What are the parts of a roll up door?

The parts at a glance

DASMA's maintenance sheets for rolling doors name the parts on a drawing of the door: the hood, the headplate brackets, the curtain, the guide assembly, the bottom bar and the sensing edge. The table below adds the smaller parts a technician will ask about, from the floor up.

Part	Where it is	What it does
Bottom bar	The lowest edge of the curtain	Stiffens the bottom of the curtain and carries the floor seal, the lock and any sensing edge
Bottom seal (astragal)	Under the bottom bar	Closes the gap at the floor against drafts, water and pests
Sensing edge	On the bottom bar of a motor door	Tells the motor to stop or reverse when the closing door touches something
Curtain slats	The face of the door	Interlocking steel strips that hook into each other and flex as the curtain coils
Curtain	All the slats together	The moving surface that closes the opening
Endlocks	On the ends of the slats	Stop the slats from sliding sideways out of each other and ride in the guides
Windlocks	On the slat ends at set spacing	Hook the curtain into the guides so wind cannot bow it out
Guides	Steel channels on each side of the opening	Hold the curtain edges as the door travels; stops at the top keep the bottom bar from running out
Wall angles	Behind the guides	Fasten the guides to the jambs
Barrel	Across the top of the opening	The tube the curtain wraps around, with the springs inside it
Counterbalance springs	Inside the barrel	Carry most of the curtain's weight so the door can be lifted by hand or by a small motor
Tension wheel	On one end of the barrel	Sets the spring tension; it should never be turned by anyone but a technician
Headplate brackets	On the wall at each end of the barrel	Hold the barrel, its bearings and the hood
Hood	Over the coiled curtain	Covers the barrel and curtain from weather and hits
Hand chain hoist or crank	At the side of the door	Turns the barrel by hand on doors without a motor, or when the power is out
Motor operator	On the headplate bracket or the wall	Drives the barrel through gears or a sprocket and roller chain, with limit settings for open and closed
Fusible link and governor	On fire-rated doors only	Let the door close on its own in a fire, at a controlled speed

How the parts work together

When the door opens, the barrel turns and the curtain winds onto it, one slat at a time. The springs inside the barrel unwind as the curtain climbs, so the weight they carry drops as the curtain coils. The guides keep the curtain edges in line the whole way, and the endlocks and windlocks keep the slats from sliding out of each other. At the top, the bottom bar meets the stops in the guides. When the door closes, the curtain unwinds, the springs wind up again, and the bottom bar and its seal come to rest on the floor.

DASMA notes that a door in good balance is easy to move near the open and the closed positions and takes the most force through the middle. On a hand chain door, the pull should not go over about 35 pounds, or 25 pounds on a crank. More than that usually points to the springs, which is a call for a technician.

How a roll up door differs from a home garage door

A roll up door has no panels, hinges, rollers or horizontal tracks, and no lifting cables or cable drums. The curtain coils around the barrel instead of riding back along the ceiling, and the springs sit inside the barrel instead of on a shaft above the opening. That is why roll up doors fit storefronts, warehouses and storage units with little room above or behind the opening. For the parts of a sectional door, see the parts of a garage door, and for how the two compare on a building, see sectional vs rolling steel doors.

Which parts wear out first

DASMA's checklist for facility managers looks at a short list of parts, and and they are the parts that wear first:

• Bottom bar and lower slats. Carts, forklifts and bumpers hit them. A bent slat can be swapped on its own; see whether one slat can be replaced.
• Endlocks and windlocks. When they work loose or go missing, the curtain shifts and can leave a guide.
• Guides. A bent guide pinches the curtain, so the door sticks or will not come down. See why a roll up door won't go down.
• Barrel bearings and the drive chain. Dry or worn ones grind and squeal. See what the noise from a roll up door means.
• Springs. They lose tension over the years, and the door gets heavy. See spring tension on a roll up door.
• Bottom seal and sensing edge. The seal flattens and tears, and a sensing edge that is damaged stops the motor door from closing on its own.

What spare parts can be replaced?

Nearly every part on a roll up door can be replaced without replacing the door: slats, endlocks, windlocks, the bottom bar and its seal, guides, the hood, bearings, springs, the hand chain and the operator. The catch is the match. DASMA's sheet on component substitution warns that parts that look the same may not be the same. Slats of the same general shape may not interlock with another maker's slats, a replacement hand chain must be the same type and size, and bolts that carry the curtain's weight must be of equal or greater strength.

Fire-rated rolling doors are stricter. Under NFPA 80, as DASMA explains it, a fire door must be repaired with parts from the maker of that door. Only parts that are not integral to the door, such as fusible links, S-hooks and release devices, may come from elsewhere, and they must carry the same rating. On wind-rated doors, the slats, windlocks, rivets, bottom bar and guides should be replaced in line with the maker's specifications.

The door's maker and model are often on the product safety label on the guide or the curtain, which helps when parts are ordered.

Common questions

Which parts of a roll up door are dangerous to work on?

The barrel, the springs inside it, the tension wheel and the headplate brackets. DASMA warns that the counterbalance and its parts are under extreme spring tension at all times, and that only a trained door technician should adjust or repair them. Watching, cleaning and reporting are safe; turning the tension wheel or unbolting a bracket is not.

Can a roll up door work without an opener?

Yes. Small storage unit doors are pushed up by hand, and larger doors use a hand chain hoist or a crank. A motor door usually has a way to switch to hand operation when the power is out. See how to open a roll up door by hand.

What sizes do roll up doors come in?

From narrow counter doors to service doors many feet wide. The size drives the slat profile, the gauge and the spring. See roll up door sizes.

How often should the parts be checked?

DASMA recommends an inspection and maintenance visit by a trained technician at least once a year, or as the maker says, and a check right after high wind or flooding.

How G Brothers helps

G Brothers repairs and services roll up and rolling steel doors across the Denver metro, from storefronts and warehouses to loading docks and self-storage buildings, on every brand. We carry stock on the truck for most repairs, and when a slat or a fire door part has to come from the maker, we identify the door first so the new part fits. See roll up and rolling steel door repair and storage unit door repair, call (720) 421-6489 or request a free estimate.

Sources

• DASMA, TDS 270: Recommended Rolling Door Maintenance Practices for Building Maintenance Supervisors
• DASMA, TDS 269: Rolling Door Performance Evaluation by a Facility Manager or a Building Superintendent
• DASMA, TDS 287: Rolling Door Component Substitution