Does Your Home Need Earthquake Retrofitting in Los Angeles?

If built prior to the year 2000, than your home or building definitely needs earthquake retrofitting. The first, and most important step of retrofitting is to address the foundation. And when a foundation is retrofitted, it’s not a matter of the type of foundation, but rather the design flaws during the original construction.

In the case of early 20th century foundations; many homes and buildings were built with brick perimeter foundations and post/pier interior. And the majority of these, “Raised” foundations were never fortified with any type of steel or iron. The mortar over time deteriorates and quite often the bricks begin to fall away. We see this in 100% of early homes. The piers and posts that support the floor girders were placed on a rock or a brick platform laid directly on the soil. The posts are generally 3×4 inches with no connection to the girder other than a single nail. The perimeter framing was set directly on the brick perimeter footing with minimal bolting and zero lateral structural bracing. The namesake, “cripple wall” became synonymous with being the crippling design of a home or building’s foundation, as it was often the location of failure. Fortunately, seismic retrofitting will prevent this type of failure.

Cripple Wall Failure

When retrofitting these types of houses, quite often it requires building new foundation posts or piers and stem walls. It also involves adding sheer paneling on all cripple walls as well as bolting the framing to the new footings. It’s also suggested to install helical or push piers, connected to angle iron brackets to support loads where the foundation is settling due to expansive or eroded soils. These older homes are very prevalent from Pasadena all the way to Santa Monica, especially in the “high rent” districts of Fairfax, Hancock Park, and old Pasadena. Almost every home in South Central Los Angeles needs retrofitting and would benefit from California’s $3,000 grant funds as well as the 100% financing options through Foundation Technology.

Slab on grade foundations of the 40’s through the 90’s do not have the same cripple wall failure in design but most were not built to current standards. In earthquakes many of these homes slide off the foundation or collapse when the framing is buckled from the “sway” of the event. Retrofitting these homes require foundation bolting and sheer panel’s placed at strategic locations on all corners to eliminate the “rocking” and potential lateral collapse from a seismic event. Although seemingly more simple, the work is more intensive since the perimeter walls need to be opened to bolt the framing based on the engineers requirements, usually every 5-feet. Exterior siding needs to be removed to install plywood sheer panels and metal straps.

Soft Story Foundation Failure

Commercial and multifamily, (apartment complexes) built before 1980 are all susceptible to severe earthquake damage, especially the types with underground or beneath parking. These all need major retrofitting but also require a specific structural engineering plan. At Foundation Technology, we can do just about any of these with relative ease. We have engineering on staff and can offer comprehensive retrofitting plans along with 100% finance options to lighten the initial capital expense. These types of properties will be required to retrofit by ate 2015 in accordance with Mayor Garcetti’s safety proposal. The county assessor’s office can identify every property built prior to 1980 which means most of Los Angeles County will be required to retrofit.

The majority of commercial buildings in Southern California do not have the thorough bolting requirements of today. It’s also common in Los Angeles to see property that needs a complete roof/ceiling seismic retrofit given the susceptibility to collapse. In addition, all government facilities or structures built before 1980 are considered a viable retrofit candidate.

Hillside Stabilization

Hillside homes built any time before 2000 are prime candidates for retrofitting. At Foundation Technology, we can install hillside stabilization, (diagonally installed helical tie-backs and other stabilization products to help support hillside structures). Deep soil injection and polyurethane foam can also be used to stabilize and backfill hillside erosion voids. These methods also provide a flexible bed that would move in the event of an earthquake. There are about 200,000 hillside homes in the Los Angeles metropolitan region that could be affected by a seismic event similar to the 1994 earthquake in Northridge. Drive up any canyon road over to the city and look above you.

Seismic retrofitting or structural bracing is not limited to just habitable structures. It’s important to keep in mind that any structure will benefit from helical pier foundation or hillside bracing, or other retrofitting methods as determined by a structural engineer.