Step-by-Step Overview: Typical Soft Story Seismic Retrofit Ordinance Project

April 15, 2020
Step-by-Step Overview: Typical Soft Story Seismic Retrofit Ordinance Project
Several cities have passed mandatory ordinances requiring owners of certain buildings to undergo a structural screening process to determine if their building contains a potential “soft story” at its lowest level, typically comprised of large open areas compared to the stories above. The process involved in a seismic strengthening program varies from project to project, but generally follows a few key steps.

1. Assumption

You own one or more buildings and have received notice from the local Authority Having Jurisdiction (typically the city), indicating that your building or buildings are in the soft story seismic retrofit ordinance program. The building is not exempted from the program based on its number of units or date of construction.

2. Hire an experienced and qualified Design Professional

A licensed civil or structural engineer can perform the retrofit design. (A civil engineering license is a broader license. Those who go on to get a Structural Engineer license are typically more focused on buildings, and there are some projects such as hospitals and public schools on which only licensed Structural Engineers are permitted to serve as Engineer of Record.) Theoretically, the design professional could also be an experienced architect, but we will assume hiring a structural engineering firm for this example, and will use the term “engineer” to refer to the design professional.

When hiring, look for experience seismically retrofitting existing buildings, specifically soft story buildings. Soft story retrofits have been completed in San Francisco, Berkeley, and Alameda, California, so there are nearby engineers with relevant retrofit experience available. An engineer should also be familiar with the city’s ordinance and associated documents such as technical bulletins. The technical bulletins are updated to reflect input from the Structural Engineers Association of Northern California Existing Building Committee (SEAONC EBC), along with engineers and city officials as work on buildings proceeds.

If you receive proposals from multiple engineers, you should carefully compare what is and isn’t included in the proposed scope of work. Big-picture-wise, you want the proposal to cover all the steps in the table above. However, a simple comparison of fees can be misleading if, for example, one proposal assumes original drawings are available and another doesn’t. Similarly, if one engineer will provide three structural observation visits and another will only perform one, simply comparing total fees is not appropriate.

Things that the engineer will consider when estimating their fee:

  • Size of the building
  • Availability of drawings
  • Irregular building geometry (located on hillside, has lightwells, etc.)
  • Type of foundation (brick foundations are more challenging)
  • Evaluation approach appropriate for use (see step 7 below)

You will need an engineer to perform one or more of the following tasks: completing a screening form, evaluating the building, and designing the retrofit. Some jurisdictions have specific forms, which may require an engineer’s help to fill out. For example, the City of Oakland requires an Evaluation and Schematic Design Report to be completed. The engineer you select to design the retrofit can be the same engineer that performed the screening, or someone else. If the engineer you hired for the retrofit is different, the first question you should ask is if they agree with the conclusions of the screening.

Meet with the engineer and discuss your project before they begin work.

  • Discuss your performance goal. Do you want to just meet minimum ordinance requirements, or do you want more or at least want to consider better performance where it is cost-effective to do so?
  • Share information you have about previous remodels, repairs, or possible deterioration (e.g., roof leaks). A deteriorated or weakened structure will not perform well in a seismic event.
  • Agree on logistics of site access for the engineer to do the evaluation. Generally, the engineer will need to walk through the entire ground floor and portions of the upper floors. The extent the upper floors need to be visited is partly a function of the analysis approach used. Some jurisdictions, such as the City of Oakland, also require evaluating “non-structural” items such as gas lines, chimneys, or masonry partitions to determine if those elements pose a hazard in an earthquake.
  • Decide whether to perform localized destructive exploration to identify conditions (such as presence, size, and spacing of anchor bolts in existing walls) during the evaluation and retrofit phase or make assumptions that are confirmed during construction. This is less likely to be needed if high-quality original construction drawings exist (see step 3 below).
  • Discuss limitations of the retrofit. 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 steel moment frames, which are more expensive than plywood shear walls.
  • Decide if work can be done in one phase. 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. An architect can address waterproofing issues or code compliance to satisfy disability requirements, which are more likely if a building has commercial space below. Mechanical or electrical engineers may be needed to relocate utilities.

