Should you be considering a seismic retrofit in San Francisco?
Seismic retrofitting involves strengthening a structure to make it more resistant to earthquake shaking and damage. In many cases, the retrofitting process itself strengthens an older home by bolting the house to its foundation with anchor bolts, or with bracing and bolting. There are more than one million of these types of vulnerable older homes in high hazard earthquake areas across California, and many of those homes are in and around San Francisco. Many of these older homes were built before modern building codes were in place.
A recent study by the Pacific Earthquake Engineering Research (PEER) Center estimates that the owners of retrofitted houses can save between $10,000 and $200,000 in repair costs resulting from a major earthquake by bolting, or bracing and bolting, their homes with a seismic retrofit.
This research helps demonstrate that seismic retrofits work, and that earthquake retrofitting is worth it when you compare the potential cost of repairing a damaged home. Thorough research and analysis suggests that spending a smaller amount of money to help reduce damage and help give your house earthquake resistance may be more beneficial than facing a much larger repair bill after an earthquake.
What are the benefits of getting a retrofit in the San Francisco Bay Area?
Strengthening your house with a seismic retrofit in San Francisco is a good way to lessen the potential for costly earthquake damage, saving you what could be tens to hundreds of thousands of dollars in repair costs. It can help provide peace of mind, knowing that you have helped your family better withstand an earthquake by strengthening where you live.
These two side by side houses, shown after the magnitude 6.0 2014 American Canyon (South Napa) earthquake, illustrate the benefit of a seismic retrofit—as one had been strengthened and one had not.
How much does a retrofit cost in San Francisco?
If you are curious how much an earthquake retrofit costs in San Francisco, the range to retrofit a home on a raised foundation is usually between $3,000 and $7,000. Older houses with steps up to the first floor are on a raised foundation. This means they have an area underneath the first floor, which is referred to as a crawl space. These types of houses can shift off their foundations from shaking. They often can be strengthened by bolting the house to its foundation.
Larger homes, those built on hillsides and those with basements and rooms over garages will typically cost more to retrofit.
Importantly, homeowners can remain inside their dwelling as, in most cases, workers are able to do the retrofitting work without entering the residence. Compared to the potential cost of repairing an earthquake damaged home, spending a smaller amount of money to help prevent damage can help avoid a much bigger repair bill after an earthquake.
Does San Francisco offer any retrofit grant programs?
You might be wondering, are there seismic retrofit financing programs in San Francisco? There is a grant program available to eligible San Francisco area residents to help with the costs of a seismic retrofit in San Francisco. The California Residential Mitigation Program (CRMP) Earthquake Brace + Bolt (EBB) program offers grants to eligible Californians in higher-risk ZIP Codes.
Earthquake Brace + Bolt (EBB)
EBB is an incentive program that offers seismic retrofit grants of up to $3,000 to qualified homeowners with eligible houses in a select number of higher-earthquake-risk ZIP Codes.
ZIP Codes chosen for EBB retrofit program participation follow these two criteria:
- Earthquake Hazard: Hazard was identified using the United States Geological Survey (USGS) earthquake hazard map for California.
- Earthquake Vulnerability: Vulnerability was represented by identifying the percentage of pre-1940 houses in ZIP Codes in California (U.S. Census Data). Older houses are more likely to require earthquake bracing and bolting.
EBB may include other ZIP Codes in a city to allow for efficiency for contractors and building departments, thereby making more homeowners eligible for a grant.
Over time, EBB hopes to include more high hazard areas in California with additional funding from a variety of sources.
You may be eligible for an EBB grant if your house:
- Is owner-occupied and is in one of the EBB ZIP Codes.
- Is built before 1980 (but qualifying houses are more prevalent before 1940).
- Has a raised continuous perimeter concrete foundation.
- Sits on level ground or a low slope.
- Is of wood-framed construction.
San Francisco’s Seismic Retrofit Financing
Strengthening your home to make it more resistant against earthquake damage and loss is important. In addition to the program described above, there are a number of other potential funding sources available.
Learn about other types of financial assistance to help you retrofit your home to make it stronger against earthquake damage.
