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Seismic retrofit is not rocket science, and the basic principles are easily understood. You can quickly learn all you need to know in order to make informed decisions regarding the retrofit of your home. Retrofit work is an investment, and taking a few moments to understand what it is will pay off in the end. For more detailed information, see our Retrofit Book page.
How much does a retrofit cost? The cost to retrofit a home depends on: the way the house was originally built, where it is relative to a fault, the height of the cripple walls, the number of stories, and many other factors.
Though costs can vary greatly, a seismic retrofit generally costs between 1% and 3% of a home's value. For many homeowners this one-time cost of a retrofit equals two to four years of earthquake insurance. And insurance won't prevent your house from becoming uninhabitable while a good retrofit will.
What is seismic retrofitting? During an earthquake the ground shakes violently. This back-and-forth motion can cause a building to slide and topples off its foundation. Invariably, this causes major structural damage and sometimes even total collapse. When this happens the home becomes uninhabitable. The goal of seismic retrofitting is to keep the house on its foundation and keep it habitable by applying earthquake engineering principles, specially designed hardware, and unique construction practices.
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 This house was not retrofitted properly and the homeowner is trying to save it before an aftershock hits.
How much does retrofitting help? In 1994 after the Northridge Earthquake president Bill Clinton visited a neighborhood where most of the homes had suffered severe damage. He also visited one house that had sustained very little damage because it had been retrofitted. After that, he directed FEMA to help pay for retrofits for homes built in Los Angeles. Another demonstration of its effectiveness occurred when two identical houses, one retrofitted and the other not, were subject to intense shaking in the 1992 Loma Prieta Earthquake. For more info,read a True Story
Studies by the Association of Bay Area Governments show that a properly retrofitted home is almost one thousand percent (1000%) more resistant to earthquake damage than one that is not retrofitted.
Since earthquakes and the forces generated by them are unpredictable, seismic retrofitting cannot guarantee a house will receive no damage at all. Cracks in plaster, doors that don't open and close smoothly, and chimney falling down should be expected no matter how well the house has been retrofitted.
Do newer homes need reinforcement? Modern building codes have been written so that newer homes usually rarely need to be seismically reinforced assuming the contractor understood the importance of following this part of the building code. We have rarely seen this because following this part of the building code increases the cost of construction and/or the contractor did not know how to implement the seismic provisions of the building code. This is especially true with plywood nailing, the most crucial part of making a home earthquake resistance. Special hardware has been developed to add greater strength to newer homes and compensate for possible builder's oversights. Usually retrofits of newer homes are simple and inexpensive.
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What if I have an older home? Older houses are especially susceptible to earthquake damage because they were built before homes were required by law to be earthquake-resistant. They are therefore prime candidates for retrofitting. Most of them have cripple walls, the most serious structural weakness a house can have.
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Do I need a contractor or an engineer? As in other fields, contractors and engineers tend to specialize, so if you choose to work with an engineer or contractor, be sure it is one with special training in retrofit design. There is no point in asking to see his retrofit contractor licensing because special licensing is not required for retrofit contractors. Pick a contractor who has had special training in retrofit engineering principles. If he has this training, can also design your retrofit. These engineer- trained contractors, though hard to find, are usually the best choice. Not only do they understand the design principles, but they also understand the most practical ways to achieve maximum protection. In almost every case, an engineer-trained contractor will design a retrofit equal to that of an engineer but at a much more affordable price, not to mention the fact can pay an engineer $4,000 and up for a design you may not be able to afford.
Howard Cook of Bay Area Retrofit is an engineer-trained contractor. He traveled to Los Angeles in 1994 to see how homes were damaged and how this damage could be prevented in the future. At the same time he took the FEMA course "Principles of Seismic Retrofitting for Engineers , Contractors, and Building Officials," offered to contractors in Southern California on five different occasions.
Howard has also taken advanced instruction in seismic retrofitting principles from the leading structural engineers in this field and regularly consults with structural and seismic engineers as needed to make sure he provides his clients with the most cost-effective retrofits possible.
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How can I know whom to choose? Seismic retrofit technology is continually evolving, and a retrofit contractor needs to understand and apply the most current seismic retrofit research. Customer references can tell you whether he was on time, cleaned up after the job, etc. but cannot tell you if the contractor knows what he is doing. If you are doing a retrofit that involves shear walls, make sure he has read the book "Shear Walls, an Illustrated Guide", written by structural engineer Thor Matteson. Otherwise, the only way you can determine if your retrofit professional will retrofit your house properly, is by educating yourself. Then make sure the contractor explains exactly what he is going to do any why. If he cannot do this, he himself probably does not know what he is doing. This may require that you crawl under your house with him but it is the only way you can know if you are getting what you pay for.
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