How Magnets Are Used in Door Applications

Magnets are used in doors and door hardware in several ways. They can hold a door closed, keep it open, form a seal, control access or detect when a door has opened. The type of magnet and mounting arrangement will depend on the door, the space available and how the door needs to operate.

How Are Magnets Used in Door Applications?

Magnets That Hold Doors Closed

Magnetic door catches

A magnetic door catch usually consists of a magnet on the frame and a steel strike plate on the door. When the door closes, the magnet holds the plate in place until the door is pulled open.

Ceramic magnets work well for traditional cabinet catches, while neodymium magnets can provide a strong hold from a much smaller magnet. That can be useful where space is limited or the catch needs to be concealed.

Push-to-open latches and screen doors

A magnetic push-to-open latch combines a magnetic catch with a push release mechanism. Pressing the door releases the mechanism and pushes the door outward, with a separate strike plate fitted to the door. Magnetic screen doors use flexible magnetic strip or small magnets along the centre seam of two mesh panels. The magnets bring the two sides together after the door is opened.

Magnets That Hold Doors Open

Door stops and holders

A magnetic door stop uses a magnet fastener on the floor or wall to hold a steel plate on the door. The door stays open until enough force is applied to separate the two.

Round base assemblies are commonly used for this type of application. The magnet sits inside a steel cup, which directs more of the magnetic field towards the exposed face.

Fire door hold-open devices

Fire doors need to close when a fire is detected. Where the applicable code permits it, an approved electromagnetic hold-open device can keep a fire door open and release it when connected to an alarm or smoke detection system, allowing the door closer to shut the door.

Building and fire codes are adopted and enforced by each province and territory. Alberta's fire door guidance, for example, covers self-closing requirements, permitted hold-open arrangements and keeping fire doors unobstructed.

A standard magnetic catch, wedge or hook should never be used as a substitute for approved fire door hardware. Fire door hold-open equipment should be selected and installed by a qualified professional.

Magnets That Seal Doors

The magnetic strip in a fridge door sits inside the gasket. It pulls the gasket against the steel cabinet around the door opening, helping the door close properly and keeping cold air inside. Shower door seals can use paired magnetic profiles along the edges of the glass. Other applications, including refrigeration, cold rooms and cleanrooms, may need specific seal materials and profiles. Check the door manufacturer's specification rather than assuming a general-purpose magnetic strip will be suitable.

Magnets That Lock and Sense Doors

A maglock uses an electromagnet on the frame and a steel armature plate on the door. While the electromagnet is powered, it holds the plate against the magnet. Removing power releases the door.

That describes how the lock itself operates. The complete access-control system still needs to meet the requirements for emergency exit and release. Backup power may also keep a maglock energised during a power outage, so the installation needs to account for this.

Magnetic child safety locks use a spring latch inside a cupboard, with a handheld magnetic key used to release it through the door.

Alarm sensors can pair a small magnet on the door with a reed switch on the frame. Opening the door moves the magnet away from the switch, which then signals the alarm system.

Industrial guard doors can use safety-rated magnetic interlocks as part of a designed machine safety system. These are different from the simple magnetic contacts used for general door or alarm sensing.

Magnets in Sliding and Automatic Doors

Sliding cabinet and pocket doors can use the same type of magnetic catch and steel plate as hinged doors. Automatic and access-controlled sliding doors can also use magnetic components for sensing and locking. A door-position contact can report when the door is closed, while maglocks designed for sliding doors can provide the locking function.

Choosing Magnets for Doors

Heat resistance varies by grade and application, so check the product specifications where heat is a factor.

Pull force is the force needed to separate a magnet from the supplier's test surface, usually a thick, flat steel plate. It gives you a useful starting point, but the same magnet may hold less on an actual door.

Consider how the door will pull away from the magnet, the working gap once everything is fitted, the thickness and type of steel plate, and how much force someone should need to open the door. Paint, misalignment and other materials between the magnet and plate can all reduce the available holding force.

It's worth testing the complete catch on the actual door before mounting it permanently. A catch that is much stronger than necessary can also make the door unnecessarily difficult to open.

Mounting and environment matter too. Round base assemblies are available with plain or countersunk holes and threaded studs, depending on how they need to be attached. Countersunk magnets and assemblies take a matching flat-head screw. Follow the manufacturer's mounting instructions and don't overtighten fasteners, as brittle magnets can crack.

For outdoor or damp applications, look at the protection provided by the complete assembly, including the magnet, coating, housing, fasteners and adhesive.

Not sure what your door needs? Contact Jobmaster Magnets Canada with the door's purpose, available space, working gap, mounting method and environment, and we can help you identify a suitable option.

How to Fit a Magnetic Door Catch

For a cabinet or ordinary interior door, rather than a fire door or safety-critical hardware:

1. Position the catch using the manufacturer's template, allowing for the strike plate and the clearance needed when the door is closed.
2. Mount the magnet body to the frame or cabinet side.
3. Align the strike plate with the catch, mark the mounting holes and secure it to the door.
4. Test the catch. The door should hold securely while still opening without excessive force.
5. If the hold is weak or there is a gap, adjust the mounting position or use a suitable spacer.

Frequently Asked Questions

How strong a magnet do I need for a door?

Start with the rated pull force, then consider the direction of pull, working gap, paint, plate thickness and how much opening force is acceptable. Test the complete arrangement on the actual door where possible.

Do magnetic door locks work in a power outage?

A maglock releases when power to the lock is removed. A backup supply can keep the lock powered during a power outage, so the complete system still needs to provide the emergency release required by the applicable code.

Can magnets hold fire doors open?

Yes, where permitted. An approved electromagnetic hold-open device can be connected to an alarm or detection system so that it releases automatically when required. Ordinary magnetic catches, wedges and hooks shouldn't be used for this purpose. Fire door hardware should be assessed and installed by a qualified professional.

Can I use magnets on a wooden or vinyl door?

Yes. A magnet can be mounted to one side and a steel strike plate to the other using fasteners suitable for the material. Pay attention to the gap between the magnet and plate, as even a small separation can reduce the available holding force.

Do magnets for doors lose strength over time?

Permanent magnets can retain their magnetic properties for many years when used within their intended conditions. If a door catch starts holding less securely, check the gap, alignment, hinges and attachment of the strike plate before assuming the magnet itself has weakened. Excessive heat or physical damage can affect a magnet's performance.

Find the Right Magnets for Your Doors

Jobmaster Magnets Canada supplies neodymium and ceramic magnets, flexible magnetic strip and round base assemblies for a range of door applications. Where a standard part isn't suitable, we can also look at custom magnet solutions.

Tell us what you're trying to achieve, along with the available space, gap and mounting requirements, and we'll help you work out what type of magnet or assembly is likely to suit.