bang from the garage before this started, assume a spring has broken and treat the door as unsafe until a technician has seen it.
Crooked only when closed: the usual causes
- The floor is not level. Garage slabs settle and crack, and many were poured with a slope toward the door for drainage. The door is straight; the concrete under it is not.
- The bottom seal is worn, torn, or flattened on one side. The rubber compresses unevenly over the years and leaves a gap at one corner.
- The bottom section or its bracket is bent, often from a bump with a car, a bike, or a mower.
- The opener's down travel stops short, so the door never quite settles onto the low side of the floor.
Tilts while moving: the usual causes
- A cable has stretched, frayed, slipped on its drum, or come off it. This is the most common reason a door rides crooked.
- A spring has broken. On a door with two torsion springs, or with an extension spring on each side, losing one leaves the door lopsided and heavy.
- A drum has slipped on the spring shaft, so one cable winds shorter than the other.
- A track is bent or has shifted on its brackets, so the rollers on one side run higher or bind.
- Rollers on one side are worn or broken, so that side drags and lags behind.
What is safe to check
With the door closed and the opener left alone, look from the floor. Check the gap at each bottom corner. Look along the bottom seal for tears or flattened spots. Lay a straightedge or level on the floor where the door lands to see whether the slab dips. Look up at the cables on both sides: they should be tight, seated on their drums, and roughly matched. Look at the springs for a visible gap in the coil. Look at the tracks for bends or loose brackets.
Take photos of each side, straight on and from the edge. They help the technician arrive with the right parts.
If the cables, springs, and tracks all look normal and the door moves level, the cause is usually the seal or the floor. A worn seal is a routine replacement. A sloped or settled slab can often be handled with a thicker or tapered seal or a threshold strip, and a pro can tell you which fits your door.
What is pro-only, every time
Garage door springs, cables, and the drums the cables wind onto are under high tension. Adjusting, re-seating, or replacing any of them is pro work. The bottom brackets where the cables attach are under that same tension, so do not loosen or remove them either. Do not try to even the door by adding turns to a spring, loosening drum set screws, or shortening a cable.
Do not try to straighten a crooked door by pulling or lifting one side by hand, and do not keep running the opener to see whether it settles. Both can throw the door off its track.
How it gets fixed, and what moves the price
A technician secures the door, then works out whether it is the floor and seal or the cables, springs, drums, and tracks. Cables are usually replaced as a pair, and springs on a two-spring door are usually replaced together so they wear evenly. Once the parts are right, the tech re-balances the door so it holds level at any height and resets the opener's travel.
What moves the price is which of those systems is involved, whether a spring broke and took a cable with it, whether a track or the bottom section is bent, and the size and weight of the door. A seal or a small adjustment sits at the smaller end; cables and springs together are more. You see a qualitative range up front, and the technician confirms the price in person after seeing the door.
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Common questions
Why is there a gap under one side of my garage door?+
If the door moves level and only shows the gap when closed, it is usually a worn bottom seal or a garage floor that slopes or has settled. If the door also tilts as it moves, a cable or spring is the more likely cause, and you should stop using the door until a technician has looked at it.
Is it safe to use a crooked garage door?+
Not if it tilts while it moves. That usually means one cable or spring is no longer carrying its side, and running the opener can throw the door off its track or snap the remaining cable. Leave it where it is, keep people out from under it, and have it checked. A door that is level in motion and only shows a gap at the floor is a lower-risk problem.
Can I level my garage door myself?+
You can replace a worn bottom seal and check the floor, cables, springs, and tracks by eye. You should not adjust the springs, cables, drums, or bottom brackets. They are under high tension, and leveling a door through them is pro work every time.