The Structural Engineers Association of Northern California (SEAONC) has provided the following frequently asked questions (FAQ) to provide building owners who may have questions related to the City of San Francisco's mandatory Soft Story Retrofit Ordinance. These questions and answers are related to those items frequently encountered in the practice of structural engineering. If you have a particular question, feel free to email the SEAONC office and we will do our best to answer it.
What is San Francisco's Soft Story Ordinance?
The United States Geological Survey (USGS) predicts a 63% chance another large earthquake will strike San Francisco in the next 30 years.1 The intensity of that event is expected to rival, if not exceed, those of the 1989 Loma Prieta Earthquake and the 1994 Northridge Earthquake. San Francisco enacted the Soft Story Ordinance in 2013 because of its exposure to this earthquake hazard. The ordinance's purpose is to mitigate soft story buildings' risk to damage and collapse due to strong earthquake ground shaking, and to thereby diminish the amount of uninhabitable housing following an earthquake disaster.
What is a "soft story building"?
For the purposes of the Soft Story Ordinance, a "soft story building" is defined as a wood-framed building, constructed prior to 1978, standing three or more stories, containing five or more residential units, and featuring large windows or garage doors at the ground level story as illustrated in Figure 1.2
Why are "soft story buildings" considered dangerous?
Past earthquakes have demonstrated that soft story buildings are particularly vulnerable to severe damage or collapse in a major earthquake relative to other building types. Collapse itself poses a safety to risk to occupants. Additionally, collapse could ignite fires that threaten the safety of occupants and neighboring buildings. The City estimates 43% to 85% of soft story buildings will be uninhabitable following a major earthquake. Such widespread damage could displace 58,000 residents, 2,000 businesses, and the 7,000 employees associated with those businesses.3 Devastation of this magnitude could impede the City's disaster recovery and future economic welfare.
Figures 2 and 3 illustrate the characteristically dangerous behavior which soft story buildings can exhibit in a strong earthquake. These buildings were located in San Francisco, and they are shown in their post 1989 Loma Prieta Earthquake state. In Figure 2, note the second, third, and fourth floor stories are apparently unaffected by the earthquake, but the ground level story is laterally distorted, thereby exhibiting characteristic "soft story" behavior. The ground story distortion renders the building vulnerable to imminent collapse.
Figure 3 illustrates a building that has collapsed. The second and third stories are visible, but the ground level story is not. The second and third stories have collapsed onto the ground story.
I received a notice from the City stating my building is a "soft story building" and I am required to complete a "Screening Form." What steps must I take to comply with the soft story ordinance?
The notice indicates that the City believes your building is subject to the Soft Story Ordinance. In general, most owners will have to take the following actions:
- File Screening Form: Retain a structural engineer to assist with preparing the Screening Form. Screening Forms must be filed with the City's Department of Building Inspection (DBI) on or before September 15, 2014. In some cases, an engineer may be able to justify that a building the City believes is a soft story building is not actually a soft story building, and therefore not subject to the Soft Story Ordinance. In this case you would file, with the assistance of your engineer, the "Optional Evaluation Form."
- Develop retrofit design: Retain a structural engineer to develop a seismic retrofit design for your building. In general, a seismic retrofit will often entail installation of structural steel framing in strategic locations at the ground level or the installation of properly fastened plywood to the wall studs at strategic locations on the ground level. In some cases, this work may also require the removal and re-installation of interior wall finish at strategic locations if present. Some foundation work may also be required. The retrofit is intended to diminish the degree of damage your building will suffer following a major earthquake, and to mitigate the risk that the building will become uninhabitable. It is important to recognize that the amount of seismic strengthening required by the ordinance specified is calibrated ton a level to simply reduce the risk of damage during a large seismic event. It does not a guarantee your building will survive earthquake damage free, nor is it a guarantee your building will not collapse. The engineer's retrofit design is documented on drawings and in calculations the engineer prepares. As an owner, you can always ask your engineering to explore strengthening options which will provide an increased level of protection for your building.
- Obtain original drawings and perform investigation: In consultation with your engineer, inquire at the City’s DBI whether drawings or other documentation about your building are on file at the DBI. Depending on the availability of such documents, you may have to conduct a building investigation, in consultation with your engineer, to assess existing conditions. Investigations usually entail removal of small areas of wall or ceiling finishes in strategic locations to reveal concealed structural conditions. The investigation phase may be the appropriate time to ascertain whether hazardous materials are present in areas where seismic retrofit work will occur. Hazardous materials in older vintage buildings often include lead based paint and asbestos laden insulation around pipes. An industrial hygienist may need to be retained to obtain specimen samples and to analyze the specimens for the presence of hazardous materials.
- Retain Special Inspection firm: In consultation with your engineer, retain a firm that provides Special Inspection services. Special Inspection is a quality assurance process the building code mandates for certain types of structural work.
