The only thing predictable about earthquakes is we know they'll continue to occur and impact communities around the world. While there is no way to prevent them from happening, societies can proactively prepare for earthquakes - from both a safety and financial standpoint - to ensure their lives and livelihood are protected. This preparation is even more important for people living in high risk earthquake areas such as California.
If you live in California and are a homeowner, you without a doubt want your home to be safe for you and your family in case an earthquake hits. That being said, many homes built pre-1979 in California might not be up to currently enforced building codes. These homes were built using un-plated foundation bolts that can corrode over time and weaken the connection to the home's foundation. This was evident in the recent Napa earthquake in 2014. If a moderate earthquake was to hit the area, it could dislodge these homes of their concrete foundation. There are three earthquake forces that can affect these homes:
Sliding - house slides off foundation
Racking - cripple walls buckle and collapse
Overturning - house lifts off foundation
So what can you do to protect yourself? One way to strengthen your home is called Seismic Retrofitting, or bolting your house to its foundation and bracing the walls. If you live in a home that has wood framing, built pre-1979 and is on a raised foundation, then you may want to think about what is called "The Brace and Bolt Retrofit" to keep your house on its foundation for any seismic activity.
How does this work?
Below are a few ways to keep your home safe.
Bolting: Foundation bolting is bolting (mechanical anchors) added to improve the connection between the wood framing of the house and its concrete foundation. These bolts are carefully planned and placed for strength through a piece of plywood that lies flat on top of the foundation, referred to as sill or mudsill into the concrete.
Bracing: Most houses have a short wood-framed crawl space under the house, less than four feet in height known as a cripple wall. When, the cripple wall is strengthened and braced it will keep it from collapsing during any type of seismic activity. Bracing is where they attach structural grade plywood tight to the wall framing (this is known as a shear wall). The plywood runs along the side walls of the house and will brace it in from the front to back direction. Plywood that runs along the front and back will brace the house from the side-to-side direction. Some homes may require additional hold-down brackets to anchor the shear wall.
Soft Story: There is also another circumstance called a soft story. These are living spaces in the house that are over large openings such as a garage door. These openings have little or no shear strength to withstand any seismic activity. They can be strengthened by installing structural grade plywood bracing against the wall next to and in-line with the openings. Another solution is engineered steel frames.
Some homeowners might think the cost to retrofit their home might be too expensive. The brace and bolt retrofit typically cost between $3,000 - $7,000 depending on the location and size of the house. This includes using certified contractors, material and work involved. Some insurance companies offer policy premium discounts to policy holders that retrofit their houses. There are also some government financial incentives for qualified homeowners to help pay up to $3,000 for the retrofit to a limited number of California zip codes. Money that you save from your premium over time, could offset the cost to retrofit your home.
A combination of the retrofit and insurance coverage can help mitigate costly repairs for a moderate to large seismic event - ultimately protecting your home, as well as your family.
If you have a home in California and want to know more about the Brace and Bolt program, visit: https://www.earthquakebracebolt.com
Category: Climate/natural disasters: Earthquakes
Location: California, United States