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Earthquake Retrofitting For Multi-Family Apartments

Earthquake Retrofitting For Multi-Family Apartments

According to the United States Geological Survey, the probability of a 6.7 or larger earthquake occurring sometime in the next 30 years in California is 99%.  With the probability that high, it’s not a matter of “if” there will be an earthquake, but rather “when” will it happen.  We know that the “BIG ONE” will occur; the issue really is about whether or not we are prepared.  Thankfully, there is still time to plan and prepare for such a major event.

Many homeowners and families prepare for earthquakes by creating an emergency response plan, purchasing earthquake kits, first aid kits, and so on.  These are all great ideas for individuals and families.  In the business world, planning for strong seismic activity is often more complicated.  Individuals or investors that own commercial real estate need to prepare the same items as individuals, plus they need to make additional preparations for their tenants and real estate.  This is especially important in multi-family dwellings, such as apartment buildings, where entire families occupy the units.

Following the 1994 Northridge Earthquake, multi-family dwellings of wood framed construction, particularly those with “soft story” construction or “tuck under” parking, sustained heavy structural damage.  In the aftermath, more than 2,700 multifamily dwellings (30,000 living units) had to be vacated or had significant structural damage from that one powerful earthquake..

Because of the lessons learned from the Northridge Earthquake, builders and property owners are much more aware of the built-in seismic risk to multi-family dwellings with soft story construction or tuck under parking.  Building codes have changed since then, therefore, it is in the best interest of all parties to have a thorough earthquake retrofit evaluation on this type of building structure.  This is especially true if the building is more than ten years old.  Investors, insurance companies, banks, and the government are all interested in having buildings strong, secure and ready to handle the impact of any seismic activity.

Instead of costly repairs performed after a major earthquake, it is much more cost effective and efficient to proactively retrofit a commercial property.  There are a variety of ways to earthquake retrofit a building with soft-story construction.  The most cost effective method to strengthen the diaphragm and shear walls is to sheath them with structural grade plywood nailed to the existing wood framing, thus improving the lateral force resisting system. Sometimes however, that is not enough; in fact, there are times when a steel moment frame with concrete footing is needed to improve the lateral resisting system.

It is important to discuss earthquake retrofitting with a licensed structural engineer and a licensed contractor in order to get a detailed a summary of the retrofit scope and a rough cost estimate.  The unique characteristics of the building, as well as its location, age, condition of construction, parking needs, and local building code requirements will dictate the type of mitigation measures needed to complete an earthquake retrofit effectively.

As a property owner or manager, you have the responsibility to promote the safety and security of your commercial property, especially for the tenants, machinery and inventory.  The professional team at Saunders Commercial Seismic Retrofit can provide a comprehensive and multi-faceted evaluation of your building.  In addition, Saunders will provide a retrofit insurance quote based on present and after-retrofitting values so you can easily calculate your Return on Investment.  If you have questions about earthquake preparedness or building structure safety, call Saunders Commercial Seismic Retrofit today!

Southern California Office

(949) 646-0034




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