- File building permit application: File the drawings and calculations with the DBI along with a building permit application. The ordinance requires owners to file building permit applications on or before one of the four following dates: September 15, 2015; September 15, 2016; September 15, 2017; or September 15, 2018. The deadline date that applies to a particular building depends on the building's "compliance tier," which the ordinance defines. A building's compliance tier depends on its occupancy type, occupant quantity, and soil conditions.
- Address plan review comments: Retain the structural engineer that prepared the drawings and calculations to review comments—referred to as “plan review comments--to the drawings and calculations that the DBI staff prepares during their review. DBI staff is charged with enforcing the requirements of the Soft Story Ordinance. Plan review comments list areas of the drawings and calculations that the DBI believes do not conform to the ordinance's requirements. Resolution of the plan review comments with the DBI will be necessary before the DBI will grant a building permit. The construction phase cannot lawfully commence without a building permit.
- Solicit bids from general contractors: Consider retaining the structural engineer that prepared the drawings and calculations to assist with soliciting bids from general contractors to construct the retrofit and to advise you on this process. This could help ensure the most qualified contractors are chosen and that their bid proposal reflects the design requirements. This should also facilitate communication between the potential bidders and the design engineer.
- Retain a general contractor: From among the contractor bidding pool, select the contractor that best meets your qualification criteria. Consider retaining your structural engineer to advise you on this process.
The File Screening Form states my building may not be subject to the soft story ordinance, in which case I can file an "Optional Evaluation Form." What is this process?
Some buildings may not be subject to the Soft Story Ordinance even though the City sent a notice. In some cases, the building may have been voluntarily seismically retrofitted before the ordinance was enacted in 2013. In other cases the building's structural design may be of a type that meets the ordinance's requirements. It is also possible the building is exempt from the ordinance per se because it is not a soft story building as defined in the ordinance. In recognition of these possibilities, the DBI has established a process by which an owner can demonstrate his/her building is exempt from the ordinance. The owner's structural engineer completes the Optional Evaluation Form along with supporting technical documents, and files the form with the DBI. The DBI will review the documents to determine whether they demonstrate that the building complies with the ordinance. There is a reasonable chance the owner will have to retain her/his engineer to respond to plan review comments the DBI issues before the DBI renders its final decision on whether the building is not subject to the ordinance.
What does a structural engineer do? How do I select a structural engineer?
According to Section 6701 of the State of California Business and Professions Code, a structural engineer renders services for the design of structures and buildings that require education, training and experience in engineering sciences and that require application of special knowledge of mathematics, physics and engineering sciences. California law restricts the individuals entitled to practice engineering to those who are licensed by the State.
Structural engineers are licensed professionals. The process of retaining a structural engineer is the same as that employed when hiring an accountant, attorney, doctor or other similar such professional. Evaluation of credentials and qualifications is a key consideration. Selection of a professional solely on the basis of the lowest fee can heighten the risk of an unfavorable project outcome. Fee based selection is appropriate when buying a commodity, but not when procuring professional services. In soft story retrofit projects, engineering fees could amount to approximately 20% of a project's total cost for design and construction, yet the engineering services are critical to determining the other 80% of the project's cost. Projects on which the engineer is retained on a low-bid basis tend to save owners a small amount on up-front design costs, but can result in significantly higher construction costs.
Consider consulting this publication that the California Board of Professional Engineers and Land Surveyors published for insights on retaining engineers.
Sources for identifying licensed engineers include the referral list that the Structural Engineers Association of Northern California (SEAONC) maintains, the telephone Yellow Pages, and the internet.
Consider identifying three or more candidates, request a written services proposal, and interview the candidates after the proposals have been reviewed. Inquire about past experience with projects similar to your own, and request references from the candidates of past clients whom you can contact. Ensure the candidates are California licensed engineers in good standing here.
Pursuant to State law, engineers are required under most circumstances to furnish written agreements to clients before providing engineering services. The agreement should as a minimum describe the proposed services, the compensation basis, the engineer's address and license number, the terms and conditions concerning additional services, and the procedure by which either party can terminate the agreement.
Consider conversing with candidate engineers about project circumstances that are beyond the engineer's control, how such circumstances will be addressed, and the compensation basis for addressing them. Common circumstances engineers are requested to address but cannot anticipate at the time they formulate their scope of services include the extent of plan review comments that the DBI issues during the building permit application process; and construction phase situations such as contractor substitution requests, encountering unforeseen conditions that conflict with the proposed work, queries from City inspectors, and queries from the owner's Special Inspectors.
I have received proposals from multiple engineers. Why do the services scopes and fees vary?
