Retrofitting for Peace of Mind: How Apartment Buildings are Upgrading Foundations for Earthquakes

In earthquake-prone regions like California, the safety of residential buildings is a paramount concern. As our understanding of seismic activity and structural engineering advances, many apartment building owners are taking proactive steps to upgrade their properties' foundations and structural integrity. This process, known as seismic retrofitting, is becoming increasingly common and vital, especially for older buildings constructed before modern earthquake safety standards were implemented.

The Importance of Seismic Retrofitting

Earthquakes pose a significant threat to older buildings, particularly those with "soft stories." A soft story is a floor of a building that is significantly less rigid than the floors above it, often due to large openings like garage doors or expansive windows. These structures are particularly vulnerable to collapse during seismic events.

The 1994 Northridge earthquake in Los Angeles served as a wake-up call for many building owners and city officials. This 6.7 magnitude quake caused widespread damage, with soft-story buildings suffering disproportionately. In response, many cities in California have since implemented mandatory retrofitting programs for vulnerable structures.

Understanding Soft-Story Retrofits

Soft-story retrofits are a specific type of seismic upgrade designed to address the inherent weaknesses in these building designs. The primary goal is to strengthen the ground floor to better withstand lateral forces generated by earthquakes. This typically involves adding structural elements like steel frames, shear walls, or moment frames to increase the building's overall rigidity and stability.

Benefits of Seismic Retrofitting

Enhanced Safety: The most obvious and important benefit is increased safety for residents. Retrofitted buildings are much less likely to collapse or suffer severe damage during an earthquake, potentially saving lives.

Property Protection: Retrofitting helps protect the property owner's investment by reducing the risk of structural failure. Severe earthquake damage can render a building uninhabitable and extremely costly to repair.

Insurance Benefits: Many insurance companies offer reduced premiums or better coverage options for buildings that have undergone seismic retrofitting.

Legal Compliance: In areas with mandatory retrofitting laws, completing the upgrades ensures compliance and avoids potential fines or penalties.

Increased Property Value: A retrofitted building can be more attractive to potential buyers or renters, potentially increasing property value and rental income.

Peace of Mind: Both property owners and residents can enjoy greater peace of mind knowing their building is better prepared to withstand seismic activity.

The Retrofitting Process

Seismic retrofitting is a complex process that requires careful planning and execution. Here's an overview of the typical steps involved:

Initial Assessment

A structural specialist conducts a thorough evaluation of the building to identify vulnerabilities and determine the scope of necessary upgrades.

Design Phase

Based on the assessment, a detailed seismic retrofit plan is developed. This includes structural calculations, drawings, and specifications for materials and methods.

Permitting

The retrofit plans must be submitted to local building authorities for review and approval. This ensures the proposed upgrades meet all relevant building codes and safety standards.

Contractor Selection

Once permits are secured, the property owner selects a qualified contractor experienced in soft-story retrofitting. As a note, if you hire a design/build firm (like Alpha Structural), they handle all phases from design, engineering, permitting, and construction. If you don’t have a design/build firm doing your plans, visit our FAQ page for tips on how to choose a qualified contractor.

Construction

• Installing new foundation bolts to better secure the building to its foundation
• Adding plywood or steel shear walls to increase lateral stability
• Installing steel moment frames around large openings like garage doors
• Strengthening connections between floors and walls

Inspection and Approval

Throughout the construction process, inspections are conducted to ensure work is being completed according to approved plans. A final inspection is required to obtain official approval and close out the permits.

Challenges and Considerations

Cost

Retrofitting can be expensive, with costs varying widely depending on the building's size, condition, and the extent of required upgrades. However, many cities offer financing programs to help property owners manage these expenses.

Disruption

The construction process can be disruptive to residents.

Aesthetic Concerns

Some retrofitting methods may alter a building's appearance, which can be a concern for historically significant structures or in areas with strict architectural guidelines.

Engineering Complexities

Each building presents unique challenges, and developing an effective retrofit solution requires considerable expertise.

Case Study: San Francisco's Mandatory Soft-Story Retrofit Program

San Francisco provides an excellent example of how cities are addressing seismic safety concerns. In 2013, the city passed an ordinance requiring the retrofit of all wood-frame soft-story buildings permitted for construction prior to January 1, 1978. This program affects approximately 5,000 buildings in the city.

The ordinance establishes a timeline for compliance based on the building's occupancy and use. Property owners are required to submit screening forms, obtain necessary permits, and complete the retrofit work within specified timeframes.

To assist property owners, San Francisco offers a variety of resources, including:

• A list of pre-qualified contractors and engineers
• Informational workshops and seminars
• Financing options, including Property Assessed Clean Energy (PACE) programs

The city's proactive approach has led to significant progress in improving the seismic safety of its housing stock. As of 2023, over 80% of the affected buildings have either completed retrofits or are in the process of doing so.

Soft-Story Ordinances in LA County

Los Angeles County has implemented various ordinances to address the seismic vulnerability of soft-story buildings. These ordinances require property owners to retrofit their buildings to improve their resistance to earthquakes.

Los Angeles City

The city has a mandatory retrofit program for all wood-frame soft-story buildings constructed before January 1, 1978. The program requires building owners to submit screening forms, obtain permits, and complete the retrofit work within specified timeframes.

West Hollywood

West Hollywood also has a mandatory retrofit program for soft-story buildings. The program requires building owners to complete retrofits within a specified timeframe.

Santa Monica

Santa Monica has a similar mandatory retrofit program for soft-story buildings. The city provides resources and assistance to property owners to help them comply with the ordinance.

Pasadena

Pasadena has implemented a mandatory retrofit program for certain types of soft-story buildings. The program requires building owners to retrofit their structures to meet specific seismic safety standards.

It's important to note that the specific requirements and deadlines for these ordinances may vary. Property owners in these areas should consult with local building officials or experts to determine the exact requirements for their buildings.

Looking to the Future

As our understanding of seismic activity and structural engineering continues to evolve, so too will retrofitting techniques and requirements. Emerging technologies, such as base isolation systems and energy dissipation devices, promise even greater levels of earthquake protection for buildings of all types.

Moreover, the importance of seismic retrofitting is likely to grow as climate change potentially influences seismic activity patterns. Some research suggests that changes in ice coverage and sea levels could affect tectonic stress patterns, potentially altering earthquake risks in some regions.

Conclusion

Seismic retrofitting, particularly soft-story retrofits, represents a crucial investment in the safety and longevity of apartment buildings in earthquake-prone areas. While the process can be complex and costly, the benefits in terms of safety, property protection, and peace of mind are immeasurable.

As more cities implement mandatory retrofitting programs and property owners recognize the value of these upgrades, we can expect to see a significant improvement in the overall seismic resilience of our urban areas. This proactive approach to earthquake safety not only protects lives and property but also contributes to the long-term sustainability and livability of our cities.

For apartment building owners and residents alike, understanding the importance of seismic retrofitting and actively participating in these upgrades is a key step toward creating safer, more resilient communities in the face of seismic threats.