What Does House Bolting / Earthquake Retrofitting Mean?

Your Southern California home in Los Angeles is located in a high-risk area. A safe home is one that can withstand earthquake shock forces and one that is built on a firm foundation.

Keeping you and your loved ones safe from earthquake harm becomes greatly improved when your home is securely fastened to its foundation and all of the home’s components are braced together.

Most residential homes are either built on a slab or raised foundations. The home’s weight is the primary reason that keeps the house from moving or sliding off its foundation. Foundation Bolting is the process of fastening the house to the foundation perimeter. Bolting your house is the best measure you can take to prevent damage inflicted by earthquakes, water damage and natural house settling

The term retrofitting refers to the modification of an existing structure (property) or device for the purpose of increased safety, efficiency or structural integrity.Retrofitting a home is a process that increases the resistance to earthquake damage and lowers the risk of injury and damage to your property. In short, earthquake retrofit significantly strengthens the foundation of your home and its endurance of it in case of seismic activity. 

Homeowners FREE Foundation Inspection For Earthquake Preparedness.

Call (323)418-2239

Earthquake Brace Bolt
foundation bolting

Foundation Bolting

cripple wall bracing

Cripple Wall Bracing

house bolting

Foundation Anchor Plates

Foundation Bolting / House Bolting:

If your house was built before 1950, it is indeed just sitting on your concrete foundation. IT IS NOT ATTACHED IN ANY WAY!

This means that in even in a small tremor, your house can go sliding off into your driveway. The Mudsill is the wood that rests directly on top of the foundation. Until the 1950’s builders did not bolt the Mudsill to the foundation, leaving it vulnerable to sliding during earthquake tremors.

earthquake retrofitting

Foundation bolting (House Bolting or Earthquake Retrofit) has been compared to a seat belt for your house. The up-and-down and side-to-side motion of an earthquake can shake an unbolted house off its foundation.During the 1994 Northridge earthquake, thousands of unbolted homes were damaged or destroyed. We can help you by preparing your home. Foundation bolting is easy, quick and inexpensive and provides greater protection against the forces of earthquakes.

Cripple Wall Bracing

The cripple walls are the section of your house that rest right above the Mudsill. They support the weight of the house and create a crawl space. If the cripple wall is covered on the exterior with only stucco or wood siding, it is not strong enough to resist earthquakes. You will need to strengthen your cripple wall to prevent serious damage to your home by bracing the cripple walls with plywood. Cripple walls that are not braced may collapse with the side-to-side swaying of the house during an earthquake, causing the house to fall. 

cripple wall

To secure the home, new lumber would be added as backing to create solid edges for the shear wall nailing. Expansion bolts would be placed, and the framing anchors would connect the rim joist to the top of the cripple wall. The cripple walls are now braced. Bracing the cripple walls by using structural-grade plywood is simple and provides greater resistance to earthquakes. Bolting your Mudsill to the foundation and adding plywood to the cripple walls are the two most cost-effective steps you can take to earthquake-safe your home in Los Angeles County.

On many homes, it is not possible to install foundation bolts because there is too little room between the top of the Mudsill and the floor of the house. This is because either there is no cripple wall or the cripple wall is extremely short. In these cases, special hardware known as “foundation anchor plates” is used to secure the house to the foundation.

wood blocking

Wood Blocking

In applications where the Mudsill is wider than the cripple wall studs, blocking will need to be installed on top of the Mudsill to provide a nailing surface for the sheathing. In order for sheathing to strengthen the cripple walls, it needs to be properly nailed on all four sides.The plywood is then nailed into the 2×4 blocks at the bottom of the plywood which have in turn bolted the house to the foundation. The point of concern when using the nailed blocking method is that the blocks can split which can make a seismic retrofit ineffective.

Earthquake Brace and Bolt Program ( EBB)

Earthquake Brace and Bolt is a grant program by the state of California and the California Earthquake Authority for homeowners who want to retrofit their properties against earthquakes.  The Earthquake Brace and Bolt  Program (EBB) was started because of the likelihood of a high-intensity earthquake striking California including Los Angeles anytime soon. The program gives homeowners up to $3000 of the total cost of the retrofit work done.

Homeowners must meet the following criteria :

  • Homeowners must own and live in the property being retrofitted
  • The house must be located in one of the ZIP codes designated by EBB
  • Each house can only register once
  • The retrofit may not receive any other grants from other programs
  • The house must pass a final inspection by a building inspector
Earthquake Brace and Bolt

Homeowners and contractors need to adhere to all of the listed terms of the Earthquake Brace and Bolt program and those that are not listed here too.

arrow_greenAfter a thorough assessment, one of our foundation repair experts will provide you with a free*, no-obligation quote.


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