Earthquake Retrofitting

AVANT-GARDE

The United States Geological Survey says there is a 100% chance of a 5.4 or greater earthquake occurring in the Bay Area within the next 35 years.
An earthquake of this magnitude will put every home in the Bay Area at risk, and many do not have the proper reinforcement necessary in order to avoid damage.
For this reason, we offer a consultation in order to evaluate your home’s structural integrity.

Earthquakes are a part of our reality – there is no way to prevent one; however, you can prevent the occurrence of catastrophic damage to your home by having us perform a thorough seismic retrofit. Earthquake retrofitting is the modification of existing structures in order to make them more resistant to seismic activity in the event of an earthquake. One of our missions at Avant-Garde is to retrofit every home in the Bay Area in order to keep the community safe.

The force of an earthquake will find your home’s weakest point, which is why it is critical to create a continuous load path. A continuous load path incorporates the use of wood, metal connectors, fasteners, and shear walls in order to connect the components of the home. If your home is one-story, 50% of your home’s cripple walls will become shear walls; if your home is two-stories or more, 80%. A cripple wall is the wall between the first floor and the foundation and it is typically the weakest part of older homes. A shear wall is a structural system composed of braced plywood panels in order to counter the effects of lateral loads acting on a structure.

Our earthquake retrofitting designs incorporate solutions to prevent failures observed in other earthquakes around the world and exceed that of the International Building Code. The most common failure found in recent earthquakes has been the mudsill. The mudsill is the framing member that connects your home to your foundation. Builders typically use pressure treated 2×6 or 3×6 members for mudsills; however, these members are just too thin and have been known to split in earthquakes. In new construction, we use pressure treated 4×6 members for our mudsills, giving the extra thickness needed to prevent failure.

In a retrofit situation, unless the foundation is being replaced, replacing the mudsill just doesn’t make sense; therefore, we recommend adding 4x blocking on top of your existing mudsill in order to give it the strength it needs. Anchor bolts are then installed through the blocks, connecting them to your foundation. An anchor bolt is a 5/8″ threaded rod topped with a 3″ x 3″ bearing plate and nut in order to keep mudsill and blocking tightly connected to foundation. When the walls are over 4' in height, each end of your shear walls will include a hold down. A hold-down provides uplift resistance against overturning caused from lateral loads applied at the top of each shear wall. In situations where the cripple walls are not tall enough to provide a traditional 5/8″ anchor bolt, URFP10 bolts will be used instead. In this instance, structural screws will be used to connect the 4x blocking to the mudsill, and the URFP10 will connect the mudsill to the foundation.

We proudly use Simpson Strong-Tie. Simpson Strong-Tie is considered a leader in structural systems research, testing and innovation, and is one of the largest suppliers of structural building products in the world– The World’s “No Equal” Structural Connector Company.

The Association of Bay Area Governments is the regional planning agency for the entire San Francisco Bay region. ABAG’s Resilience Program supports recovery and mitigation research, planning and action for a resilient Bay Area. We support ABAG’s mission and encourage all Bay Area residents to enroll in their newsletter.

The California Residential Mitigation Program has established the Earthquake Brace + Bolt program in order to reduce retrofitting costs for homeowners. Using this program, you may qualify for up to $3,000 toward a seismic retrofit. We are proud to say that we are EBB qualified and our employees are FEMA trained.

Take the time now to contact us and let’s protect your home — and more importantly your family — together.