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?

• • • • • • • • • • • • • • • • • • • • • • •

  To learn more about doors and windows, see these other blog posts:

What causes sweating (condensation) on the inside of windows in the winter? 

Is every exterior door of a house required to have a landing outside? 

 What are the small slots at the bottom of the outside of my window? 

Why does condensation form on the outside of some windows and not others in the morning? 

Why if the garage door track a white tube? 

What is the raised metal plate on the floor under the garage door?

 Why do I have to hold down the button to close the garage door? 

 Where is safety/tempered glass required for the windows of a house?

How can I tell if a window or glass door is safety glass? 

Why is pressure washing double pane windows an expensive mistake? 

How many exit doors are required for a house?

 How many exit doors are required for a mobile/manufactured home? 

Are openable windows required to have window screens? Will windows with no screens pass a home inspection? 

Can a bedroom door open into the garage?

What are the building code requirements for a door from the garage to the house?

What is "low-E" window glass? 

What does ANSI 297.1 on glass mean?

How can I check my garage door to make sure it is safe?  

What is an egress window?

Does a home inspector test all the windows and doors in a home? 

How difficult is it to change a window to french doors or a sliding glass door?

How do you determine if a door is left-handed or right-handed?

Why are window security bars dangerous? 

What are the common problems you find inspecting windows?

What is causing a foggy haze on my windows? 

What do those numbers on the manufacturer's stickers in new windows mean?

What does a home inspector check on an electric garage door? 

• What is the tempered label on glass at windows and sliding glass doors called?

• Do I need to have two exterior exit doors in my house? 

• When is safety glass required for windows at stairs and stair landings?

    Visit our DOORS AND WINDOWS and SAFETY pages for other related blog posts on this subject, or go to the INDEX for a complete listing of all our articles.


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