Commercial door problems: what each symptom means and how urgent it is

The door only closes while someone holds the button

Stop and call The door has lost its entrapment protection and is telling you so.

This is designed behaviour, not a broken button. Under UL 325, when a powered door has no working sensing edge or photo eyes, the operator must demand constant pressure on the close control all the way down. DASMA’s rolling sheet door evaluation states it plainly: constant pressure is required “for doors with no sensing edge on door bottom bar, or with no photoelectric eyes, or when sensing devices are not functioning properly.” Behind it is usually a cut coil cord, a dead battery on a wireless edge, or a sensor knocked out of alignment. A door closing on hold-to-run through a working shift is a liability with a motor on it, so it gets a technician, not a new staff habit. The full background is in the safety edges and photo eyes guide.

Source: DASMA Technical Data Sheet #286, Rolling Sheet Door Maintenance and Performance Evaluation (PDF), Electric Door Operation. Checked 7 September 2026. ↑ Back to the list

The door drifts down from open, or slams the last few feet

Stop and call The counterbalance is no longer holding the door’s weight. Keep people and lift traffic from under it.

A commercial door is the heaviest moving thing in the building, and the springs are what make it liftable. DASMA’s sheet on spring cycle life names insufficient winding torque as a cause of “a door drifting down from its open position over time”, and a door that slams its last feet of travel is the same physics with less warning. On side-mounted (jackshaft) operators there is a second, nastier version: if cable tension is lost, cables can leave their drums, and DASMA’s guidance on that configuration warns it can lead to uncontrolled door movement. None of this is adjustable by building staff; spring tension is explicitly a call-for-service item.

Sources: DASMA Technical Data Sheet #190, Factors Affecting Spring Cycle Life (PDF), Installation Factors; DASMA Technical Data Sheet #1501, Standard Lift Garage Doors with Jackshaft Operation (PDF); and DASMA TDS #286 (PDF): “Do NOT try to adjust the spring tension.” Checked 7 September 2026. ↑ Back to the list

The chain hoist or push-up has gotten heavy

Book it The door is measurably out of specification, and the trend only goes one way.

The industry publishes the actual limits: operating force should not exceed 35 pounds on a hand chain, 30 pounds on a manual push-up door, or 25 pounds on crank operation. A door that needs more is burning counterbalance, dragging in its guides, or carrying curtain damage, and if it is motorized, the operator is straining against the same resistance on every cycle. Staff can judge this without instruments: if one person used to run the chain easily and now leans on it, the number has moved. Book it before the operator or the springs pay for it.

Sources: DASMA TDS #286 (PDF), operating force limits; and DASMA Technical Data Sheet #269, Rolling Door Performance Evaluation by a Facility Manager or a Building Superintendent (PDF), 35 lb chain and 25 lb crank figures. Checked 7 September 2026. ↑ Back to the list

The rolling door feels unbalanced partway through its travel

Staff check first On a rolling door this can be normal. What matters is whether it changed.

Here is the honest answer almost nobody gives: a rolling door is not supposed to feel perfectly balanced everywhere. The curtain coils onto itself, so the weight the spring fights changes non-linearly through travel while the spring’s torque is linear. DASMA’s counterbalancing sheet says a spring-balanced rolling door typically balances at two points in its travel, and that a door otherwise out of balance “should be regarded as part of the normal design function”. So the staff check is a comparison, not a feeling: has it changed since last month, does it drift from open, does it need force past the limits above? Yes to any of those is a service call. No to all three is a door being a rolling door.

Source: DASMA Technical Data Sheet #272, Rolling Door Counterbalancing (PDF). Checked 7 September 2026. ↑ Back to the list

A forklift or trailer clipped the door

Stop and call Do not cycle it to “see if it still works”. That is how a repair becomes a replacement.

Impact damage hides. A curtain that took a hit can be creased where you cannot see it, a guide can be sprung out of parallel, and every cycle after the hit feeds the damage: the crease catches, the catch bends the next slat, the door misfeeds and comes out of its guides. On wind-rated doors the stakes are higher, because the rating belongs to the door as an engineered system: DASMA lists slats, wind locks, rivets, bottom bar, guides, assembly bolts and wall fasteners as components that must stay coordinated with the manufacturer, which is why the fix after an impact is assessed and quoted rather than hammered straight on the spot.

