What Kind of Door Locks Do
Building Codes Require?
Locks on exterior doors are what most people think of when
considering upgrading the level of security of their homes.
Many people assume their local building codes require a minimum
level of quality and security for the door locks installed on
their homes. The fact is most building codes don't even
require a lock on exterior doors, let alone a minimum level
This places the selection of the door lock on the homeowner or
on his or her contractor. Most contractors are not "lock
experts" and they select the locks based on price. That leaves
it to the homeowner to either accept the lock their contractor
gives them or to select one themselves. The homeowner can make a
better selection knowing what to look for and what options are
Door Locks From a Burglar's Perspective
A good way to begin door lock selection is to look at it from
the burglar's perspective. Burglars prefer to break into a home
through a door because it is quick and easy. However, studies
have shown that a good quality lock is a deterrent. When
intruders are interviewed about the selection of a target, many
say seeing quality deadbolt locks on the exterior doors will
cause them to move on to another house.
A burglar can enter the home through a door using several
The door can be left unlocked and the intruder walks
Doors can be kicked in.
Door locks can be picked.
Door locks can be hammered until they fall off.
Doors can be pried open.
Door frames can be spread apart with a spreader bar.
Door locks can be "drilled out" using a power drill.
Intruders will often try to pry off the lock using
pipe wrenches or pliers.
Door lights (glass in the door) and sidelights can
be broken so the intruder can reach in and unlock
Sometimes thieves obtain a copy of the house key
from an acquaintance and use it to unlock the door.
a study by the California Crime Technological Research
Foundation, the most common techniques used by burglars to enter
single-family homes are (from most often used to least often
Through unlocked window or door
Forced entry by impacts
Prying or jimmying
Use of pass key or picking the lock
Entry attempted, but failed
Other or unknown1
These statistics show how important it is to lock your doors and
windows and to install strong door locks. And because most
forced entries use some form of impact to break through the
door, this means impact resistance should be an important aspect
of selecting door locks.
Important Features in Door Locks
Door Lock with a Deadbolt Type Bolt
lock has a bolt that extends from the lock into the strike,
which is mounted into or on the doorframe.
The type of bolt has a great effect on the lock's strength. In
residential construction there are basically two types of bolts
used on exterior doors: latch bolts and deadbolts. Some locks
combine the two bolts into one.
bolt is a spring-loaded, bevel-shaped bolt. The spring keeps the
latch bolt extended. It will retract by turning the door knob or
lever handle. When the door is fully closed, the spring-loaded
bolt extends into the strike plate about 1/4" to 1/2."
There is also
a type of latch bolt called a deadlocking latch bolt which is
more difficult to retract when the door is fully closed. The
deadlocking latch bolt uses an integral plunger on the face of
the bolt that is retracted when the door is closed.
While retracted, the plunger prevents the latch bolt from being
retracted by end pressure. These latch bolts are sometimes
called pick resistant. However, they typically are no larger in
size than a standard latch bolt and they do not extend any
farther into the doorframe strike plate than a latch bolt does.
Deadlocking Latch Bolt
on the other hand, is not spring-loaded nor beveled and must be
manually retracted and extended. A deadbolt extends farther into
the strike plate than a latch bolt: 3/4" to 1". The deadbolt is
rectangular in shape and is larger in section and length than a
latch bolt. The deadbolt is manually operated by either a
thumb-turn or by key.
Door Lock with an ANSI Grade 1
There is a
grading system that measures the security and durability of door
locks. The American National Standards Institute (ANSI) has
standards, developed and maintained by The Builders Hardware
Manufacturers Association Inc. (BHMA), that comparatively
measure the security and durability performance of door locks.
These ANSI standards, using a variety of tests, classify door
locks with a "Grade." Locks that have undergone the testing
required by the ANSI standards are given a grade of 1, 2, or 3,
with Grade 1 being the best.
Install door locks with an
Grade 1 classification.
