San Francisco Soft Story Seismic Retrofit Ordinance

June 30, 2015

The Mandatory Soft Story Retrofit Ordinance 66-13 is a mandatory seismic retrofit program requiring evaluation and retrofit of multi-unit, wood-frame structures with five or more residential units, two or more stories over a "soft" or "weak" story, that were constructed before 1978. All buildings located in the City of San Francisco that fit these criteria are subject to this ordinance.

The ordinance required owners of soft story buildings to have their buildings screened in order to determine whether they are within the program.  The deadline for submitting the screening form was 15 September 2014.  All owners who have not completed this form are considered to be in violation of this program and will be issued an "Earthquake Warning" placard noticing the building's owner, tenants, and general public of the risk posed by the building.

Buildings that are included in the program are separated into four tiers depending on the building occupancy group and whether the building is located in a mapped liquefaction zone.  The deadlines for submitting plans for seismic retrofit as well as for completion of the retrofit are summarized in the following table:







SGH engineers can help building owners and property managers assess their buildings and prepare plans for the seismic retrofit. 

SGH has intimate knowledge of the requirements and allowable engineering procedures in the Soft Story Ordinance.  We have been active in developing and modifying the Administrative Bulletins that contain the provisions that are used for the retrofits.  We have a large staff of local licensed structural engineers who are knowledgeable in the performance of these types of buildings through studying their performance in the 1989 Loma Prieta and 1994 Northridge earthquakes, and who have published papers on the topic. 

Building owners and property managers turn to SGH when they need thoughtful and expert engineering guidance. We have evaluated and retrofitted many buildings with seismic deficiencies, including soft, weak and open fronts. Our numerous clients value the high standards we set for design efficiency, constructability, and long-term durability.

If a soft story building requires seismic upgrades, SGH can help.  

We work on projects in a variety of roles, including verifying previously completed San Francisco soft story ordinance screening forms, determining whether previous retrofits satisfy the requirements of the ordinance, or acting as the engineer-of-record for the retrofit.     

The general steps involved in a seismic strengthening program vary from project to project but are generally as follows:

 



1.       Assumption:  You own one or more buildings, the required form was completed by a licensed professional, and you are in the program. 

 



2.       Hire an experienced and qualified structural engineer (theoretically this could also be an experienced architect, but we will assume a structural engineer for sake of discussion).  The kind of experience you are looking for is experience seismically retrofitting existing buildings.   They should also be familiar with the Ordinance and the two associated Administrative Bulletins.  The Administrative Bulletins are updated to reflect input from the Structural Engineers Association of Northern California Existing Building Committee (SEAONC EBC), engineers and SFDBI as work on buildings proceeds. 

The structural engineer you select could be the same engineer that filled out the screening form or it could be a different one.  We have encountered some completed forms that were filled out improperly so if you are hiring a different structural engineer, the first question you should ask the new structural engineer is if it is appropriate that you are in the program.

Things the structural engineer will consider when estimating their fee: 

  
 

  • Size of the building
  • Availability of drawings
  • Irregular geometry (e.g., hillside or lightwells),
  • Type of foundation (brick foundations are more challenging)
  • Evaluation approach

Meet with the structural engineer and discuss your project before he/she begins work.

  • Discuss your performance goal - just meet minimum ordinance requirements or do you want more or at least want to consider more where it is cost-effective to do so?
  • Share information you have about previous remodels, repairs, or possible deterioration (e.g., roof leaks).
  • Agree on logistics of site access for the structural engineer to do the evaluation. Generally the structural engineer will need to walk through entire ground and second floor, with more time spent on the ground floor.
  • Decide whether to perform destructive exploration to identify conditions (such as presence, size and spacing of anchor bolts in existing walls) during the evaluation phase  or make assumptions that are confirmed during construction.
  • Discuss limitations of the retrofit - e.g. can some of the garage door openings be closed or is it required that design maintain all openings? Can the openings be made smaller or do they need to remain the same size?  Generally maintaining openings requires using moment frames which are more expensive than shear walls.
  • Will the contractor have full access to the ground floor during construction or does work have to be phased to maintain some parking during construction? Phased construction will generally be more expensive.
  • Identify any concerns that might require another design professional
    • Architect (e.g., code compliance to satisfy disability requirements - more likely if commercial space below)
    • Mechanical or electrical engineer (relocation of utilities) 

3. Obtain existing drawings.

  • If owner does not have existing drawings, visit San Francisco's Department of Building Inspection's (SFDBI's) record management division.  The structural engineer can perform this task but the owner should expect to be a small fee for this task if it is not included in the structural engineer’s proposal.  An advantage to having the structural engineer do this is that they can better judge what information will be useful in some cases.   Reproduction of records can be done for a fee depending on the number of items to be copied, so if the owner self performs this this task he/she needs to make decisions that do involve copying too much and yet not missing valuable information. 
    • If not available, the structural engineer will need a more extensive site visit to develop drawings by taking measurements.  This will also require additional fee.  
    • If available, the structural engineer will need to verify the drawings are accurate through a site visit.

