BOLT SILL PLATES TO FOUNDATION
Protecting Your Property from Earthquakes
FEMA
April 2008

As shown in the figure, the sill plate of a structure rests directly 
on top of the foundation. (This figure shows the sill plate for a 
structure 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 slide with respect to the foundation. When this 
occurs, there is a greater potential for severe damage 
as well as injury to you and others. 

One way to increase the stability of your property 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 structure built on a 
basement or slab-on-grade foundation or on another type of crawl 
space foundation. 

BENEFITS OF UTILIZING THIS MITIGATION STRATEGY

* Helps to prevent a structure from shifting, which can result in 
severe damage

* Helps to prevent injuries to occupants

TIPS 

Keep these points in mind when you have the sill plates bolted to 
the foundation: 

* Modifications to the foundation 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. 

* Anchor 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 property and less work. 

* If your property 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.” 

ESTIMATED COST 

Having a contractor bolt the sill plates to the foundation will cost 
approximately $50 to $75 per bolt, depending on the type of 
foundation you have. For example, a structure measuring 60 feet by 
30 feet would 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 structure would be about $1,500 
to $2,250. 

OTHER SOURCES OF INFORMATION 

Brace Cripple Walls Fact Sheet, FEMA, April 2008, 
http://www.fema.gov/plan/prevent/howto/index.shtm.

FEMA 74, Reducing the Risks of Nonstructural Earthquake Damage: A 
Practical Guide, Third Edition, September 1994, 
http://www.fema.gov/library/viewRecord.do?id=1574. 

FEMA 232, Homebuilders’ Guide to Earthquake-Resistant Design and 
Construction, June 2006, 
http://www.fema.gov/library/viewRecord.do?id=2103.

To obtain copies of FEMA documents, call the FEMA Publications 
Warehouse at 1-800-480-2520 or visit FEMA’s Library online at 
http//:www.fema.gov/library.