There are some confusing details to the ANSI
standards that you must be aware of when looking for that Grade
1 door lock. Here are two examples:
Not all Grade
1 locks are equal.
Different types of door locks are tested differently under
standards. But the grade designation system is the same. This
means a Grade 1 bored latch set is not tested as rigorously as a
Grade 1 deadbolt. The following are the ANSI
standards that apply to various types of door lock.
National Standard for Bored and Preassembled Locks and Latches
Bored Latch Set
National Standard for Auxiliary Locks and Associated Products
Auxiliary Locks: Dropbolt, Rim Lock, & Deadbolt
National Standard for Interconnected Locks and Latches ANSI/BHMA
National Standard for Mortise Locks and Latches ANSI/BHMA
A156.2 Standard (Bored and Pre-assembled Locks and Latches) does
not require bolt impact testing while the other three ANSI
standards listed above do. The Bolt Impact Test, which is based
on the Bolt Impact Test in the American Society of Testing and
Standard Test Methods for Security of Swinging Door Assemblies
(F 476), resembles the type of force created by someone trying
to kick in a door.
and latches that fall under the Bored and Pre-assembled Locks
and Latches category do not have deadbolts. The door locks
covered by the other three standards all have or have an option
of having deadbolt type bolts and are all subjected to the Bolt
Impact Test. The key here is to get a Grade 1 door lock that
has a deadbolt type bolt.
important fact to remember is that mortise locks receive both an
operational grade and a security grade from ANSI A156.13.
The other standards listed above give one ANSI
grade classification, a combined performance and security
classification. If you choose a mortise type lock, be sure
the Grade 1 applies to security aspects of the door lock.
ANSI classifications are not a perfect predictor of a lock's
performance, they do provide a way to compare one lock to
Locks That Offer Key Control
control is simply controlling who has copies of keys to your
home. Many door keys can be copied at a local hardware or retail
store. However, many manufacturers now offer locks using keys
that cannot be copied except by certain locksmiths or only by
the manufacturer themselves.
burglaries where the unlawful entry can be traced back to a key,
that was either knowingly or unwittingly provided to the
Having key control can avoid the following scenarios:
In-home help has been fired or quit, but they made
their own copy of your house key
In-home help may have acquaintances who burglarize
homes; they might try to acquire a
key through them
Mechanics may try to make copies of your house key
while working on your car.
locks with key control does not allow anyone to copy keys except
you or whomever you designate.
Key control may require extra effort from the homeowner, such as
a letter to the lock manufacturer or a trip to the locksmith to
get a key made. Also, there is an additional cost due to record
keeping by the manufacturer or locksmith (between $10 and $50
per key). The additional cost and inconvenience should be
weighed against the security benefits.
Lock Features to Look For
Security Strike Plate
-- A strike plate comes with every door lock. Many times these
strike plates are cosmetic and not intended to provide much
security. They come with two, short 3/4" or 1" screws to attach
it to the doorframe and are made of thin gauge metal.
strike plate's attachment to the doorframe is usually the
weakest point in the entire door/doorframe/lock system.
Standard Strike Plate and Screws
strike plates are available. They sometimes come with a heavy
gauge metal reinforcing plate that mounts under the cosmetic
strike plate and come with 3" long screws that secure the strike
to the wall framing, not just to the doorframe jamb.
holes are staggered so the screws don't penetrate into the same
grain of wood in a wood doorframe or wood wall framing member.
The concept of screwing into different wood grains in the
doorframe and wall framing is to make it more difficult to split
the wood doorframe or wall framing when the door is impacted.
This feature should be considered at every exterior door and at
those doors coming from attached garages.
Security Strike Plate and Long Screws
Throw on Deadbolt
-- The throw of the deadbolt is the length that the deadbolt
extends out of the door edge. A minimum throw of 1" is
recommended. Most deadbolt locks have bolts with 1" throws.