4. The structural engineer performs a  site visit

  • The owner can hire a contractor to open wall finishes (the structural engineer may be willing to do this if it's not necessary to close them back up) to verify critical information or the structural engineer can make assumptions and verify them during construction.
    • Presence of brick foundations
    • Wall connections to framing above
    • Wall connections to foundations (anchor bolts, etc.)
  • The structural engineer needs to pay attention to things that will affect possible retrofits
    • Do garage door openings have associated garage doors.
    • Narrow piers between door openings that preclude use of moment frames.
    • Cantilevered floors could require strengthening of second floor diaphragm  that could need waterproofing,
  • Depending on the structural engineer’s observations during the site visit, it may be appropriate for the owner to meet and discuss findings of their site visit if the owner does not accompany the structural engineer on the visit.

5. The structural engineer evaluates existing material strengths

  • The engineer can assume default material strengths if no drawings are available.
  • If material strengths in some area of the building are critical, or if a material appears to be suspiciously weak (e.g., crumbling concrete foundation) or deteriorated (e.g., water damage), it may be appropriate to do material testing.
    • Assumptions can be made and this can be done during construction by the special inspector/testing lab

6.  For sites with apparent poor soils based on publically available geotechnical maps (http://www.sfgsa.org/modules/showdocument.aspx?documentid=10438), the owner may need to hire a geotechnical engineer to determine if the soil is indeed poor and if necessary provide mitigation recommendations.

  • Publically available geotechnical maps tend to be conservative (i.e., they may indicate a site is in a zone of liquefaction when in fact a geotechnical engineer may be able to do a site-specific study and prove otherwise.
    • In order to provide site-specific information a geotechnical engineer will need to take one or more borings, which could cost up to $10,000 for a single boring depending on accessibility.
  • In typical soils areas, the structural engineer can usually use conservative code soil bearing values without much effect on the cost of the retrofit.
    • If you hire a geotechnical engineer, they can provide soil capacities for new foundations.
    • In order to provide these capacities, they will probably need to take one or more borings, which could cost up to $10,000 for a single boring depending on accessibility.  
  • Typically, the owner hires the geotechnical engineer. Structural engineers can usually suggest geotechnical engineers qualified to do the geotechnical investigation.

7. The structural engineer performs the evaluation - typically this means either hand calculations or a computer analysis.

  • If a building is found to meet ordinance requirement as-is the structural engineer will fill out the "Optional Evaluation Form," along with documentation (calculations, field investigation report, etc.) and submit it to the City.
    • This is unlikely unless the building was previously retrofitted or if the screening form was completed incorrectly. But it can happen and generally the structural engineer will suspect it before he/she begins the analysis and will provide a proposal with separate phases for evaluation and design of a retrofit.

8. Develop retrofit scheme(s)

  • Generally the owner should ask the structural engineer to show the conceptual scheme(s) for review before completing design.
    • There are often different ways to strengthen the building. The owner can ask for multiple schemes at the proposal phase and get a contractor to provide cost estimates to find which is cheaper. This could require an additional engineering fee but might save in construction costs.
  • After a conceptual scheme is selected, the structural engineer can develop the final scheme and provide drawings and calculations suitable for a permit.

9.  Submit drawings and calculations to the SFDBI for review for compliance.

  • The owner, structural engineer, or a contractor can submit drawings.
  • The advantage of having the structural engineer submit the drawings and calculations is that they can respond to questions from the plan checker.  But the owner should expect to pay a small fee for the structural engineer performing this task if it is not listed in the structural engineer’s proposal.
  • Often the contractor has not been selected at this point, but they can be selected prior to the plan check if the owner wishes. However, preselecting the contractor could result in the need to re-determine the construction cost if the SFDBI has significant comments that require modifications to the design.

10.  Respond to plan check comments

  • Generally, these will be questions the structural engineer has to answer and may require minor modifications to drawings and/or calculations for re-review. 

11. Identify acceptable contractors and send them drawings to get bids.

  • It is generally better to identify a reasonable number of qualified contractors rather than request bids from every contractor you can find. Qualified contractors may not bid if there is a large number of competitors, especially is some are not qualified and will provide lower costs.
  • Structural engineers can usually provide suggestions for qualified contractors.
  • If you want the job bid in a specific fashion, you need to give the contractors specific instructions. For example, if you want a lump sum bid, but want a unit cost for work associated with pouring additional footing length because you suspect some of the concrete may be weak, you need to ask this so all bids will be easily compared.

12. Hire a qualified contractor

  • If you have difficulty comparing different bids, you can ask the structural engineer for assistance but this may require a small additional fee  if the task is not listed in the structural engineer’s proposal. Sometimes contractors will include exclusions or assumptions that may not be clear to those who do not understand the drawings.
  • When you hire a contractor, you are hiring a general contractor.  Often a general contractor will have subcontractors work for them.  As an example, the general contractor may self-perform all of the wood work but may hire a concrete subcontractor.  

