Your Commercial Real Estate Source in the San Francisco Bay Area
By Dean Andrews
For those transacting or financing real estate in San Francisco, there are several things to consider about the condition of your asset that are unique to the City by the Bay. These items should be identified and addressed with a thorough Seismic Risk Assessment/Probable Maximum Loss and Property Condition Assessment.
As with most earthquake prone areas, buildings in San Francisco should undergo a Seismic Risk Assessment or “Probable Maximum Loss” report to rate the building for seismic risk. It’s no secret that San Francisco is synonymous with earthquakes as the area is home to many known seismic fault lines. To make matters worse, much of the city sits on soil with a high liquefaction coefficient and when it starts shaking, the soil basically becomes like liquid and the buildings can actually sink or tilt. You will see steps from the sidewalk go down to the building entry door where the door was once at street level.
After the devastating damaged caused by the earthquakes of 1906 and 1989, the city has adopted some strict guidelines with respect to structural design of new buildings as well as strengthening older buildings, more specifically, unreinforced masonry buildings. Most brick buildings built prior to the early 1930s have no reinforcing steel. These are among the first to topple during an earthquake. The city now requires all unreinforced masonry buildings be retrofitted.
Since most of the city is on a hill and street parking is limited, many older buildings have parking garages at the first floor of the building, creating what is called a “soft story”. The garage door openings limit the amount of shear wall space available making these buildings vulnerable to collapse. Buildings such as these should be strengthened by installing rigid steel frames at the garage door openings. This retrofit might be recommended subsequent to a Probable Maximum Loss (PML) report.
One aspect unique to San Francisco is that many older buildings were constructed with a zero lot line. This means that they abut the adjacent buildings with no more than a few inches between them. During an earthquake, the buildings will start banging into each other introducing additional lateral forces. This is referred to as “pounding” and can be overlooked when considering the lateral stability of a structure.
The engineer inspecting the property should investigate the presence of these conditions to accurately analyze the structures ability to resist all lateral forces with minimal damage.
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