Soft Story Seismic Retrofits – how much will it cost?
For a typical Los Angeles soft story apartment building requiring 2 moment frames the total cost is likely to be between $50,000 to $65,000 per completed retrofit. A large complex building, requiring 4 or more frames may cost over $100,000.
Costs generally fall into 3 groups:
- Engineering fees
- Construction costs
- Permitting Fees
These generally run from $6,000 to $10,000 per completed and approved set of plans. Usually a senior engineer will be required for 15 to 30 hours and a junior engineer or designer for 40 to 60 hours of work. Senior engineers (a P.E. – Professional Engineer) charge around $150 to $200 per hour and a junior engineer from $90 to $130 per hour. Some engineering companies may offer a single blended rate to cover all engineering (typically $110 or more).
The city of Los Angeles has set out an extensive checklist of documents and calculations including a requirement for certification from a P.E. (Professional Engineer). Any plans submitted not meeting the specifications are returned with corrections (red-lining) for re-submission.
Unless the building owner can provide an “as-built”, building elevations are required and will add about 20 hours of additional site measurement, engineering and drafting. Los Angeles is very unlikely to have copies of the original plans of the soft story buildings given they were constructed prior to 1978.
Some construction companies may offer “Design Build” for a retrofit project and offer low fixed pricing for engineering. The building owner should beware that most companies will aim to recover any discount on the engineering by an additional mark up on the construction, so building owners will end up paying the same when the project is complete.
It is common that some building testing will be required for the engineering. For example, an engineer will need to remove stucco to see the dimensions and quality of pre-existing wood beams and columns, or structural ironwork. This type of testing is termed “destructive” and will eventually need patching. Non-destructive testing with ground penetrating radar (GPR) can also be used and is frequently simpler, quicker and cheaper.
Value Engineering is a key component in finding affordable construction solutions for a property. Value Engineering is the process of evaluating all compliant construction solutions for a structure with the goal of finding the best value option. Often a $15,000 solution can be as compliant as a $50,000 solution depending on the property.
In a few cases a site may have been incorrectly identified as an at-risk soft story building. In these cases the owner needs to submit evidence to the City that the building should be excluded.
It is also expected that a few buildings may have already been retrofitted to a sufficient level – in these cases an engineer is required to submit drawings and calculations and certify that the building is compliant. While the building owner will not have to pay for any more construction, the engineering required is almost the same as if the building had not been already been retrofitted, so the fees could be in the $5,000 to $10,000 range.
In a few cases shear wall strengthening can be accepted by the city of Los Angeles as a potential solution and is cheaper than other construction options such as cantilevered columns or moment frames. However, in most cases, this approach will not provide sufficient strength to meet the requirements – particularly when tuck-in parking and open bays are present. Adding shear wall strength is expected to cost around $5,000 to $10,000 for labor and materials. A good engineer will evaluate whether this lower cost solution will be permitted.
Cantilevered columns are expected to be a popular solution. New concrete footings are laid, often with a grade beam for support. The cantilevered columns are then fastened to existing structural members to transmit the load from the footings to the second floor. A report from Applied Technology Council (ATC) for the San Francisco Soft Story program found cantilevered columns to be an effective solution, but similar in cost and performance to moment frames. One potential advantage is that cantilevered columns may be more space efficient than a moment frame with a beam fixed at the top of the columns. A single bay cantilevered solution is expected to cost around $15,000 to $20,000 fully installed.
Moment frames can be delivered to the jobsite either as 2 columns and a connecting beam, or fully pre-assembled into a single unit. A full frame has 2 columns at the height of the soft story floor (roughly 8’) and the beam the width of the open bay (~8’ to 14’) – although there are many permutations. Moment frames can be bolted or welded in fabrication or at the jobsite. Some units are termed ‘Special’ moment frames – these are distinguished by having a ductile plate or fuse at the connection between the beam and columns. This component is designed to deform under lateral loads from a seismic event and may save the columns and beams from permanent deformation. Costs vary on the exact size and complexity of installation, but roughly $20,000 to $25,000 per installed frame can be expected.
A rough rule is that a moment frame is required for every 2 parking bays. However, this can vary depending on the strength of existing shear walls and pre-existing steel structural supports.
Permit fees are charged directly by the city and range based on a combination of the property specifications and cost of retrofit. Plan Review and Construction permitting fees can be estimated by using the LADBS permit calculator.