3. Obtain existing drawings

If an owner does not have existing drawings, visit the city’s building department to determine they exist in their archives. The engineer can perform this task, but the owner should expect a small fee if it is not included in the engineer’s proposal. An advantage to having the engineer visit the building department is that they can better judge what information will be useful in some cases. There is a fee for reproduction of records, so if the owner self performs this task, he or she needs to make decisions about copying too much or missing valuable information.

If original drawings are not available, the engineer will need a more extensive site visit to develop drawings by taking measurements. This will also require additional fee if not included in the proposal. There are firms that specialize in just producing as-built drawings. This may or may not be more cost-effective than having the engineer you hire do the drawings, because if the specialty firm does the drawings, the engineer will still want to spend time verifying the drawings appear accurate. Note that without original drawings, some portions of the design (such as rebar in concrete footings or depth and extent of foundations) will be unknown.

If original drawings are available, the engineer will need to verify the drawings appear to be accurate through a site visit.

4. Perform a site visit

We recommend that the owner accompany the engineer on at least a portion of the visit so that they can discuss findings and make decisions while at the building.

If there are no structural drawings, the engineer may want to remove some wall finishes. The owner can help decide the most appropriate locations and hire a contractor to open wall finishes (the engineer may be willing to do this if it’s not necessary to close the openings back up) to verify critical information, or the engineer can make assumptions and verify them during construction.

Critical information includes:

  • Presence of brick foundations
  • Wall connections to framing above
  • Wall connections to foundations (anchor bolts, etc.)

The engineer needs to pay attention to things that will affect possible retrofits, including:

  • Do garage door openings have associated garage doors?
  • Do narrow piers between door openings preclude the use of moment frames?
  • Do cantilevered upper floors require strengthening of second-floor diaphragm that could need waterproofing?

5. Evaluate existing material strengths

The engineer can assume default (typically conservative) 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 testing can be done during construction by the special inspector and testing lab. However, if these assumptions are incorrect, the construction project may be delayed if needed changes to the drawings are made.

The owner should understand that using the strength of existing materials such as plaster or gypboard on walls in the analyses (allowed in the ASCE-41 approach discussed in step 7 below) can result in a more cost-effective retrofit. However, this also means that those walls that might typically be viewed as non-structural if they are not bearing walls become part of the seismic load system of the building, and future modifications such as adding doors or windows should not be permitted without engineering input.

6. Potentially conduct a geotechnical review

A geotechnical engineer may be required for the project for sites with apparent poor soils or on a steep hillside. The engineer will inform the owner if a geotechnical engineer is needed. The geotechnical engineer can determine if the soil is indeed poor and provide appropriate recommendations. Typically, the owner hires the geotechnical engineer directly. Engineers can usually suggest geotechnical engineers qualified to do the geotechnical investigation.

Publicly 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). To provide site-specific information, a geotechnical engineer will need to take one or more borings, which could cost $10,000 to $15,000 for a single boring depending on accessibility, unless geotechnical information from a nearby site is available.

In typical soils areas, the engineer can usually use conservative code-allowed soil bearing values in their retrofit design without much effect on the cost of the retrofit. If you hire a geotechnical engineer, they can provide soil capacities for new foundations, which may reduce construction costs. But again, to provide these capacities, they will probably need to take one or more borings.

7. Perform structural evaluation

The engineer performs the evaluation, typically by either hand calculations or a computer analysis. Depending on the jurisdiction, several analysis approaches are available:

  • Chapter A4 of the International Existing Building Code (IEBC), or equivalently Chapter A4 of the California Existing Building Code (CEBC), was written specifically for these soft story buildings. It uses reduced design forces compared to the current building but is very similar to the building code and can be used for all soft story buildings. Only structural materials can be considered as resisting loads, so no credit is assigned to nonstructural finishes such as plaster, gypboard, and stucco. Importantly, only the first floor needs to be evaluated with this approach. Investigation of the construction above the first floor, other than to determine weights, is not required.
  • The Applied Technology Council (ATC) developed a document called P-807 to address concerns of using Chapter A4 that could lead to over-strengthening of the first floor, causing the upper floors to experience more damage. The use of this methodology is permitted in some jurisdictions, such as San Francisco, but is not permitted for use in Oakland.
  • ASCE-41 is a national standard applicable to all existing buildings. It relies on performance-based design rather than prescriptive design. It assigns credit to nonstructural finishes such as plaster, stucco, and gypboard, but requires investigation of construction throughout the upper floors as well as the first floor. This standard is widely used for retrofitting larger buildings.
  • If the subject building is qualified as historic, alternate building regulations in the California Historical Building Code can be used.

