With the inevitable large earthquake on the horizon and the large stock of weak wood-framed buildings built before modern earthquake code changes in the late 70’s, San Francisco decided to be proactive about protecting its housing stock. The soft story ordinance requires owners of buildings with 5 or more units and 2 or more stories to retrofit/strengthen their weak buildings.
WHAT IS A SOFT STORY?
A soft story building is one that has an open facade (garage opening, windows, doors, etc…) on the ground floor, thus making the ground floors less stiff than the upper ones. These buildings are susceptible to large amounts of side-sway in an earthquake and are vulnerable to collapse.
WHAT’S THE WORK TO BE COMPLETED?
Most common soft story retrofits in SF will consist of installing some of the following seismic resisting elements:
- Bolting wood structure to foundation on all exterior walls
- Adding plywood shear walls on all basement or lower story walls
- Steel moment frame (see Simpson moment frame below as one option)
- Light gauge seismic hardware (clips, straps, ties, etc…)
- Reinforced or new foundation elements
What is required for each retrofit job is specific to each building and is based on a building’s weight, geometry, and existing construction.
SOFT STORY SCREENING FORM
This form, sent to every owner of buildings on the list, verifies whether buildings meet the criteria of the ordinance and categorizes the buildings into 4 different “ compliance tiers.” Each tier has a different deadline for completion of the work. Larger buildings with 15 or more units or ones that have more public zoning are deemed to be higher risk for loss of life in an earthquake, and are therefore required to be completed first. In contrast, soft story buildings that have ground floor commercial have been assigned to a later deadline to provide owners with more time to perform the seismic work.
The screening forms must all be submitted by September 15, 2014.
Link to Screening Form
OPTIONAL EVALUATION FORM AND STRUCTURAL WORK EXEMPTION
The ordinance will exempt structural work for retrofits completed within the last 15 years if they satisfy certain current code requirements. In order to accept these exemptions, the city will also need documentation of the previous retrofit work: plans, calculations, permit records, and anything else that may help show the extent of the seismic work and verify its completion.
In order to gain exemption from the soft story ordinance for such previously completed seismic work, owners may engage an engineer to fill out the optional evaluation form. An engineer may still need to perform calculations to show that the completed work meets the current code standards as required by the ordinance.
Link to Optional Evaluation Form
- Contact an engineer to meet you on-site and review the condition of the building. Have them fill out and submit the soft story screening form
- Have engineer develop a set of plans for the retrofit work
- Use plans to get bids for the seismic work and begin with construction
If you have any questions about the process or want to discuss moving forward with engineering plans for your soft story building, feel free to give me a call.