What Are Magnetic Door Locks?

What is a Mag Lock: How Mag Locks Work and When to Use Them

Say your front entrance is a glass storefront door and you'd like employees to badge in instead of carrying keys. Or maybe you have a server room that needs to stay locked, but whoever is inside has to be able to walk right out. We hear about both situations all the time, and a magnetic door lock is often part of the answer.

A magnetic door lock, which most people in the trade just call a mag lock, holds a door closed with an electromagnet instead of a bolt or latch. You'll find them all over commercial buildings because they're simple and they last. They do come with trade-offs, though, and they aren't the right lock for every door. Below, we walk through how they work, how they compare to electric strikes, and what building codes expect when one goes on an exit door.

How Do Mag Locks Work

A mag lock system starts with two main pieces. An electromagnet mounts on the door frame, usually along the top, and a steel armature plate mounts on the door so the two line up when it closes. A power supply keeps a steady, low-voltage current running to the magnet. That current is what holds the door shut.

To let someone through, the system simply cuts the power. That can be triggered by a card reader, keypad, fob, push-to-exit button, or a motion sensor on the exit side. Some setups also include a door position or bond sensor, which tells the system whether the door is actually closed and fully locked.

When power reaches the magnet, it pulls the armature plate tight against the frame and the door won't budge. Swipe a valid card and the power drops for a moment. The magnetic field disappears, the door opens, and once it swings shut again, the magnet re-energizes. There's no bolt or latch inside the lock, so there's very little in it to wear out. That's why you'll see mag locks on doors that get opened hundreds of times a day.

Why Mag Locks for Doors Always Unlock When the Power Goes Out

A door mag lock only stays locked while it has power. Lose the power, and the door releases. Installers call this fail-safe operation, and with a mag lock you don't get to choose it. It's just how magnets work.

The upside is that nobody gets stuck inside during an outage. The downside is that the door stays unsecured until power comes back, unless the system has a backup battery.

Magnetic Locks vs. Electric Strikes

The lock we compare mag locks to most often is the electric strike. An electric strike replaces the metal strike plate in the door frame, and the door keeps its normal lockset and latch. When someone's access is approved, the strike releases and the latch slips past it. Depending on the model, a strike can be set up to stay locked when power is lost (fail-secure) or to unlock (fail-safe).

A mag lock skips the latch entirely. It's mounted on the face of the frame and the door, so there's usually less cutting and prep work involved. That makes it handy on glass and aluminum storefront doors, where the frames are narrow and hard to modify. The catch is that it always unlocks without power, and it needs its own exit devices since there's no handle to release it.

There's no single right answer here. On an exterior door that has to stay locked when the power's out, an electric strike is usually our pick. Glass entrances are a different story. Their frames often don't have room for a strike, and a mag lock goes on much more cleanly. In most cases, we don't settle on one until we've seen the opening in person and talked with the people who use it every day.

Where Magnetic Locks Work Best

Mag locks tend to be a good fit for:

• Glass and aluminum storefront entrances
• Busy doors that see constant traffic
• Double doors that would otherwise need complicated latch hardware
• Server rooms, stockrooms, and records rooms that need controlled entry but free exit
• Doors being added to an existing access control system, since most readers, keypads, and panels work with them

The Drawbacks You Should Know About

The biggest one is power. Without it, the door isn't locked, so any mag lock protecting something important should have a battery or UPS behind it.

Mag locks also need extra hardware on the inside. There's no latch to turn, so the door needs a separate way to release, usually a push button and a motion sensor. That adds some cost to the job.

Alignment matters more than most people expect. If the door starts to sag or the armature plate shifts even slightly, the lock loses some of its grip. Mag locks aren't subtle, either. There's a metal box on the door frame, which some storefronts and offices don't love. And some exterior doors and fire-rated doors are simply better served by other hardware.

Safety and Code Requirements

A mag lock installed the wrong way on an exit door can trap people inside during an emergency. Building and fire codes pay close attention to them for that reason.

The details depend on your building and your local jurisdiction, but a mag lock on an exit door usually needs:

• A motion sensor on the inside that releases the lock as someone walks up
• A push-to-exit button that cuts power to the lock on its own, separate from the access control system
• A connection to the fire alarm so the lock releases when the alarm goes off

Fire-rated doors come with their own latching rules, so a mag lock often can't just be added to one. The local fire marshal has the final word on what's allowed.

A hardware-store kit might hold a door shut, but it won't account for any of this. On every mag lock job we do, the exit devices, alarm connection, and power setup get as much attention as the lock itself.

When Your Mag Lock Isn't Working Right

If your door won't stay locked, opens on its own, or ignores valid cards, the problem usually comes down to power, wiring, alignment, or the access control system. We go through each of those in our post on why magnetic door locks stop working. Our technicians can track down the cause and repair the lock, the power supply, or the door hardware around it.

Frequently Asked Questions

Do magnetic locks unlock when the power goes out?
Yes. A mag lock needs power to stay locked, so it releases during an outage. Adding a battery backup keeps it locked until power returns.

Are magnetic locks secure?
A properly sized and installed mag lock is very hard to force open. When they do fail, it's usually because of installation problems like misalignment, exposed wiring, or no backup power.

How strong is a magnetic door lock?
Commercial mag locks are commonly rated around 600 pounds of holding force for interior doors and 1,200 pounds for higher-security doors. The right one depends on the door and how it's used. 

Should I get a mag lock or an electric strike?
It depends on the door. Mag locks work well on glass doors, double doors, and frames that are hard to modify. Electric strikes are usually the better choice for exterior doors that need to stay locked when the power is out.

Can you put a magnetic lock on a glass door?
Yes, and it's one of the most common places you'll see them. Glass doors often need special mounting brackets.

Why does my door stick for a second after it unlocks?
It could be residual magnetism, which is a small amount of hold that lingers after the power cuts off. Worn parts, the wrong armature hardware, or a power supply issue can make it worse. A technician can check the setup and adjust it.

Can I use a magnetic lock at home?
Mag locks are built mainly for commercial buildings. For most homes, a smart lock or keypad deadbolt makes more sense.

Magnetic Lock Installation in New Braunfels and the Texas Hill Country

Anyone who's run a business in Texas knows the power can go out with little warning, whether it's a summer thunderstorm or the grid getting stretched thin. If your door is secured with a mag lock, a blackout leaves it unlocked. That's why we bring up backup power early in every mag lock job. Our team will also go over what the door needs to meet code on the exit side, including sensors, a push button, and a fire alarm connection.

We've been doing this work in New Braunfels and the Texas Hill Country since 1989. Our team installs and repairs magnetic locks, electric strikes, access control systems, and commercial door hardware for businesses from San Antonio up to South Austin.

Not Sure Which Lock Your Door Needs?

Give us a call or send us a message. We'll come look at the door and frame, ask how your business uses it, and recommend the hardware that fits. Sometimes that's a mag lock, and sometimes it's something else.