If a building is found to meet ordinance requirement as-is, the city may require the engineer to fill out specific forms along with other documentation (e.g., calculations, field investigation report) and submit it to the city. This is unlikely unless the building was previously retrofitted. However, it can happen and generally the engineer will suspect this possibility before they begin the analysis and will provide a proposal with separate phases for evaluation and retrofit design.

8. Develop retrofit schemes

Generally, the owner should ask the engineer to develop the conceptual scheme or schemes 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 most appropriate. This could require an additional engineering fee, but might save in construction costs or avoid building modifications that the owner finds undesirable.

After a conceptual scheme is selected, the engineer can develop the final scheme and provide drawings and calculations suitable for a permit.

9. Submit for review

The next step is to submit drawings and calculations to the city’s building department for compliance review.

The owner, engineer, or a contractor can submit. The advantage of having the 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 engineer performing this task if it is not listed in the 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 (this will provide the owner with a construction fee ahead of time, which is used to determine the permit fee). However, preselecting the contractor could result in the need to re-determine the construction cost if the city has significant plan check comments that require modifications to the design.

10. Respond to plan check comments

Generally, the city will have questions that the engineer has to answer, which may require minor modifications to drawings or calculations for re-review. Unless some extraordinary issues arise that could not be anticipated (typically of a non-structural nature), this service should be included in the engineer’s proposed fee.

11. Identify acceptable contractors and send drawings for bid

It is generally better to identify a reasonable number of qualified contractors, rather than request bids from many. Qualified contractors may not bid if there are many competitors, especially if some are not qualified and will provide lower costs. Engineers can usually provide suggestions for qualified contractors.

If you want the job bid in a specific fashion, you should give contractors detailed instructions. For example, if you want a lump sum bid, but want a unit cost for work associated with pouring additional footing length because the engineer suspects some of the concrete may be weak, you need to ask this so all bids can be easily compared.

12. Hire a qualified contractor

You should hire a contractor who has experience in seismic retrofit work, preferably in more than just smaller projects like houses. There are processes that should be followed on jobs with engineers that smaller contractors may not be familiar with, such as the use of shop drawings to verify that the engineer’s drawings are interpreted properly.

If you have difficulty comparing different bids, you can ask the engineer for assistance, but this may require a small additional fee if the task is not listed in the engineer’s proposal. Sometimes contractors will include exclusions or assumptions that may not be clear to those who do not understand the drawings. Some contractors have been known to bid low and list a lot of exclusions and then increase their fees for change orders for items that were needed but not included in the bid.

When you hire a contractor, you are typically hiring a general contractor. Often a general contractor will have subcontractors work for them. As an example, the general contractor may self-perform all the wood-related work but may hire a concrete subcontractor for the concrete foundation work.

13. Hire a special inspector and testing agency

In the Bay Area, the special inspector and testing agency are usually one company. The engineer can usually provide names of special inspection agencies, and the city has a list of qualified and approved agencies.

Each project has a need for a special inspection and testing agency to perform the work identified on the Special Inspection and Structural Observation Form (see step 13) required by the city.

The special inspector’s job is to perform inspections on specific items during construction (e.g., anchor bolts installed in concrete, welding). They are there to ensure quality on the critical items in the project and to be a representative of the city and the engineer.

The special inspector will write reports to document the results of their inspection. The special inspection reports should be provided to the owner, the contractor, the engineer, and the city as a minimum. The owner should provide the distribution list to the special inspector. If the engineer is not receiving the reports, significant problems can result.

If the special inspector finds a nonconformance, they should immediately contact the contractor. If the nonconformance is corrected, the special inspector can note this in their report. If the nonconformance is not corrected, the inspector should notify all parties on the distribution list.

The testing lab will do things like perform required strength tests for concrete cylinders.

The special inspector and testing agency 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 engineers offer to serve as 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. The special inspector is typically hired by the owner but may be hired by the engineer. They should not be hired by the contractor (this is not permitted by building code), as that creates a conflict of interest.