Longer throws makes it more difficult to gain entry by spreading
is spread using a spreader bar. The spreader bar is like a long
car jack and is placed between the doorframe. The intention is
to spread the frame enough so that the lock bolts no longer
extend into the strike plates in the doorframe. If this can be
done, the door can be opened while the door is still locked.
This feature should be considered at every exterior door and at
those doors coming from attached garages.
deadbolts come with internal anti-saw pins. The pins spin freely
inside the bolt. If someone tries to break in by sawing off the
deadbolt, the pin will make this difficult because it spins back
and forth with every movement of the saw blade.
-- Burglars can gain entry through a locked door by breaking the
glass in the door light or sidelight, reaching in, and simply
unlocking the door. Many homeowners, in an effort to prevent
this, install double cylinder deadbolt locks with keyholes on
both sides of the door.
double cylinder deadbolts create a fire safety danger to your
Double Cylinder Deadbolt
In the case
of a fire when the family needs to get out of the house quickly,
you don't want to be wasting time looking for the key to unlock
the door. Most building codes do not allow this type of lock on
doors that are used to exit the house for this very reason.
To solve this
conflict between family safety and security, one manufacturer
has developed a deadbolt lock with a feature called a captured
key. On the interior side of the door the deadbolt lock has a
thumb turn that can be removed from the lock, leaving a keyhole.
The idea is when no one is home, there is no need for the
thumb-turn. The last person to leave removes the thumb-turn and
creates a double cylinder deadbolt condition.
thumb-turn cannot be removed without having a key to the lock.
Therefore, small children cannot remove the thumb-turn from the
lock. Also, the thumb-turn can actually be used as a house key.
It is important that whenever anyone is in the home that the
thumb-turn is left in the lock at all times.
Cased Steel & Beveled Casings
-- On a typical deadbolt lock the outside housing of the lock is
called the "casing" or "case." Many lock manufacturers make
their casings out of hardened steel and many make the casing
beveled. The hardened cased steel makes the casing more
resilient against blows from a hammer. Beveling the casing makes
it very difficult to get pliers or pipe wrenches to stay on the
lock when trying to twist it loose.
-- Some intruders know how to drill out a lock. Some
manufacturers combat this by installing hardened steel chips
within the lock housing. When the drill bit hits these steel
chips, it tears up the drill bit.
-- If a dropbolt or rim lock is selected, make sure the lock is
mounted on the door with through bolts.
with Through Bolts and Without
If not, a
forced entry can cause the lock to separate from the door. The
typical dropbolt and rim lock should not be considered as secure
as a deadbolt lock.
Where to Install Locks With
All exterior doors, including the door between an attached
garage and the house, should have a lock with a deadbolt
installed. Also, on any doors from the garage to the outside,
install deadbolt locks.
Remember, the intruder will select the door that looks easiest
to break into and that offers the least chance of being seen.
Doors going into the garage and going from an attached garage
into the house many times offer an intruder the opportunity to
hide from view while they are breaking in. Extra thought should
go into the security at these locations.
Additional help can be found . . .
Selecting the right door locks and knowing where to install them
is only part of a physical security plan for your home. When
considering security at exterior doors, the strength of the door
and doorframe are just as important as the strength of the door
lock. Read those articles for more information.
Help in assessing the need for better security can be found with
your local police department. Many departments have a crime
prevention unit that will examine your home. Based on their
experience with crime, they can see things that the average
homeowner does not. Also, an experienced locksmith can help you
select the right products.
X4 of ASTM F476-84 (Reapproved 1991) Standard Test Methods for
Security of Swinging Door Assemblies; American Society for
Testing and Materials
State FarmŽ believes the
information contained in the Disaster Survival House is reliable
and accurate. We cannot, however, guarantee the performance of
all items demonstrated or described in all situations. Always
consult an experienced contractor or other expert to determine
the best application of these ideas or products in your home.