Soft story buildings can be especially vulnerable during earthquakes because the lower level is often more open or less structurally supported than the floors above it. This is common in apartment buildings, mixed-use properties, and structures with tuck-under parking, garage areas, storefronts, or large openings at the ground floor.
The soft story retrofitting process strengthens these vulnerable areas so the building can better withstand lateral movement during seismic activity. Depending on the property, this may involve steel moment frames, shear walls, foundation bolting, grade beams, cantilever columns, or other structural reinforcement methods.
For property owners, the process can feel complicated at first. There may be engineering plans, permit requirements, tenant coordination, construction scheduling, and final inspections to manage. This guide breaks down what to expect from start to finish.
What Is a Soft Story Building?
A soft story building is a multi-story structure with a weaker or more open lower level. These buildings often have parking, garages, commercial spaces, or large window and door openings on the first floor, which can reduce the building’s ability to resist earthquake forces.
During an earthquake, the open lower level may shift more than the upper floors. If the building cannot absorb and distribute that force properly, the lower story may become unstable, increasing the risk of severe damage or collapse.
Common examples of soft story buildings include:
- Apartment buildings with tuck-under parking
- Multi-family buildings built above garages
- Mixed-use buildings with storefronts below residential units
- Older wood-frame buildings with large ground-floor openings
- Buildings with limited lateral support at the first level
Soft story retrofitting helps correct these weaknesses by adding structural support where the building needs it most.
Why Soft Story Retrofitting Matters
Earthquakes place lateral stress on a building, meaning the structure is pushed side to side rather than only downward. A soft story building may not have enough bracing, framing, or foundation connection at the lower level to handle that movement.
A properly designed retrofit can help:
- Reduce the risk of collapse during an earthquake
- Improve the building’s lateral strength
- Protect tenants, occupants, and property
- Help meet local seismic safety requirements
- Preserve the long-term value of the building
- Reduce the likelihood of major earthquake-related repairs
In many California cities, soft story retrofitting may also be required by local ordinance. Requirements vary by jurisdiction, so property owners should confirm whether their building is subject to a local retrofit program.
The Soft Story Retrofitting Process
Every building is different, but most soft story retrofit projects follow a similar sequence. The exact timeline depends on the property’s size, structural condition, local permitting requirements, engineering complexity, and construction scope.
1. Initial Building Assessment
The process usually begins with an on-site evaluation. A contractor or structural engineer reviews the building’s foundation, framing, support columns, parking areas, wall lines, and other vulnerable points.
During this stage, the team looks for conditions such as:
- Weak or open ground-floor walls
- Tuck-under parking areas
- Limited bracing or lateral support
- Aging foundation components
- Large garage, door, or window openings
- Structural elements that may not meet current seismic standards
The goal is to understand how the building is currently supported and where reinforcement may be needed.
2. Engineering Review and Retrofit Design
After the assessment, the engineer develops a retrofit strategy based on the building’s layout, materials, load paths, and seismic vulnerabilities.
The retrofit design may include one or more reinforcement methods, such as:
- Steel moment frames
- Shear walls
- Steel beams or grade beams
- Cantilever column systems
- Foundation bolting
- Supplemental bracing
- Column jacketing
- Fiber reinforced polymer reinforcement
The design should be tailored to the building. A retrofit plan that works for one property may not be appropriate for another, especially if the parking layout, foundation, framing, or architectural constraints are different.
3. Plan Preparation
Once the retrofit strategy is selected, the engineer prepares formal structural plans and calculations. These plans show where reinforcement will be installed, how the load will be transferred, and how the retrofit will bring the building closer to current seismic performance requirements.
This step is important because local building departments typically require detailed documentation before issuing a permit.
4. Permit Submittal and Plan Check
The completed plans are submitted to the local building department for review. The plan check process allows city or county officials to confirm that the proposed retrofit meets applicable codes and ordinance requirements.
In many cases, the first submittal may come back with corrections or requests for clarification. This is normal. The engineer revises the plans, responds to comments, and resubmits the package until the plans are approved.
Permit timelines vary by jurisdiction. Some building departments may offer expedited review, while others may have longer review periods depending on workload and project complexity.
5. Tenant Coordination and Habitability Planning
For occupied multi-family buildings, tenant coordination is often a major part of the process. Some cities require a Tenant Habitability Plan or similar documentation before construction begins. The current Retrofit1 process page references THP guidelines as part of minimizing disruption during construction.
Even when a formal plan is not required, property owners should still prepare for:
- Advance tenant notices
- Parking disruptions
- Temporary access restrictions
- Construction noise
- Safety measures around work areas
- Clear communication about project timing
Good communication helps reduce confusion and keeps the project moving more smoothly.
6. Construction and Structural Reinforcement
Once permits are approved, construction can begin. The contractor installs the approved reinforcement system according to the engineer’s plans.