Source: DASMA Technical Data Sheet #287, Rolling Door Component Substitution (PDF), wind load rated doors. Checked 7 September 2026. ↑ Back to the list

Slats are bent, or the curtain has started to misfeed

Call today One bad slat recruits its neighbours every time the door rolls.

A bent slat changes how the curtain coils, and the coil is what the whole door rides on. Left alone, the bend works on the slats above and below it and starts steering the curtain against a guide. Caught early it is a slat repair; caught late it is a curtain. One warning from the industry sheet is worth repeating because it looks like a shortcut: slats from another door that have the same general shape “may be, but are not necessarily, interchangeable”, and improperly fitting slats compromise the door’s performance. The repair is matched parts, fitted straight, on a rolling steel service visit.

Source: DASMA TDS #287 (PDF), Slats. Checked 7 September 2026. ↑ Back to the list

A sectional panel is cracked, dented or caved in

Book it Usually a single-panel replacement, not a new door. Sooner if it is the bottom panel.

Sectional doors are built in horizontal sections precisely so one of them can be replaced. We source the matching panel, swap it, and re-check the balance, because a new panel changes the door’s weight and the counterbalance was set for the old one. The urgency check is position: the bottom section carries the cable attachment points, so damage low on the door involving the brackets or cables moves this from “book it” to “stop and call”. Details on the sectional door service page.

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After a windstorm the curtain sits bowed, or proud of one guide

Stop and call Wind that beats the door’s design load leaves damage that finishes on the next cycle.

Doors carry two different wind numbers: the design wind load a closed door must survive while staying intact and safely operable, and the smaller operational wind load it can move under. When a storm exceeds the design load, DASMA describes exactly what you are seeing: the curtain can be pushed out of its guides into the building, or pulled outward from the opening. A door that visibly bowed, or whose curtain edge sits proud of a guide, has been asked for more than it was engineered for, and running it now is how the curtain leaves the guides entirely. Secure the opening, keep traffic off it, and have it inspected before its next cycle.

Source: DASMA Technical Data Sheet #456, High Performance Door Operation Under Wind Load Conditions (PDF). Checked 7 September 2026. ↑ Back to the list

The motor runs but the door does not move

Stop and call Do not keep cycling it. Whatever let go is now the only thing you are testing.

On a sectional door this is usually a stripped or disengaged drive: the operator turns, the door stays. On high-performance doors there is a version that means the safety system worked: an inertia brake, which DASMA’s terminology sheet describes as locking the shaft when it senses overspeed, “preventing it from moving until door can be repaired”. In plain terms, if a spring or drive let go, the brake caught the door before it fell, and it will hold the door hostage until a technician resets it. That is the device doing its job. Repeatedly hitting the button tests nothing and risks the one component currently holding the weight.

Source: DASMA Technical Data Sheet #451, High Performance Door Terminology (PDF), Inertia Brake. Checked 7 September 2026. ↑ Back to the list

The door reverses partway down for no reason

Staff check first The industry has a name for this: nuisance tripping. The cause is usually visible.

DASMA’s operator terminology defines nuisance tripping as normal operation interrupted by false signals triggering the protective sensors. Staff can check the visible half safely: photo eye lenses fogged, splashed or knocked crooked, sunlight or a lift light blinding a receiver, a pallet corner or banding strap drifting through the beam, snow or debris piled where the edge lands. What staff should not do is bypass the device to get the door closed; the sensor is the reason the door will not close on a person. If the eyes look clean and aligned and it still trips, the fix is a technician with the listed replacement part, because a photo eye is only approved on the operator whose manual itemizes it, as the safety devices guide explains. Worth knowing: DASMA’s testing guidance calls for monthly testing of photoelectric sensors on commercial openers, which is exactly the habit that catches this before it strands a shift.

