Are Double-Keyed Deadbolt Locks Safe?

Scott Dylan Westerlund
Updated September 27, 2021
Person unlocking the deadbolt on front door
Benjamin Gelman -

While many choose double-cylinder locks for security, this option comes with risks

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Homeowners commonly install double-keyed (double-cylinder) deadbolt locks as security features on exterior doors. However, if you’re considering installing one, you need to do your research concerning double-cylinder deadbolt safety. Make sure this lock upgrade is right for you by learning all the risks—and rewards—of double-keyed deadbolt locks.

What's the Difference Between Single-Keyed and Double-Keyed Deadbolts?

The most common type of deadbolt, the single-keyed deadbolt, only requires a key for entry from the outside. The inside of the deadbolt features a knob that locks and unlocks the door.

A double-cylinder deadbolt has key-entry locks on both sides. That means someone inside a house with a double-keyed deadbolt lock is staring at a keyhole in the spot where a person with a single-key deadbolt would see a knob. You’ll need a key to lock and unlock the door from the interior and exterior.

The cost to install a double-keyed deadbolt isn't necessarily more expensive than a single-keyed deadbolt because the installation process is essentially the same.

Why People Choose Double-Cylinder Deadbolts

Security is the main reason why some people opt for double-sided deadbolts. Technically, with a single-keyed deadbolt, a persistent intruder could break a glass window to reach inside to unlock the deadbolt using the knob. This situation can’t happen with a double-sided deadbolt if the key isn't in the interior key slot.

Many caregivers may also opt for double-sided deadbolts as an added security measure because no one is able to leave through that door without a key once the deadbolt is locked.

Key in interior side of deadbolt
Mark Herreid -

Double-Cylinder Deadbolt Safety Concerns

The same features that make double-keyed deadbolts attractive to people seeking added security can make them dangerous in emergencies. Here's a rundown of what to know:

  • Interior side requires a key to open the door when it is locked

  • Must locate key when evacuating in fires and other emergencies

  • Risk of being trapped in your home if key is lost

  • Risk of being trapped in your home if lock jams or breaks

  • Easier to get locked out of your home

Double-cylinder deadbolt locks are not considered safe for emergency exits. Some safety experts don't believe they belong in residential homes at all. In fact, double-keyed deadbolts are actually illegal in some places. This can vary by your:

  • City

  • State

  • Dwelling type

In some dwellings, fire code dictates that double-keyed deadbolts cannot be used on egress doors. It's especially important to consider the liability of using double-keyed deadbolts in rental properties. Be sure to check local regulations before installing such a lock.

Should You Add a Double-Keyed Deadbolt to Your Home?

First, confirm what type of lock you're legally allowed to add to your home by looking at local and state laws. While there is no federal law prohibiting deadbolts requiring two keys, you could violate local codes if you upgrade to a double-keyed deadbolt on even just one door in your home.

If you have a unique situation where you feel that a double-sided deadbolt is the safest option available, consider bringing in a certified local locksmith or door installer to oversee the deadbolt installation. 

When installing a deadbolt that may increase the risk of being trapped in your home during an emergency, you want to make sure that everything is installed based on code requirements and manufacturer standards to prevent any malfunctions that could cause the lock to stick. If you install this or any lock, be sure to talk with everyone in your home about how to operate it in case of an emergency.

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