How to get a retrofit
When it comes to San Francisco retrofit requirements, once you have identified your house type and its vulnerabilities and you determine the type of retrofit that is needed, it is time for you to make a plan to carry out the retrofit. This includes hiring a contractor (or considering doing the work yourself), deciding how you will pay for the retrofit, and scheduling out the timeline for completion.
Earthquake retrofit contractors in San Francisco
It’s always best to get bids from several contractors before you make your final selection. The California State License Board (CSLB) also recommends obtaining more than one bid and makes available a San Francisco seismic retrofit list of contractors.
You can check out the list of contractors, who have received training and are experienced on how to do a brace and bolt retrofit.
Keep in mind that if your home requires an engineered retrofit, you or your contractor will need to hire a licensed structural or civil engineer to advise on your retrofit efforts. EBB has a Licensed Design Professional Directory to help you with your search.
What are the structural risks from an earthquake for each type of house foundation?
Because of the San Francisco Bay area’s housing diversity when it comes to the different ways its homes are built, these different types of homes pose their own risks and may require their own type of retrofitting to strengthen their ability to withstand the devastating force of a major earthquake.
Raised Foundation
Earthquake retrofitting in Northern California is important to help improve the resilience of San Francisco and the greater Bay Area. Property owners of wood frame buildings can complete a brace + bolt retrofit in order for it to be seismically strengthened. This type of seismic work only takes a few days and may cost less than you’d think.
A house with a raised foundation has an area underneath the first floor, which is referred to as a crawl space. Industry professionals use the term “cripple wall” to define crawl space walls. These older homes with steps up to the first floor can shift off their foundations from shaking. They can be strengthened by bolting or bracing and bolting the house to its foundation.
Here is an example of a house with this type of foundation—you can find more information on this risk at the Raised Foundation House Retrofit page.
Post and Pier House
A post and pier house is a type of raised foundation home, in that there is an area created underneath the dwelling floor.
You can find more information on this risk and what you can do to minimize it at the Post & Pier House Retrofit page.
Hillside House
These houses have certain, inherent structural elements that can make them vulnerable when earthquakes occur. They are built on hillsides or sleep slopes and often are set on tall, narrow posts or columns, with or without diagonal bracing.
Hillside houses can be at risk when it comes to strong shaking and may need to be strengthened by being properly retrofitted to withstand earthquakes.
You can find more information on this risk at the Hillside House Retrofit page.
Houses with a Living Space over a Garage
Houses with one or more floors of living space over an attached garage are vulnerable to shaking. Their vulnerability to earthquakes comes from a living space being atop the garage beneath, which lacks structural soundness. The garage area of these homes also may have walls and doors that are not braced to resist earthquake motion.
Soft story buildings and residences like these need a special type of soft story retrofit. Retrofitting the garage space can strengthen it—and make the existing building, and these types of homes, more resistant to earthquake damage.
Here is an example of a house with this type of foundation—you can find more information on this risk on the Living Space Over Garage House Retrofit page.
Mobilehomes and Manufactured Homes
Many mobilehomes and manufactured homes are built on support systems, such as steel jacks or masonry piers, to help them stay in place during normal living conditions. But, these were designed just for gravity loads—they are not typically not built to withstand earthquake shaking.
These types of homes need an Earthquake Resistant Bracing System (ERBS) to be installed to help them resist the damage that earthquake shaking can cause.
Learn more about this type of risk on our Mobilehome and Manufactured House Retrofit page.
What is your earthquake risk in the San Francisco Bay Area?
In their most recent report, the United States Geological Survey (USGS) predicted a 72 percent chance of one or more magnitude 6.7 or greater earthquakes striking the San Francisco Bay Area in the next 30 years, based on a 30-year period, beginning in 2014.
With a nearly 3 out of 4 chance of a damaging earthquake striking the area in the near future, it is important that residents of the region do everything possible to prepare their homes and themselves. In the San Francisco Bay Area, the USGS names the prime earthquake culprits as the San Andreas, Hayward and Calaveras faults.
