Do Your Doors With Electric Strikes Latch Properly?
Electric strikes are one of the most common types of lock hardware used with card access control systems.
Frequently, electric strikes are used with "cylindrical locks", sometimes called "knob locks". These locks are similar to the type that most people have on their doors at home. One common problem that occurs when cylindrical locks are used with electric strikes is that the "deadlatch" fails to work properly.
The "deadlatch" is a small metal piece that is located at the back of the latch assembly. The purpose of the deadlatch is to prevent the latch from being pushed back with a knife or credit card when the door is closed. When cylindrical locks are used with on doors without electric strikes, the deadlatch rests on the metal strike plate that is mounted on the door frame. The latch itself goes into the hole on the strike plate, but the deadlatch rests on the edge of the hole and is depressed against the strike plate when the door is closed. When the deadlatch is depressed, the latch cannot be pushed back from the outside.
When an electric strike is installed on a door, the electric strike takes the place of the regular strike plate. Electric strikes have a much larger opening or "cavity" than a regular strike plate does. The larger cavity allows the electric strike to work with a variety of different type of locksets and provides a little "wiggle room" to allow the electric strike to operate properly.
When a cylindrical lock is used with an electric strike, the latch enters into the cavity when the door is closed. But what about the deadlatch?
The electric strike is designed so that the deadlatch will rest upon the "lip" or "keeper" that is at the front of the electric strike. Unfortunately, the keeper of the electric strike is usually only about an 1/8" wide. This makes the alignment of the electric strike in relationship to the deadlatch very critical. If the electric strike is not perfectly aligned, the deadlatch will fall into the cavity rather than resting upon the keeper as it is supposed to. This prevents the deadlatch from operating correctly, and allows the latch to be easily pushed back using a knife or credit card. The result: a door that can be very easily opened by an intruder.
When Silva Consultants conducts a security assessment, we find that the deadlatch fails to work properly on as many as 6 out of 10 doors that we examine!
Most electric strike manufacturers recognize that the deadlatching function will not work properly when their electric strikes are used with cylindrical locks. Many manufacturers specifically state in their literature that proper operation of the deadlatch cannot be guaranteed.
In most cases, card readers and electric strikes are used on doors that allow access into high security areas. It is ironic that, in most cases, doors equipped with cylindrical locks and electric strikes are easier to force open than doors with regular manual locks.
What can the security system user do to correct this weakness? Here are a few suggestions:
Examine all doors that have cylindrical locks and electric strikes to determine if the deadlatching function is working properly. Look to see if the deadlatch rests upon the keeper as it is supposed to. If the deadlatch goes into the strike cavity instead of resting on the keeper, the deadlatching function isn't working properly.
If the deadlatch appears to be resting on the keeper, give the door a good hard push and pull. In many cases, this will cause the deadlatch to come off of the keeper and fall into the strike cavity. If this happens, the deadlatch can be easily defeated by an intruder.
If the deadlatching function isn't working properly, or can be easily defeated by pushing or pulling on the door, the first thing to do is to call in a qualified electric hardware installer to examine the door. In many cases, the electric strike or door can be adjusted so that the deadlatch operate correctly.
On outswinging doors, consider the installation of a "latchguard". The latchguard is a metal plate that installs on the outside of the door and protects the latch from tampering. Latchguards cost less than $50 and can be installed by a qualified locksmith.
For high security doors, consider replacing the cylindrical lock with a mortise lock. The deadlatch provided on a mortise lock rests either above or below the electric strike cavity when the door is closed. A mortise lock, when used with a properly installed electric strike, is immune to the deadlatching problem and provides much better security than a cylindrical lock.
For very high security doors, consider using an electric mortise lock instead of an electric strike. Electric mortise locks provide excellent security, and in our opinion, are the best choice for use on high security doors. When building a new facility, or planning an new card access system, consider the use of electric mortise locks wherever possible. The cost of installing electric mortise locks is only slightly higher than the cost of installing electric strikes when the hardware is provided as part of a new construction project.
Have questions about the use of electric strikes or other electric lock hardware? Please contact us.
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Published May, 2016