Homeowner’s Guide to Seismic Retrofitting

The Homeowner’s Guide to Seismic Retrofitting is an unabridged version of the article, “Seismic Retrofitting of Cripple Walls,” written by Bay Area Retrofit for the April 2006 edition of the Journal of Light Construction, a national trade magazine. It is intended to help you determine whether your house needs new or additional seismic retrofitting, or has been retrofitted properly.

Homeowner’s Guide to Seismic Retrofitting

Seismic retrofitting a house to the foundation costs thousands of dollars and researching this topic is the best way to make sure your money well spent when it comes to retrofitting your house. House bolting is only one part of a seismic retrofit and here you will discover there are many other things that comprise a seismic retrofit.
In older houses, you will not find an attachment of the floor to the foundation. Making this attachment is the purpose of a seismic retrofit. Get best guide from Los Angeles earthquake retrofit


What Happens after an Earthquake?

Above the first floor, interior finishes on the walls and partitions such as plaster, though not designed to resist earthquakes, do in fact provide a lot of earthquake resistance. This part of the house above the crawl space does not need further bolting. The failures always occur in the crawl space under your floor. The house needs to be bolted to the foundation, and cripple walls need to be converted into plywood shear walls.

After an earthquake, wall and partition finishes may be cracked, doors and windows may be racked, and costly repairs may be required to restore livability to common standards. Damage always occurs, whether the house has been retrofitted or not. But damage above the floor is much less likely to result in a hazardous condition if the house was seismically retrofitted.

Most Bay Area homes were built before the building code required house bolting or had other earthquake resistant provisions. Un-retrofitted older homes with un-braced cripple walls need to be seismically retrofitted to avoid collapse in an earthquake. California does not have a seismic retrofit building code to guide cities and seismic retrofit contractors in the proper way to bolt and seismically retrofit your house. Nor is there special licensing for seismic retrofit contractors. Although your city may issue permits for seismic retrofit work and bolting houses, the state and your City has no code by which to evaluate the work. This puts the responsibility on you, the homeowner. If you take the time to understand the basic principles of seismic retrofitting, you can make sure your retrofit is done properly.

Most houses need to be seismically retrofitted in three ways:
1. The cripple walls of the house need to be braced with plywood.
2. The house needs to be bolted to the foundation.
3. The floor of the house needs to be attached to the braced cripple walls.
The following illustrations explain these important three steps. Without all three, your un-retrofitted house can fall off of its foundation.

The Homeowner’s Guide to Seismic Retrofitting is an unabridged version of the article, “Seismic Retrofitting of Cripple Walls,” written by Bay Area Retrofit for the April 2006 edition of the Journal of Light Construction, a national trade magazine. It is intended to help you determine whether your house needs new or additional seismic retrofitting, or has been retrofitted properly. Every house is different, though the earthquake engineering principles are always the same for every seismic retrofit.

House bolting is only one part of a seismic retrofit and here you will discover there are many other things that comprise a seismic retrofit.

California does not have a seismic retrofit building code to guide cities and seismic retrofit contractors in the proper way to bolt and seismically retrofit your house.

Leave a Reply

Your email address will not be published. Required fields are marked *