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Protecting Your Property From Earthquakes
F
EDERAL
E
MERGENCY
M
ANAGEMENT
A
GENCY
A
RE
Y
OU AT
R
ISK
?
If you aren’t sure whether your house is at risk from earthquakes, check with your local building
official, city engineer, or planning and zoning administrator. They can tell you whether you are in an
earthquake hazard area. Also, they usually can tell you how to protect yourself and your house and
property from earthquakes.
W
HAT
Y
OU
C
AN
D
O
Earthquake protection can involve a variety of changes to your house and property – changes that can
vary in complexity and cost. You may be able to make some types of changes yourself. But
complicated or large-scale changes and those that affect the structure of your house or its electrical
wiring and plumbing should be carried out only by a professional contractor licensed to work in your
state, county, or city. One example of earthquake protection is bolting the sill plates of your house to its
foundation to increase structural stability. This is something that only a licensed contractor should do.
B
OLT
S
ILL
P
LATES TO
F
OUNDATION
As shown in the figure, the sill plate of a
house rests directly on top of the foundation.
(This figure shows the sill plate for a house
built on a cripple wall and crawl space
foundation, a type of construction that is
especially susceptible to earthquake
damage.) If the sill plate is not securely
anchored, an earthquake can cause it to shift
on the foundation. When this occurs, there is
a greater potential for severe damage as well
as injury to you and members of your family.
One way to increase the stability of your
house and reduce earthquake damage is to
have the sill plate bolted or otherwise
anchored to the foundation. In the method
shown in the figure, bolts long enough to
pass through the sill plate and penetrate
several inches into the foundation are
installed every few feet along the base of the
exterior walls. This method is not limited to
cripple wall construction; it can also be used
for a house built on a basement or slab-on-
grade foundation or on another type of crawl
space foundation.
EXTERIOR SIDING
SUBFLOOR
FLOOR JOIST
SILL PLATE
FOUNDATION
CRIPPLE WALL
STUD
RETROFIT BOLTS OR
OTHER APPROVED
FASTENERS
Protecting Your Property From Earthquakes
Bolt Sill Plates to Foundation
T
IPS
Keep these points in mind when you have the sill plates bolted to the foundation :
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Modifications to the foundation of your house must be done by a licensed contractor, who will
ensure that the work is done correctly and according to all applicable codes. This is important
for your safety.
Bolts are usually installed no more than 6 feet apart. The work involved is likely to be extensive
and may require that portions of the walls or floor be cut away temporarily.
Your contractor may be able to recommend an alternative anchoring method based on other
approved fasteners or connectors that can be installed with fewer changes to your house and
with less work.
If your house is built on cripple walls, you should consider bracing them after the sill plates are
bolted. For more information, refer to the separate earthquake protection fact sheet titled
Brace
Cripple Walls.
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3
E
STIMATED
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OST
Having a contractor bolt the sill plates to the foundation will cost about $50 to $75 per bolt, depending
on the type of foundation you have. For example, a house measuring 60 feet by 30 feet, will have a
perimeter of 180 feet and would therefore require a minimum of 30 bolts (if the bolts are placed no
more than 6 feet apart). So the cost for that house would be about $1,500 to $2,250.
O
THER
S
OURCES OF
I
NFORMATION
Seismic Retrofit Training for Building Contractors and Building Inspectors: Participant Handbook,
FEMA, 1995
Reducing the Risks of Nonstructural Earthquake Damage: A Practical Guide,
FEMA-74, 1994
Protecting Your Home and Business from Nonstructural Earthquake Damage,
FEMA, 1994
To obtain copies of these and other FEMA documents, call FEMA Publications at 1-800-480-2520. Information is
also available on the World Wide Web at
http//:www.fema.gov.

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