Why is a double cylinder deadbolt lock on an exterior door a safety hazard?
Friday, July 27, 2018
Getting out of your house quickly at the first sign of a fire is important. One way that the building codes try to make sure that there are no obstacles that would trap you in the house is requiring keyless operation from the interior of any doors to the exterior of the home—called “egress doors” by the building code.
The double cylinder deadbolt needs a key to unlock from both sides of the door and is a defect that we find regularly in our home inspections. It is often installed at an exterior french door because that type of door makes it easy for a burglar to break a glass panel, reach around to unlock a single cylinder deadbolt lock—which has just a thumb-turn lever on inside of the door—and be in the house in a few seconds.
When we mention that the lock is a fire safety hazard, the homeowner invariably points to the key dangling from lock on the inside of the door and says they always leave it in the door, except when they are on vacation. There are two problems with that logic: fire safety should not dependent on remembering to replace a key in a lock and, secondly, when the key is in the lock, it operates as quickly after a glass panel is broken as a thumb-turn lever. What if the one time they forget to put it back is the time they really need it to be there?
If you are concerned about security at an exterior french door, we suggest adding a second keyless interior latch device that is not readily viewable or accessible to someone looking in from the outside.
Also, see our blog post Should a front door swing in or out?
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