13. Obtain a permit from SFDBI

  • Once SFDBI agrees all of the requirements are met, the contractor, owner, or structural engineer can pick up the permit.  Typically this is done by the contractor. 
  • In order to get a permit, the structural engineer has to fill out a Special Inspection and Structural Observation Form indicating what work requires inspection by a special inspector and observation by the structural engineer.

14.   Hire a special inspector (do not let contractor do this). 

  • The special inspector's job is to perform inspections on specific items during construction (e.g., anchor bolts installed in concrete, welding, etc). He/she is there to ensure quality on the critical items in the project and to be a representative of the City and the structural engineer.
  • The structural engineer can usually provide suggestions and the City has a list of qualified and approved inspectors.
  • The special inspector can provide the owner an estimate for doing the work if they review the drawings. Because they are somewhat dependent on the contractor's schedule, there are sometimes minor adjustments to these fees during the work.
  • Some structural engineer’s offer to be the special inspector and this can be appropriate, depending on the nature of the retrofit.  In such cases, it still may be necessary to hire a Testing Lab to test material strengths. 

15. During construction

  • We recommend a pre-job meeting involving the owner, contractor, structural engineer and special inspector. This could require an additional fee for these parties but is typically worth it to avoid misunderstandings and to open lines of communication.
    • If observation of existing materials were delayed until construction began, this is a good time for openings in walls, etc. to be made.
  • The structural engineer reviews submittals and shop drawings (if required) prepared by the contractor and subcontractors prior to construction. Once they are returned, the contractor can begin fabrication of rebar, etc. Poorly done shop drawings may require resubmittal to the structural engineer for second review, which could result in an additional cost to the owner.
  • The structural engineer will respond to requests for information (RFIs) by the contractor. These RFIs typically involve unexpected conditions or deterioration, or some part of the drawings that the contractor finds difficult to interpret. The structural engineer typically assumes a reasonable number of RFIs in his/her proposal. Additional RFIs could result in additional engineering fees.
    • Some RFIs are suggestions by the contractor to do something in a manner different than the manner specified by the structural engineer.  This may or may not be appropriate.   If the contractor assumed that a cheaper way of doing the work would be acceptable, and it takes the structural engineer some effort to prove it, it may be appropriate for the contractor to pay for this effort unless the contractor can convince the owner it is worth his/her while to do it. 
    • The City inspector will often request to see RFIs when doing inspections, so copies of RFI responses should be kept on the job site for inspections.  It is generally a good idea for the owner to be copies on all RFIs and RFI responses. 
  • The City inspector will visit the site during various stages of the work. Usually the contractor will coordinate this.
  • The special inspector will inspect at appropriate times during the construction as indicated by the structural engineer on drawings and on the form completed by the structural engineer and submitted to SFDBI. The special inspector should be notified by the contractor regarding appropriate times to come to site. Neglecting to do this can be a serious problem and in extreme cases, may require partial demolition of work that was just completed so the work’s quality can be established.
    • In some cases where the special inspector was not called at the appropriate time, the contractor may have to take samples to perform tests on new concrete to verify it is of sufficient quality or pull test anchor bolts installed in existing concrete to verify they are installed properly. These tests are indicated on the drawings.
  • The structural engineer will perform structural observations at appropriate times and should be notified by the contractor when to come to the site. It is possible to save money by limiting the number of observations but this could have negative impact on quality. The structural observations are not inspections or special inspections. The structural engineer is looking for general conformance with the drawings, and would not be doing things like measuring spacing between rebar.  The structural engineer understands the design the best and thus is able to make useful observations about items that the City inspector and special inspector might not detect. 
  • The contractor may also request a site visit by the structural engineer due to questions they have based on a condition they discovered, or a problem they have completing the work shown on the drawings. Usually the structural engineer's contract will allow for a certain number of observation visits and if additional visits are required it will result in an additional fee.
  • The City inspector, special inspector and structural engineer are a team that helps ensure good quality construction.  However, it is still important that the contractor accept responsibility for quality of their own work, and the work of their subcontractors. 

16. Completion of construction

  • At the end of the project the owner and structural engineer should walk the site with the contractor to make sure all structural work appears to be completed and that the finished conditions are acceptable.
  • The structural engineer will provide a letter indicating that work appears to be in compliance with the drawings for submission to SFDBI. This letter is required to complete the work.
  • For an additional fee, the owner can ask for as-built drawings.  The City does not require this.   This will be of more value to the owner if substantial changes were made after the drawings were approved by the City.   At the very least, the owner should archive copies of the permit drawings and RFI responses for possible future use.

For more information about the Soft Story Ordinance, visit the City & County of San Francisco Department of Building Inspection website.

 
 


Contact: 
David McCormick, S.E. | 415.343.3032 | dlmccormick@sgh.com

Kenneth Tam, S.E. | 415.343.3048 | kttam@sgh.com