In preparing fee proposals, engineers formulate the scope of services they anticipate will be required to complete a project. Sources for disparity in scopes or fees could include differing understandings of the project's objectives, differing opinions on the means by which project objectives can be attained, or differing understandings in responsibilities assigned. For example, one candidate may include in her/his scope of services response to plan review comments from the DBI, while another candidate may exclude such from his/her basic services but intends to provide such as an additional service on an as-needed basis. During the selection process, inquiring about these disparities while interviewing candidate engineers can be an effective means of ascertaining the basis for scope of services or fee variations among candidates.
My Engineer states there are three engineering methodologies (IEBC4 Appendix A4, FEMA P-8075, and ASCE 416) that can be applied demonstrate conformance to the Soft Story Ordinance. Why are there multiple approaches?
The Soft Story Ordinance permits the engineer to choose from among three different engineering approaches to demonstrate compliance with the ordinance. The intent of all three procedures is to provide a soft story retrofit design that mitigates the building's risk to damage and collapse in a strong earthquake, and to thereby diminish the amount of uninhabitable housing following an earthquake disaster. Evaluating the unique circumstances associated with each project will be informative in determining which procedure to apply. Consider authorizing the engineer at the outset of the design phase to study how the three procedures apply to the project and to determine which procedure best suits the project's objectives. If this option is desired, this is likely to entail a greater proposal fee from the engineer but there is also a good potential for decreased construction costs due to the need for decreased structural elements or those which are better suited to strengthen your building.
The engineer's proposal includes design phase visits to the building to review its condition. Is this necessary?
The process of designing a soft story retrofit begins with defining the existing structural system so that an accurate assessment of its anticipated seismic performance can be made. Where strengthening is required, it is important for the engineer to understand, to the best of their ability based upon the site visit(s), visible project constraints and other existing conditions that may influence the selection, proportion, or placement of the required supplemental structural elements.
After the engineer establishes the structural solution, s/he assesses how the proposed structural components will integrate into the building. In the absence of reliable drawings that depict the locations of a building's existing features, the engineer must visit the site to review such features. The presence of garage door openings, air ducts, electrical conduit, water pipes, sewage pipes, fire sprinklers, etc. can impact where structural components can be placed. In instances where an existing feature obstructs where a new structural component can be located, the engineer and the owner must evaluate the costs and benefits of redesigning the structural solution or relocating the existing feature. It is considered good practice, to the extent practicable, to identify these conflicts during the design phase rather than during the construction phase. Relying on the contractor to resolve such conflicts during the construction phase tends to precipitate schedule delays and cost overruns.
Building features that can obstruct placement of new structural components are often concealed behind wall finishes, ceiling finishes, or are buried underground. It is good practice to undertake an exploratory demolition exercise during the design phase to reveal the locations of potentially obstructive features. Exploratory demolition entails removal of portions of the existing finishes such as wall or ceiling finishes or potentially excavating the earth in some strategic locations to determine the depth of foundation systems or location of site utilities. While exploratory demolition may pose an inconvenience and a small initial expense, it is an effective means to hedge against encountering unforeseen conditions during the construction phase. Encountering unforeseen conditions during the construction phase are common sources of schedule delays and cost overruns.
A candidate engineer discussed the idea of designing a retrofit that provides an enhanced level of performance beyond the Soft Story Ordinance. What does that mean?
The intent of the Soft Story Ordinance is to create a retrofit that mitigates a soft story buildings' risk to damage and collapse due to strong earthquake ground shaking. Compliance to the ordinance's minimum requirements is not a guarantee that a building will not suffer significant damage following an earthquake. A soft story building that suffers damage to the degree it is barely habitable during disaster recovery and does not collapse, but must be demolished following disaster recovery is considered to have performed consistently with the intent of the ordinance. The ordinance contemplates attaining a threshold level of seismic safety that seeks to balance risk mitigation improvement and cost.
Some owners' risk tolerance may lead them to seek a retrofit design that yields a greater margin of safety against damage or collapse risk. Asset value protection such that the building can be indefinitely habitable may be their seismic performance goal. In some projects the incremental design fee cost and construction cost could be offset by the incremental value the owner realizes in the form of enhanced safety and diminished damage potential.
Will I need to hire design professionals other than an engineer?
If the seismic retrofit work scope alters the building's exterior appearance, fire safety rating, parking capacity, disabled persons' access, or historic fabric in cased where the building is listed on a recognized register of historic places, the involvement of a licensed architect may be necessary to consult on these matters. The planning code and the building code regulate these facets of a building.
If the seismic retrofit work scope alters the building's mechanical, electrical or plumbing systems, the involvement of engineers versed in these systems may be necessary.
Older vintage buildings commonly contain hazardous materials, such as asbestos pipe insulation; lead based paint or certain ceiling finish treatments containing asbestos ingredients. If the retrofit work scope disturbs materials containing hazardous materials, a professional versed in hazardous materials identification may have to be consulted. Laws at various governmental levels regulate the handling and disposal of hazardous materials.