A hypothetical earthquake scenario by the USGS called the HayWired Scenario estimates that millions of people in the San Francisco Bay Area region could be impacted by a 7.0 magnitude earthquake and its aftershocks. Under the HayWired scenario, the epicenter and mainshock would occur on the Hayward Fault beneath Oakland and could lead to the strong shaking of one million homes, could trigger widespread fires, and could lead to the displacement of up to 152,000 households and 411,000 people.
Loma Prieta Earthquake October 1989 (World Series Earthquake)
The last major earthquake to strike the San Francisco Bay Area was the Loma Prieta quake in October 1989. The magnitude 6.9 shaker was centered in Santa Cruz County on a section of the San Andreas Fault System and was named for the nearby Loma Prieta Peak in the Santa Cruz Mountains.
Damage Caused by the 1989 Loma Prieta Earthquake
The Loma Prieta quake was responsible for 63 deaths, more than 3,700 injuries and more than $5.6 billion in total damage. It also is remembered for its interruption of the 1989 Major League Baseball World Series, which, ironically, featured Bay Area rivals, the San Francisco Giants and the Oakland Athletics. For that reason, it is often referred to as the “World Series Earthquake”.
Here is an example of a house that was damaged by the Loma Prieta earthquake.
How to protect your home from a quake in the San Fransisco Bay Area
Even though it is impossible to accurately predict when an earthquake will occur, you can still take measures to reduce damage and improve the chances of staying safe by preparing in advance for earthquakes. The ways in which you can protect your home and your family in the event of a major earthquake (in addition to finding out if your home needs a seismic retrofit in San Francisco) include:
- Create an earthquake safety plan for you and loved ones, including pets.
- Know your risk for earthquakes in your area and what you must do to stay safe.
- Make or purchase earthquake safety kits.
- Identify and fix potential earthquake hazards in your home.
- Secure fixtures, furniture, appliances and other items inside your home.
- Visit the Seven Essential Earthquake Safety Steps page for more safety, protection and emergency preparedness tips.
Determine your structural risks
If you live in the San Francisco Bay Area and your raised foundation older house was built before 1980, earthquake experts say your dwelling is especially vulnerable to damage from earthquake shaking because it was built before seismic building codes were put in place. According to U.S. Census data, 81 percent of the housing units in San Francisco County fall into that category of being built before 1980 and could be in need of an earthquake retrofit in San Francisco. The frames of hundreds of thousands of these type homes are not bolted to their foundation. And without adequate bracing and bolting, these houses can slide or topple off their foundation during an earthquake.
While raised foundation older homes are prevalent in San Francisco, there are homes in the area with other foundation types that may be in need of retrofitting. Those homes include “post and pier” houses, hillside houses and houses with living spaces over garages. You can learn more about these homes, their foundations and how to determine whether they need to be retrofitted at our Strengthen Your House page.
Consider a seismic retrofit
As discussed in previous blogs, strengthening your house with a seismic retrofit in San Francisco is a good way to help prevent costly earthquake damage. It can help provide peace of mind, knowing that you have helped your home and your family better withstand an earthquake.
The retrofitting process itself can be straightforward and often not as intrusive as homeowners might think. Depending on the type of retrofit needed, the work usually can be done in a few days and homeowners can remain inside their dwelling, as in almost all cases workers do the retrofitting without entering the residence. The older your house, the greater the odds it may need to be seismically retrofitted to have a better chance to withstand earthquake damage. For more information on the importance of retrofitting different home types, visit our Strengthen Your House page.
Strengthen Your Home
For many San Francisco Bay Area homeowners, the value of their property and the equity they have in it represent the lion’s share of their savings and retirement nest egg. An earthquake retrofit in San Francisco can significantly reduce the chances of an older home falling or sliding completely off its foundation—perhaps resulting in a total loss, even in a moderate earthquake.
The primary goals of retrofitting are to:
- Allow you and your family to shelter in place.
- Protect against catastrophic financial loss.
- Help you and your family survive when a major earthquake occurs.
Living in the San Francisco Bay Area, it is not a matter of if, but when a major earthquake will occur. You can better protect and prepare yourself and your family before the next big one strikes by investing in an earthquake retrofit. Provide that protection by taking the path of most resilience by strengthening your home against earthquake damage today. For more information on the importance of retrofitting older homes, visit our Strengthen Your House page.