Quick Summary

Parallel arm is the mounting most people have seen the most and named the least. It is the flat looking arm tucked up against the door face in corridors, schools and hospitals, chosen because nothing sticks out into the space where people walk.

This guide covers how parallel arm mounting differs from the alternatives, why it changes the spring size you need, what the shoe is doing, and which parts to order when something on the arm side fails.

What Is a Parallel Arm Door Closer?

A parallel arm door closer is a surface closer mounted on the push side of the door, with the closer body fixed to the door leaf and the arm running back parallel to the face of the door to a shoe mounted on the underside of the frame head.

The name describes the arm, not the closer. When the door is closed, the arm lies flat along the door rather than standing out at an angle, which is the whole point of the arrangement.

Almost every common surface closer can be mounted in all three positions. What changes is the arm, the shoe and sometimes a bracket or plate, so converting a door from one mounting to another rarely means a new closer.

Parallel Arm, Regular Arm or Top Jamb: How Do the Three Mountings Differ?

The differences come down to which side of the door the closer lives on and where the load is transferred.

Regular arm puts the closer on the pull side of the door, with the arm reaching up to the soffit of the frame. It is the most mechanically efficient arrangement, and it is the one where the arm is most exposed, because it projects out from the door.

Top jamb puts the closer on the frame rather than the door, on the push side. It is used where the door leaf cannot take the closer body, for example on a narrow stile aluminium door, or where the door is a pair of glazed leaves.

Parallel arm puts the closer on the door on the push side, with the arm folded back. It gives the cleanest result in a corridor and it protects the arm, at the cost of efficiency.

Why Does Parallel Arm Mounting Need More Spring Power?

This is the part that surprises people. A door that works perfectly on regular arm mounting can feel weak and fail to latch when the same closer is moved to parallel arm.

The reason is leverage. In parallel arm mounting the arm works at a less favourable angle through most of the swing, so less of the closer spring energy reaches the door as closing force. The closer has not changed. The geometry has.

In practical terms that means you plan for a higher spring setting on a parallel arm installation than you would on the same door with regular arm mounting, and you check that the door still latches under the conditions it actually sees.

That third row is the tension to be aware of. Accessible openings cap the force needed to open an interior hinged door, and parallel arm mounting pushes the spring setting the other way. Where both requirements bite, the answer is usually a correctly sized closer rather than a compromise, and sometimes a power operator. Our closer sizing guide covers how the sizes map to door width and weight.

When Should You Choose Parallel Arm?

Four situations point strongly at parallel arm mounting.

The door opens into a circulation route. A projecting arm in a corridor is both a snag hazard and something people walk into, so folding it flat against the door removes the problem.

The opening sees abuse. Schools, hospitals, back of house areas and anywhere trolleys pass through all shorten the life of an exposed arm. A parallel arm sits out of the way.

The appearance matters. On a visible entrance the flat profile reads as tidier than an arm standing out at an angle.

A stop is needed and there is no room for a separate overhead stop. Parallel arm shoes are available with stop functions built in, which solves two problems with one part.

What Is the Shoe and Why Does It Matter?

The shoe is the bracket that fixes to the underside of the frame head and receives the forearm of the closer arm. On a parallel arm installation it is the part that makes the mounting what it is.

Two things follow from that. First, the shoe is a separate part, so a damaged shoe does not mean a new closer or even a new arm. Second, shoes are not universal, so the closer series has to be identified before ordering.

The shoe is also what carries the stop function on the variants that have one. The arm pushes against a built in stop inside the shoe at the end of the opening swing, so the shoe is doing structural work as well as locating the arm.

What Are Cush-N-Stop and Stop Arms?

These are parallel arm variants with a stop built into the shoe, so the door is prevented from opening past a set angle without a separate overhead stop or a floor stop.

A plain stop arm provides a hard stop. A cush arm cushions the end of the swing rather than stopping it abruptly. A spring cush arm adds a spring to absorb the energy of a door that is thrown open, which is the version specified where abuse is expected.

One caution. A stop built into the arm transfers the force of a door being thrown open into the closer and into its fixings. On a genuinely abusive opening a separate overhead stop alongside a plain arm is often the longer lasting arrangement.

What Is an Extra Duty Arm and When Do You Need One?

An extra duty arm is a heavier parallel arm built for openings where a standard arm will not survive. It is the answer to doors that get kicked, propped, pulled and generally mistreated.

The clue that you need one is the failure history. If the same opening has had arms replaced more than once, the fix is not another standard arm, it is a heavier one, and probably a look at whether the door has a stop at all.

Extra duty arms and stop arm variants are often specified together on the worst openings, because an abused door usually has both an arm problem and a swing control problem.

Do You Need a Mounting Plate or Bracket?

Often, yes, and it is the part most frequently left off an order.

A parallel arm installation sometimes needs a mounting plate to give the closer body something to fix to, particularly where the door construction will not take the fixings directly, or where an existing fixing pattern does not match the new closer.

Drop plates and brackets solve the related problem of frames with a narrow soffit, or doors with glazing stops in the way. These are stocked separately and are series specific like the shoe.

The practical rule when replacing a closer on an existing door is to confirm what is currently fixed to the door and frame before ordering, because the old plate may not suit the new closer and discovering that on site costs a return visit.

What Goes Wrong With Parallel Arm Installations?

The useful habit is to separate arm side problems from closer body problems before ordering anything. An arm, a shoe and a plate are inexpensive parts to change. Our LCN door closer parts guide breaks the assemblies down, and the guide to the four main types of commercial door closer covers where surface closers sit overall.

What Do You Need to Confirm Before Ordering an Arm?

If the closer is being replaced rather than repaired, confirm the size as well. Our LCN closer selection guide covers choosing the unit, installing a commercial door closer covers fitting it, and the door closer parts section covers the components.

About the Author

Security Parts has supplied repair parts for commercial door hardware since 2001, covering Von Duprin, LCN, Schlage, Falcon, Detex and Adams Rite at the component level. Our diagram based lookup exists so a technician can confirm a part before ordering it. This guide was written by the Security Parts team from supplier documentation and the questions our customers bring us.

To match an arm to the closer you already have, browse LCN parts or the door closer parts section, or contact us with the series stamping and we will confirm the arm, shoe and plate together.