What does a contractor do? How do I select a contractor?
A contractor is a licensed firm or individual responsible for constructing the work scope defined on the drawings the engineer prepares. The contractor's responsibilities ordinarily include barricading the site to protect occupants and passersby, hiring specialty subcontractors, such as concrete contractors, steel fabricators, steel erectors, carpenters, etc., coordinating the activities of the subcontractors, and conversing with DBI inspectors and the owner's Special Inspectors to ensure work is progressing in compliance with approved drawings. In short, the contractor is usually the party in control of and responsible for conditions at the construction site during the construction phase.
The telephone Yellow Pages, the internet, and "word of mouth" are sources for identifying contractor candidates. It is good practice to solicit written bids from three or more contractors. California law requires contractors to be licensed, bonded, and insured with workers' compensation and general commercial general liability coverage. Familiarity with mechanics lien law is a worthwhile undertaking to understand liability exposure owners face in construction projects. Consult the California Contractors State License Board for information here.
During the contractor selection process, an important topic for discussion with candidate contractors will be the means and methods each contractor intends to employ to accomplish the work. Worthy questions to pose include: What are the work hours? Will noisy equipment be employed and at what times of the day? Where will workers park? Will the contractor arrange for parking permits for the workers? What is the staging area for the work and where will safety barricades be located? From where will the contractor draw power and water and are costs for those utilities included in the bid? Where will materials be stockpiled? Will the work impact my tenants' ability to park? Will my tenants have to vacate their units? Will the work be undertaken in one phase, or will the work be performed in multiple phases?
San Francisco building stock includes many older vintage buildings that contain hazardous materials, such as asbestos insulation around pipes or lead based paint on walls and ceilings. Determining the presence of hazardous materials in the area of work is an important consideration in defining the project's overall work scope. Ideally the presence of hazardous materials can be determined before the contractor solicitation process occurs. Laws at various governmental levels regulate the handling and disposal of hazardous materials. Contractors ought to know whether they will be responsible for hazardous materials work when preparing their bids. Many contractors that are licensed and experienced with soft story retrofit type work will not undertake hazardous materials abatement work as they lack the necessary licenses or their insurance policies will not cover such work. Owners may have to retain a separate contractor specializing in hazardous materials abatement to remove the hazardous materials before the soft story retrofit contractor can begin work.
What is a Special Inspector?
The building code requires certain types of work to be inspected by a Special Inspector as a quality assurance measure. The Special Inspector must be retained by the owner. Special Inspection Items should be listed on the building plans as well as the ‘statement of special inspection’. The building code prohibits the contractor from hiring Special Inspectors. The DBI maintains a list of firms prequalified to provide Special Inspection services here.
How much time should I expect the retrofit to take?
Construction duration varies depending on many factors, including building size, retrofit work scope, workers' accessibility to the work areas, project phasing constraints (e.g. can the contractor complete the work in one phase, or does s/he complete one portion of the work, demobilize, remobilize and complete the balance of the work to accommodate tenants' relocation), and inclement weather. Soft story retrofit project durations can generally be expected to last from several weeks to several months. Encountering unforeseen conditions during the construction phase, such as buried utilities obstructing new foundation, or pipes or electrical conduit concealed behind wall or ceiling finishes obstructing installation of new structural components can be aggravating circumstances which pose schedule delays.
What will happen to a retrofitted building after a major San Francisco earthquake?
The intent of the Soft Story Ordinance is to mitigate soft story buildings' risk to damage and collapse due to strong earthquake ground shaking, and to thereby diminish the amount of uninhabitable housing following an earthquake disaster. There is no guarantee a building retrofitted to comply with the ordinance's minimum requirements will not suffer damage or collapse following an earthquake.
1 2007 Working Group on California Earthquake Probabilities, 2008, The Uniform California Earthquake Rupture Forecast, Version 2 (UCERF 2): U.S. Geological Survey Open-File Report 2007-1437 and California Geological Survey Special Report 203.
2 Mandatory Seismic Retrofit Program - Wood-Frame Buildings, City and County of San Francisco Ordinance No. 66-13, March 25, 2013.
3 Here Today - Here Tomorrow: The Road to Earthquake Resilience in San Francisco, A Community Action Plan for Seismic Safety, 2010 by the Applied Technology Council.
4 International Existing Building Code (IEBC), International Code Council, 2012.
5 Seismic Evaluation and Retrofit of Multi-Unit Wood-Frame Buildings With Weak First Stories, Federal Emergency Management Agency (FEMA) Publication P-807, May 2012.
6 Seismic Evaluation and Retrofit of Existing Buildings, American Society of Civil Engineers (ASCE) Publication 41, 2006 & 2013.