Earthquake Retrofitting; House Bolting and Cripple Wall Bracing

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As a homeowner, you should be aware of the unique nature of Residential Seismic Retrofitting.  It is a construction specialty.  This is a one-of-a kind business.  The work is difficult and arduous due to the tight working conditions under older homes and we perform comprehensive inspections to be sure our recommendations and cost estimates are thorough.  We go the extra mile and give you a written report compiled by our experts that you can rely on that accurately reflects your home’s seismic safety status. The contractors, inspectors and construction teams at Seismic Safety are specialists in residential Earthquake Retrofitting; House Bolting and Cripple Wall Bracing and have been since 1954.  It is our entire focus. 

Some people still believe in the myth that by leaving a foundation unbolted will allow the house to slip around a little and dissipate the energy from a small earthquake.  Not using house bolting in Southern California is like saying, “I don’t have brakes on my car because if you put them on too hard, you could bump your head”. 

Earthquake experts in seismic design and construction guidance tell us, and have proven, that a properly anchored floor foundation diagram uniformly distributes load, and actually strengthens the components during an earthquake.

Why you should Retrofit your home to protect it from further Earthquake damage

Retrofitting only has to work once to pay for itself.  Seismic Safety is a knowledgeable contractor who will make sure it does work, that one time.  Seismic Safety guarantees final inspection approval by your local jurisdiction.

What’s involved in a Seismic Safety Earthquake Retrofit or House Bolting Project?

This rendering shows you some of the prescriptive improvements involved in the type of work necessary to retrofit and bolt you home to protect it from Earthquake damage. The work involves attaching a house to its concrete foundation using anchor bolts and foundation plates, bracing of cripple walls and properly tying the floor system down with approved framing anchors.

What are the Cripple Walls?

One of the most common terms in the Seismic Retrofit and House Bolting process is known as Cripple Wall Bracing.   A cripple wall is a short stud wall that extends from the top of the perimeter foundation upward to support the floor joists.  The potential danger comes from the fact that though cripple walls are designed to bear weight from above, the lateral load caused by an earthquake can cause them to tip over and collapse like dominoes.  Un-reinforced cripple walls are a weak link for getting the earthquake loads from the lower floor to the foundation.
Plywood reinforcement on the inside faces of the cripple-wall studs can save a house from destruction in a future earthquake.  This is a relatively low cost fix; neglecting it is foolhardy. 

Not all homes have cripple walls, but that won’t stop opportunistic contractors from offering to brace them.  Cripple wall bracing is done by installing plywood sheets, called shear walls, which span the studs and help resist lateral stress.  Ask the Experts at Seismic Safety to inspect and evaluate your particular situation.