Recent earthquake probability studies indicate that much of this net worth may  soon be at a great risk.

Earthquakes from a potential 6.0 event on the Newport Inglewood fault alone could put upwards of one million older homes at risk, due to the fact that less than 12%  have proper retrofitting.

Engineers and seismologists agree that seismic retrofitting, when done properly, will significantly reduce potential damages from  a Big One.

The best thing you as a homeowner can do is get a better understanding of retrofit principles so that you can ask relevant questions and pick the contractor that will do the best job for you.

The concept of a seismic retrofit is not really rocket science: Bolt the house to the foundation, add plywood to brace the cripple walls, then use special hardware to connect those elements together.

The idea here is to transfer forces of the earthquake to the foundation. A building that's tied together and then attached firmly to its foundation is a lot less likely to collapse or slide off its foundation.

The concept is simple, but execution can be technical. A large number of contractors say they know how to install foundation bolts, shear walls and transfer hardware. But understanding exactly where to use them is quite another matter.

"The biggest problem to many contractors is a lack of knowledge of how seismic energy translates itself into a building. They will often nail plywood on to a cripple wall that will not see any of the lateral components of the earthquake, leaving a critical wall unprotected or improperly fastened. The owner thinks he's added a shear wall and, in reality, it may be effectively doing nothing."

A Glendale anesthesiologist thought he had gotten a correct retrofit surgery for his two story home. Much to his surprise all he really got was a bit of anesthetic.

It may not have been that his contractor was out to get him, but the workers did not have the specific knowledge needed to do adequate earthquake retrofit. In fact more than 70% of other contractor's work we are asked to inspect is a botched effort by well-meaning, but improperly trained contractors and/or their ignorant workforce. To make things worse, many building department inspectors have little energy or an adequate  idea of what they are supposed to be looking for.

Costs will vary widely

Procedures for simple homes are pretty well established. The Los Angeles “Specific Plan” is pretty well accepted throughout Southern California, with very few exceptions, the details are clear and can be handled by a competent contractor.

One of the most vulnerable buildings are the so-called "soft-story structures," or “HOGS”  habitable space over a garage.  Assuming the foundation is serviceable, retrofitting a soft-story building can cost as little as $6,000 or as much as $30,000 sometimes more..

Brick or stone foundations may need to be either replaced or sistered on the interior side. A sister foundation is a new reinforced concrete foundation attached on the inside face of the old foundation along with a new mud sill and foundation bolts added. It is more cost-efficient because it doesn't require that a new wall be built to support the house while the old brick or stone foundation is being demolished and hauled away.

Be warned of fraud, some contractors are marketing themselves as 'seismic retrofit' specialists and telling homeowners that they should pay for a variety of services that are very probably not needed. For example, the need to replace bolts due to 'rust', bracing of non-existent cripple walls, or adding hardware and bracing to the isolated piers in the central portions of the under-floor area.

Foundation work (replacement or sistering) would likely be  the most expensive part of a seismic retrofit. Some of those projects can cost $50,000 and, depending on the crawl space and how much access workers have, can easily swell to $80,000.

"Any new construction, such as an upper floor addition, must be engineered to current seismic requirements.

And, when will you need engineered details?

Contractors who are experienced in seismic retrofitting can take on most jobs, but when these situations present themselves, it is most probably best to first get engineering.

-- When your foundation is brick, stone, concrete block, or is weak.

-- When your home is very long and narrow, or has an unusually shape.

-- When your home is on a steep hill or split level construction.

-- When your home has a two-car or larger garage with habitable living space above it.

(800)-300-BOLT (2658) or  (626) 791-2300

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Seismic Safety - Ed Sylvis Construction
1410 North Lake Avenue
Pasadena, California 91104