Feature
by Tim Carrico
San Francisco’s likelihood of having a major earthquake is on par with New Orleans’s likelihood of having a catastrophic hurricane. In other words: 100%. After the 1989 Loma Prieta “event,” San Francisco passed an ordinance to retrofit unreinforced masonry buildings. These brick buildings are considered to be the most likely to catastrophically fail in a major earthquake and injure or kill both the occupants and pedestrians on the sidewalks.
The vast majority of the brick buildings have now been retrofitted. City officials and interested parties then began discussing, what, if anything, should be done next to protect our buildings from damage and our citizens from injury, as well as what needs to be done now to plan for the post-earthquake rebuilding that will be required.
Several years ago, San Francisco’s Department of Building Inspection assembled a group of interested people—structural engineers, soil engineers, earthquake specialists, city officials, building owners and other related experts—to begin looking into what the anticipated damage would be under different earthquake scenarios and what pre- and post-earthquake measures should be adopted to deal with the risks. The committee was named the Community Action Plan for Seismic Safety. CAPSS hired a team of specialists to begin assembling data for it to use in its analysis.
The CAPSS program was disbanded several years ago due to a lack of funding and interest on the part of the city. At the point it was disbanded, the study of the damage potential throughout the city was just about completed and a preliminary report was written.
Recently, there has been a renewed interest in restarting the CAPSS process. If it does get going again, the group will probably issue a final version of its damage-assessment studies. Then the final phase of its process would begin. This phase would study the options and the impacts of additional pre-earthquake requirements for retrofitting existing buildings and recommend what types and levels of retrofits should be required on buildings that would likely be damaged in an earthquake.
Of most interest to existing property owners is the question of what, if any, new requirements may be imposed that would require additional investment to seismically upgrade their buildings. From talking to several key people involved in the process, it doesn’t sound like any major new upgrade requirements are imminent. The primary structural risks in residential buildings are for “soft-story” structures, typically wood-frame buildings and nonductile concrete buildings.
A soft-story building is one in which the ground floor has a lot of open space with few cross walls. Examples are corner apartment buildings with lots of open garage parking on the ground floor and commercial buildings with ground-floor retail uses and apartments above. In 1989, the Marina district saw several corner apartment buildings either fall into the street or come close to it.
The cost of strengthening the ground floor of a wood-frame soft-story apartment building is not exorbitant, since the walls are generally unfinished and accessible to workers. Mixed-use buildings, however, may be more costly because the work would disrupt an operating business and be hindered by finished walls, shelving, inventory, plumbing and more. In addition, doing this type of work would probably trigger handicap-accessibility requirements, which can add substantially to the cost in some instances.
Nonductile concrete buildings, on the other hand, pose a much more difficult and costly problem to address. Most, if not all, concrete buildings constructed prior to 1970, are of this design. This is basically a matter of how the steel-reinforcement components (or rebar) inside the concrete are connected together. Strengthening these buildings will apparently require digging into the walls and exposing the columns supporting the building and doing some messy, heavy-duty work to reinforce them. Remember those steel girdles that were on many of the columns supporting elevated freeways in the years after the 1989 earthquake? That was a temporary measure to address this type of problem.
The Gulf Coast hurricanes do not seem to have generated any groundswell, so to speak, of interest in accelerating our earthquake preparedness. Apparently pre-earthquake requirements for frame buildings might be limited to soft-story commercial and/or mixed-use buildings, and maybe just those on corners. A step up from including these types of buildings would be to add corner wood-frame apartment buildings.
The nonductile concrete-building problem doesn’t really seem to be on the table for much discussion because the solutions are so costly and politically challenging. Imagine trying to get 50 condominium owners to agree to spend what might be a few million dollars to address a problem that might never materialize for that building. Multiply that by hundreds of buildings, owners and tenants, and it’s definitely a shaky proposition.
In the long term a program may be proposed, but its scope will probably be limited to the most serious risks. In the meantime, if you want to proactively improve the earthquake resistance of your property, call a structural engineer. Improvements to the ground floors of many buildings can provide a large increase in seismic strengthening for the amount of money spent.
The opinions expressed in this article are those of the author and do not necessarily reflect the viewpoint of the SFAA or the San Francisco Apartment Magazine. Tim Carrico is past president of SFAA and owns TCO, a real-estate brokerage specializing in residential and investment property. He can be reached at 621-1600 x 200 or at tim@tco-sf.com. Copyright © 2006 by the San Francisco Apartment Magazine. All rights reserved.