Depending on the building, this phase may include:
- Excavation for new footings or grade beams
- Installation of steel moment frames
- Foundation bolting
- Placement of shear walls
- Reinforcement of columns or framing
- Concrete work
- Welding, anchoring, and hardware installation
- Repairs to finishes affected by construction
For buildings with tuck-under parking, one of the biggest design goals is often strengthening the structure without unnecessarily reducing parking functionality. The older LA-focused process blog specifically identifies parking loss as a common problem to avoid during retrofit planning.
7. Inspections and Quality Checks
During construction, inspections may be required at different milestones. These can include checks for excavation, reinforcing steel, welding, anchors, framing, concrete, and final installation.
The project team should confirm that the work matches the approved plans before final inspection. Engineers may also perform field observations to verify that key structural elements are installed correctly.
8. Final Approval and Documentation
After construction is complete, the local building department performs a final inspection. Once the work is approved, the property owner receives documentation showing that the retrofit has been completed.
This documentation is important for compliance, future property sales, insurance discussions, and long-term building records.
How Long Does the Soft Story Retrofitting Process Take?
The timeline depends on the size and complexity of the building, the permitting process, the number of plan check corrections, tenant coordination needs, and the scope of construction.
Smaller projects may move more quickly, while larger buildings or properties with complex structural conditions may take several months from initial assessment to final approval.
The main timeline factors include:
- Engineering and plan preparation
- Local plan check review
- Permit approval
- Tenant notices or habitability requirements
- Material lead times
- Construction complexity
- Inspection scheduling
Because permitting timelines vary by city, property owners should start early, especially if they are working under an ordinance deadline.
How Much Does Soft Story Retrofitting Cost?
Soft story retrofit cost varies widely because each building has different structural needs. A small building with a straightforward reinforcement plan will usually cost less than a larger property with complex engineering, limited access, or extensive foundation work.
Major cost factors include:
- Building size and number of units
- Type of structural system required
- Foundation condition
- Parking or access constraints
- Engineering and architectural plans
- Permit and plan check fees
- Tenant coordination requirements
- Construction materials and labor
- Inspection and documentation needs
The older LA-focused process blog noted that plan check fees alone can vary based on building size and complexity, separate from construction plan and build costs. The more useful general takeaway is that owners should budget for both professional design costs and construction costs, not just the visible installation work.
Are Soft Story Retrofits Required?
In some cities, yes. Many California jurisdictions have adopted seismic retrofit ordinances for certain soft story buildings. These programs usually apply to older multi-story buildings with open or weak lower levels, though the exact requirements vary by city.
Some ordinances are mandatory, while others may apply only to specific building types, construction years, or occupancy categories. The newer Retrofit1 process page lists several California cities with soft story ordinance pages, including Berkeley, Beverly Hills, Burbank, Glendale, Hayward, Long Beach, Los Angeles, Oakland, Pasadena, San Francisco, San Jose, Santa Monica, Torrance, and West Hollywood.
Property owners should check their local building department requirements or work with a retrofit contractor familiar with local seismic ordinances.
Common Problems to Avoid During a Soft Story Retrofit
A retrofit can become more expensive or time-consuming when planning issues are missed early. Common problems include:
- Designing a retrofit that unnecessarily removes parking
- Failing to account for doors, windows, or large openings
- Underestimating local permit review timelines
- Starting construction before tenant coordination is complete
- Using a generic retrofit approach instead of a building-specific design
- Not budgeting for plan corrections or inspection requirements
The best way to avoid these issues is to involve an experienced engineer and contractor early in the process.
Questions Property Owners Often Ask
How do I know if my building is a soft story building?
Your building may be considered soft story if it has an open or weak lower level, especially if the upper floors are supported by columns, garages, storefronts, or tuck-under parking areas. A structural assessment can confirm whether the building has seismic vulnerabilities.
Can tenants stay in the building during construction?
In many cases, tenants can remain in the building, but there may be temporary disruptions to parking, access, noise levels, or certain work areas. Requirements vary by city, and some projects may require a formal tenant habitability plan.
Will a retrofit eliminate parking spaces?
Not necessarily. A well-designed retrofit should consider the existing parking layout and aim to preserve functionality where possible. Some reinforcement systems, such as moment frames, are often used because they can add strength while maintaining open space.
Does a soft story retrofit increase property value?
A completed retrofit can make a building more attractive to buyers, tenants, and insurers because it shows that seismic vulnerabilities have been addressed. It may also help protect the property from costly earthquake damage.
What is the first step in the retrofit process?
The first step is a structural assessment. From there, the engineer and contractor can determine what type of reinforcement is needed, what permits apply, and what timeline the owner should expect.
Final Thoughts on the Soft Story Retrofitting Process
Soft story retrofitting is one of the most important steps property owners can take to strengthen vulnerable buildings in earthquake-prone areas. While the process involves engineering, permits, construction, and inspections, it becomes much more manageable when each step is handled in the right order. A properly planned retrofit can improve safety, support compliance, reduce long-term risk, and help preserve the value of the building.