14. Obtain a permit

Once the Authority Having Jurisdiction agrees that all the requirements are met by the design package, the contractor, owner, or engineer can pick up the permit (typically the contractor). Construction cost is one of the pieces of information required on the permit, which is used to determine the fee. The owner typically pays the permit fee.

To get a permit, the engineer must fill out a Special Inspection and Structural Observation Form indicating what work requires inspection by a special inspector and structural observation by the engineer. The city requires this to try to ensure that the construction quality is as intended. The owner, contractor, and special inspection and testing agency must sign the form.

15. Begin construction

We recommend a pre-job meeting involving the owner, contractor, 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 verification of existing materials (see step 2) were delayed until construction began, this is a good time for openings in walls or other project steps to be made. Required inspections and structural observations should also be discussed.

It is best if the engineer providing construction administration services is the original design engineer, as they are most familiar with the project. On some past projects, contractors have introduced their own engineers to do the construction administration tasks without informing the original engineer. If the engineer is hired by the contractor, they may look after the contractor’s interests, rather than the owner’s. They also may encounter difficulties if unknown conditions are encountered and the design must be changed because they are not the engineer-of-record on the project.

The 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 engineer for second review, which could result in an additional cost to the owner.

The engineer will respond to requests for information (RFIs) by the contractor. This is typically a formal written process that allows questions and answers to be properly documented. This process should probably be more formal than a phone call or an email. RFIs typically involve unexpected conditions or deterioration, or some part of the drawings that the contractor finds difficult to interpret. The engineer typically assumes a reasonable number of RFIs in their proposal. Additional RFIs could result in additional engineering fees.

Some RFIs are suggestions by the contractor to do something in a manner different than what the engineer specified. This may or may not be appropriate. If the contractor assumed that a cheaper way of doing the work than indicated on the drawings would be acceptable, and it takes the engineer some effort to prove it and modify the design, it may be appropriate for the contractor to pay for this effort unless the contractor can convince the owner it is worth their while, and passes on the savings to the owner.

The city inspector will often request to see RFI responses when doing inspections, so copies of RFI responses should be kept on the job site. It is generally a good idea for the owner to be copied on all RFIs and RFI responses.

Despite every effort by the engineer, it is common for unknown conditions to be revealed when finishes are opened or foundations are revealed. This is especially the case when original drawings are unavailable. This can be the result of modifications over the years or poor-quality construction. For example, walls may exist without any type of foundation beneath them and this could not be detected during a walkthrough. In such cases, not only will the project potentially be delayed, but additional engineering fee may be required. Owners should anticipate this possibility.

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 engineer on drawings and on the Special Inspection and Structural Observation Form completed by the engineer and submitted to the city. The special inspector should be notified by the contractor regarding appropriate times to come to site. Neglecting to notify the special inspector to visit 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 or 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.

The engineer will perform structural observations at appropriate times and should be notified by the contractor when to come to the site. As an example, structural observation may be required prior to pouring a concrete foundation because the engineer may want to review the placement of the reinforcing steel.

Required structural observation visits are typically called out on the Special Inspection and Structural Observation Form and the first or second sheet of the structural drawings. It is possible to save money by limiting the number of observations, but this could have a negative impact on quality. The structural observations are not city 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 can make useful observations about items that the city inspector and special inspector might not detect. Detecting problems early can avoid costly delays. Omitting required structural observations can cause major problems at the end of the project (see below).

The contractor may also request a site visit by the 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 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. We recommend a minimum of two structural observations with more visits on larger, more complicated jobs. This is additional to the recommended initial meeting with the owner, the contractor, and the special inspector.

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. This means having a project manager or superintendent visiting the site frequently and being present at key times.

16. Complete construction

At the end of the project, the owner and 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 special inspector is required to provide a letter indicating that all the work they inspected met the requirements of the design. If the contractor did not call them out to inspect portions of the work, this can cause issues that can result in the need for more testing and in extreme cases demolition to verify construction. Therefore, the contractor must be aware of all special inspection requirements.

The engineer is required to provide a letter indicating that work appears to comply with the drawings for submission to the city. To do this, the engineer must receive and review the special inspector’s letter. This letter is required for the city to sign off on the project. If structural observation visits were not completed, this can cause issues that in extreme cases can result in local demolition to verify construction details. Therefore, the contractor must be aware of required structural observations.

For an additional fee, the owner can ask the engineer 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.

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