Loud Bang From the Garage: What Just Broke
A single loud bang from the garage, followed by a door that will not open, is almost always a torsion spring snapping. The sound is the spring releasing its stored energy against the shaft. Do not use the opener: the springs carry the weight of the door and without them the opener will strain, bend panels, or drop the door.
What you heard
People describe it as a gunshot, a car hitting the house, or something heavy falling over. It is loud, singular, and it comes from the garage.
What happened is that a wound torsion spring, holding a couple of hundred pounds of stored energy, reached the end of its cycle life and let go. The energy discharges against the shaft in a fraction of a second, and the gap in the coil is usually visible from the floor: a clean break with the two halves separated by an inch or two.
The next ten minutes
Do not press the opener button. The springs lift the door, not the motor. Running the opener now will strain the motor, can bend the top section, and can pull the door off the track.
Look at the spring. It runs along the shaft above the door opening. A broken one has an obvious gap. If you can see that gap, you have your answer.
Leave the door where it is if it is closed. This is the good outcome. Your car may be trapped, but nothing is going to get worse overnight.
If the door is open, be careful. Without spring support it is dead weight. Two people can usually bring it down, and it should be done slowly with hands clear of the section joints.
Do not disengage the manual release with the door up. Pulling the release on a raised door with a broken spring lets it drop.
What it costs to fix
| Job | Price |
|---|---|
| One spring replaced | $170 to $400 |
| Both replaced together | Adds $150 to $300 |
| Cables replaced at the same time | $100 to $250 |
| Emergency or after-hours dispatch | $200 to $350 on top |
Whether this is an emergency depends on your situation. Door closed, car outside, and it can wait until morning, which saves you the premium. Car trapped and needed, or door stuck open on an attached house, and it cannot.
Both springs, and why
If your door has two springs, they were installed together and have taken the same number of cycles. The one that did not break is at exactly the same point in its life as the one that did, and in practice it usually follows within a few months.
Replacing both at once costs $150 to $300 more than one rather than double, because the visit and most of the labor are shared. It is one of the few upsells in this trade that is genuinely arithmetic rather than sales.
You can decline it. A company that will not let you decline it is telling you something.
Why it is not a DIY job
A torsion spring is wound to a specific number of quarter turns for the weight of your specific door. Winding and unwinding it takes proper winding bars, and doing it with a screwdriver is how people lose fingers and take blows to the head.
This is not caution for its own sake. It is the single most common serious injury in residential garage door work, and it happens to competent people who underestimated the amount of energy involved.
Related questions
Is a broken spring dangerous once it has snapped?
The spring itself has released its energy and is no longer under tension. The danger is now the door, which is dead weight with nothing holding it up. Do not stand under it and do not lift it without help and something to prop it.
Could it have been something else?
A cable snapping makes a sharper, lighter crack and usually leaves the door crooked rather than immovable. A bang with the door then refusing to lift is the spring in the large majority of cases.
Why did it break now?
Springs fail on cycles, not on age alone. A standard spring is rated for about 10,000 open and close cycles. Cold weather makes steel more brittle, which is why New York sees a clear spike in the first hard freeze of the season.