Sources: DASMA Technical Data Sheet #350, Garage Door Operator and Gate Operator Terminology (PDF), Nuisance Tripping; DASMA Technical Data Sheet #364, Installation Location of Photoelectric Sensors (PDF), monthly commercial sensor testing; and DASMA TDS #363 (PDF), operator-and-sensor pairing. Checked 7 September 2026. ↑ Back to the list

The operator trips the breaker, hums, or smells hot

Call today Stop using the door. Electrical faults do not heal, they escalate.

A motor that hums without turning, trips its breaker, or produces that hot-varnish smell is telling you a winding, capacitor or drive is failing, and every further attempt cooks it a little more. Two things are worth knowing while you wait. First, check the obvious once: a tripped breaker, a pulled disconnect, an engaged manual release. Second, the reason commercial operator work is not an odd-jobs task: commercial door operators are built and evaluated to ANSI/CAN/UL 325, the safety standard for door operators, and DASMA’s guidance is to evaluate the performance of electric doors quarterly, which is the cadence that catches a struggling motor before the morning it strands the bay.

Sources: DASMA TDS #350 (PDF), UL 325 scope; and DASMA TDS #286 (PDF), quarterly electric door evaluation. Checked 7 September 2026. ↑ Back to the list

The shutter will not close or lock at closing time

Stop and call An opening that cannot be secured is a security exposure, and it is dispatched first.

Storefront shutters and counter grilles fail at exactly the wrong hour by definition, because closing time is when they get used. Jammed slats, a lock seized against a bent bottom bar, a dead operator on a unit that has no practical manual override: all of them end the same way, with a business that cannot lock up. Say “cannot secure the opening” when you call and it goes to the front of the queue, the same as a bay stuck open. If the shutter is on a storefront we can usually make it secure on the first visit even when a part has to be ordered, which is the difference between one bad evening and a week of them. Details on the shutters and grilles page.

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The leveller bangs or hesitates under the forklift

Book it That is dock equipment asking for service before it stops a trailer.

A leveller that hesitates, drops under load, bangs on contact, or will not seat flush on the trailer bed is wearing in its hydraulics, hold-down or lip hardware, and the yard usually complains about it before it actually fails. Dock levellers, restraints and seals are serviced to their manufacturers’ written manuals rather than to a generic industry sheet, which is why our per-bay log records the make and model of every piece of equipment on the dock, not just the door above it. We service the leveller, seals and bumpers in the same visit as the door: one technician, one invoice, one record for the whole bay. Details on the dock equipment page.

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What is safe for building staff, and what is not

Safe, and genuinely useful: the monthly sensor and edge tests, wiping and sighting photo eyes, watching a full cycle from the control station (the door must be visible from the control switch, per the same industry sheet), comparing this month’s chain effort to last month’s, and writing down what changed and when. Not safe, in plain terms: anything carrying the door’s weight. Springs, cables, drums, brackets and the bottom bar are under tension whether the door is up or down, and DASMA’s maintenance sheet for these doors says both parts plainly: brackets and counterbalance assemblies are under extreme spring tension, and spring adjustment is a call-for-service item. The line between the two lists is exactly where a maintenance program starts earning its keep.

Source: DASMA TDS #286 (PDF), warnings and visibility rule. Checked 7 September 2026.

Who wrote this, and how do you know it is right?

This page is written and kept current by Commercial Garage Doorman, the commercial division of Garage Doorman, an owner-operated door company run day to day by Frank from a base at 6 Chestnut Dr in Grimsby, Ontario, working the industrial corridor between Hamilton and Niagara. These are the causes we find most often behind each symptom, not a diagnosis of your door. More about the company, on the residential division’s site.

The sourcing rule is the part you can check. Nothing technical here rests on our say-so. Every figure and every quoted rule comes from a published technical sheet of DASMA, the Door & Access Systems Manufacturers’ Association, linked beside the claim with the date we last confirmed the document was live and still said what we quote. Where the answer belongs to a specific manufacturer, which is the case for dock leveller internals and operator control boards, we say to work from that manual instead of inventing a general rule.