Why won't my loading dock door stay up?

A loading dock door that won't stay up is almost always a counterbalance problem. The springs that carry the door's weight have lost tension, worn out or broken, or a cable has slipped or frayed, so the door drifts back down once the operator or your hand lets go. On a busy dock the springs simply run out of cycles. Less often the cause is an operator whose limits or brake need adjusting, or weight added to the door that the springs were never sized for. A drifting dock door should be closed, kept out of forklift traffic and looked at by a trained door technician, because the same springs that should hold it open are what stop it from falling.

Why a dock door should stay where you leave it

Most dock doors are sectional doors on high-lift or vertical-lift track, with torsion springs on a shaft above the opening. Some are rolling steel doors with their springs inside the barrel. Either way, the springs are wound to balance the weight of the door, so a well-adjusted door can be lifted with steady effort and will stay put partway open. DASMA, the trade group for door makers, puts it plainly in its technical data sheet on dock doors: door counterbalancing should keep the door from drifting into the opening where it can be hit by vehicles.

That is the real cost of a dock door that sags. A bottom section hanging a foot into the opening is the first thing a forklift mast or a trailer catches, and a hit door turns a spring repair into a section, track and cable repair.

The usual causes, most common first

• Springs that have lost tension. Torsion springs relax with use. DASMA's sheet on spring cycle life says a spring wound with too few turns results in a door drifting down from its open position over time. A door that used to hold and now creeps down a few inches a day is usually this.
• Springs at the end of their cycle life. DASMA notes that a heavy-use dock door can open and close every hour, around the clock. Springs rated for an ordinary door wear out fast at that pace. A dock door that keeps going weak every year or two may need high cycle springs.
• One broken spring on a two spring door. Many dock doors run two or more springs. If one breaks, the door may still open with the operator but will not hold itself up. Look for a gap in the coils on the shaft above the door.
• A cable that has slipped or frayed. The lift cables carry the spring force to the bottom of the door. A cable that has come off its drum or is fraying leaves one side lower than the other, and the door may hang crooked or drop on that side.
• Weight the springs were not sized for. New windows, heavier insulation, added struts, signs or even several coats of paint can push a door past what its springs were chosen for. DASMA's guidance on adding weight to a door warns this can unbalance the door and damage or break the springs.
• Corrosion. Wash bays, cold docks and doors left open in snow are hard on springs. Rust and corrosion pits cut a spring's life short, which DASMA lists among the usage factors that shorten spring life.

If the door has an operator

On a motor-operated dock door, a door that drifts down after it stops can also point to the operator. A brake or clutch that no longer holds, or open limits set too low, lets the door settle. DASMA's dock door sheet says operators should be properly adjusted for their limits at the floor and the header. A technician tests the door with the operator disconnected first. If the door will not stay up by hand, the problem is the springs or cables, not the motor, and adjusting the operator to hold a heavy door only wears it out faster.

What to do right now

• Close the door, or lower it fully, and keep traffic away from it until it is checked.
• Do not prop the door with a pallet, a pole or a forklift. If it drops off the prop, it comes down with nothing holding it.
• Do not touch the springs, the winding cones or the cable drums. They hold enough stored force to cause a serious injury.
• Note what you see: how far it drifts, whether one side is lower, any loud bang recently, and whether the door has had anything added to it.

If the door is stuck closed and you need the opening, see why a commercial garage door won't open before anyone tries to force it.

Common questions

Why does my dock door go down by itself a little at a time?

That slow creep is the classic sign of springs that have lost tension. The springs no longer hold the full weight of the door, so it settles until it finds a point of balance. Adding tension may help for a while on a sound spring, but a spring that keeps losing tension is near the end of its life.

Can a broken spring make a dock door fall?

Yes. With a spring broken, the remaining spring or the operator is holding far more weight than it should, and a door released by hand can come down hard. Treat any dock door with a broken spring as unsafe until it is repaired.

What is a dock high door?

It is a door set at a raised loading dock, so the warehouse floor sits about level with a trailer bed. DASMA says a loading dock floor is typically 48 inches above grade, and dock door openings typically range from 8 by 8 feet to 10 by 10 feet. See our guide to loading dock door sizes for more.

My dock plate won't stay down. Is that the same problem?

No. A dock plate or leveler that pops back up is a leveler problem, not a door problem. On a mechanical leveler it is usually the hold-down or the springs under the deck; on a hydraulic one, see why a hydraulic dock leveler stops working. Either way, take it out of service until it holds.

How G Brothers helps

G Brothers repairs loading dock doors, rolling steel doors and the dock equipment around them, including dock levelers, seals and bumpers, for warehouses and businesses across Denver, Lakewood and the metro. We work on every brand and operator type, carry stock on the truck for most repairs, dispatch 24/7 for doors that cannot wait, and can send a certificate of insurance, usually within 24 hours. G Brothers is a member of the International Door Association. See loading dock door repair, commercial garage door spring repair and dock leveler repair, or call us to get the door balanced and back in service.

Sources

• DASMA, TDS 182: Technical Considerations for Dock Doors
• DASMA, TDS 190: Factors Affecting Spring Cycle Life
• DASMA, TDS 176: Adding Weight to a Garage Door Assembly