Highlights
Double-cylinder deadbolts require a key to be used on both sides of the door.
They are more secure than single-cylinder locks.
These types of locks make it more difficult for members of the household to come and go freely.
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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.
Pros of Double-Cylinder Deadbolts
Photo: Mark Herreid / Adobe Stock
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 with a simple twist of the thumb-turn. 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. This type of deadbolt may even offer an additional deterrence for would-be intruders since picking a lock takes longer and can add complexity to the entry. A double-cylinder deadbolt not only offers an additional layer of security, but it’s cost-effective, too. The average cost of a double-cylinder deadbolt is $40 to $80, and you can install them on your own or hire a professional locksmith.
Cons of Double-Cylinder Deadbolts
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:
The 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 the key is lost
Risk of being trapped in your home if the 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. The cost to change locks may be worth it for you to ensure proper 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.
Frequently Asked Questions
A deadbolt is one of the most secure locks you can install on your front door, so it is better in terms of home security than other types of locks. While deadbolts are typically more expensive than a regular lock, they’re still quite cost-effective and provide an additional layer of security that may even deter some intruders.
There are different types of deadbolts. The most common type is a single-cylinder deadbolt, which you may recognize on your front door. This type of lock has a keyhole on the outside and a thumb turn on the inside. A double-cylinder deadbolt has two locking mechanisms and requires a key to engage on the inside as well as the outside.
Yes, it’s possible a burglar can get through a deadbolt. Some types of deadbolts are harder for an intruder to get through, though. For example, a single-cylinder lock only requires breaking a window nearby and simply turning it. While other locks, such as a double-cylinder lock, may offer greater protection and make it harder for an intruder, no deadbolt is 100 percent effective.
