Seismic Retrofit of Existing Commercial Buildings in Los Angeles: What the Code Requires and What the Process Involves

The Foundation: Why Older Buildings Are Seismically Deficient

The majority of commercial buildings constructed before 1980 in Los Angeles were built under seismic codes that have since been significantly updated in response to earthquake damage data. Three categories of buildings have been specifically identified as having disproportionately high risk of collapse or serious damage in major earthquakes.

Non-ductile concrete (NDC) buildings. Concrete frame buildings constructed before approximately 1976 were typically designed without the reinforcing details that allow concrete to flex and absorb seismic energy without fracturing. These buildings—often called “brittle concrete” structures—were identified after the 1971 Sylmar Earthquake and the 1994 Northridge Earthquake as having serious collapse potential in major seismic events. The City of Los Angeles inventoried approximately 1,500 non-ductile concrete buildings under Ordinance 183893 and has issued mandatory retrofit or demolition orders.

Soft-story wood frame buildings. Wood-frame apartment buildings with open or soft first-floor configurations—typically ground-floor parking or retail with residential above—were the subject of Ordinance 183893 (2015) and its subsequent phases. These buildings can collapse at the first story in a major earthquake because the soft story lacks the lateral stiffness and ductility of the floors above it. While primarily residential, many mixed-use commercial-residential buildings in the Sunset Strip, WeHo, Melrose, and Hollywood districts fall into this category.

Unreinforced masonry (URM) buildings. Brick and unreinforced block masonry buildings are extremely brittle under lateral seismic loading. Los Angeles’s URM retrofit ordinance (Division 88) was enacted in 1981 following the 1971 Sylmar Earthquake and required seismic strengthening of approximately 8,000 URM buildings citywide. Most URM buildings in Los Angeles have now completed mandatory retrofit, but the process continues in buildings that have changed ownership or use classification.

Current LADBS Mandatory Seismic Retrofit Ordinances (2026)

As of 2026, the following mandatory seismic retrofit ordinances are active through the Los Angeles Department of Building and Safety (LADBS):

• Ordinance 183893 / Chapter 4D — Non-Ductile Concrete Buildings: Requires seismic evaluation and retrofit of concrete frame buildings built before 1980 per LADBS-accepted analysis methods. Compliance deadlines vary by building tier
• Ordinance 183893 / Chapter 4E — Soft-Story Wood Frame Buildings: Requires seismic retrofit of wood-frame residential buildings with soft, weak, or open-front first-floor conditions. Implementation is phased based on number of units
• Division 88 (LABC Chapter 88) — Unreinforced Masonry Buildings: The original 1981 ordinance and its subsequent amendments requiring seismic strengthening of URM buildings; enforcement has been ongoing with newer compliance obligations for buildings that change occupancy
• Los Angeles Building Code Section 91.9616 — General Voluntary Seismic Retrofit: Provides an alternative compliance pathway for voluntary seismic improvements that do not trigger full mandatory ordinance compliance

Building owners can check their building’s status under any of these ordinances through the LADBS Mandatory Seismic Retrofit Program portal (ladbsservices2.lacity.org), which maintains a public database of buildings subject to compliance requirements.

When Seismic Retrofit Becomes Required: Change of Use and Substantial Improvement Triggers

Beyond the mandatory ordinances, seismic retrofit can be triggered by two common scenarios that affect any building owner undertaking renovations or a change of occupancy.

Change of occupancy classification. Under the California Building Code (CBC 2022, Section 3408), a change in the use of an existing building to a higher-risk occupancy category can trigger a requirement for the structural system to be evaluated and potentially upgraded to meet current code requirements. The occupancy risk categories run from Category I (low hazard to human life) through Category IV (essential facilities). Converting a Mercantile (M) or Business (B) building to an Assembly (A) occupancy—for example, a church, auditorium, or sports facility—moves the building into a higher occupancy category with more stringent seismic performance expectations. DWD Builders undertook exactly this scope on the change-of-use project at 11675 Glenoaks Blvd in Pacoima, where a grocery market was converted to an A-3 Assembly facility, triggering a structural re-evaluation under CBC Section 3408.

Substantial improvement trigger. The CBC and LADBS define thresholds—typically repairs or alterations valued at 50% or more of the building’s replacement value—beyond which the building must be brought into closer compliance with current seismic code. This “substantial improvement” trigger is why large-scale tenant improvements, additions, or renovations in older commercial buildings frequently include a seismic retrofit component in the construction scope.

How Structural Engineers Evaluate Existing Buildings for Seismic Performance

A seismic evaluation of an existing building begins with the structural engineer obtaining and reviewing the original construction documents, if available, and conducting a field investigation of the as-built conditions. The evaluation methodology is typically governed by ASCE 41-17 (Seismic Evaluation and Retrofit of Existing Buildings), which the CBC and LADBS reference as the standard approach.

The evaluation process includes:

• Tier 1 Screening — a rapid checklists-based review to identify potential deficiencies against benchmark criteria; many non-ductile concrete and URM buildings fail Tier 1 and require deeper analysis
• Tier 2 Deficiency-Based Evaluation — analysis of specific deficiencies identified in Tier 1 using simplified procedures to determine whether they represent actual seismic risk
• Tier 3 Systematic Evaluation — full nonlinear structural analysis modeling the building's expected response under site-specific seismic hazard; required for complex structures or where Tier 2 is inconclusive
• Material testing — concrete core samples tested for compressive strength, rebar assessment through cover scanning, masonry prism testing to establish actual material properties rather than relying on assumed code-era values
• Soil and foundation review — review of existing geotechnical data and assessment of liquefaction risk and foundation adequacy under current seismic demands

Common Seismic Retrofit Strategies for Commercial Buildings

The retrofit strategy selected for a specific building depends on the structural deficiencies identified in the evaluation, the occupancy type, the building’s geometry and materials, and the targeted performance level. ASCE 41-17 establishes performance levels—Immediate Occupancy, Life Safety, Collapse Prevention—and retrofit designs are calibrated to achieve the target level for the building’s occupancy category.

The most common retrofit interventions for commercial buildings in Los Angeles include:

• Shear wall addition — new reinforced concrete or steel-braced shear walls are added to the structural system to increase lateral resistance; typically requires foundation work to transfer the new wall loads
• Column jacketing — concrete columns in non-ductile concrete buildings are wrapped with new reinforced concrete, steel plates, or fiber-reinforced polymer (FRP) composite to add confinement and ductility
• Steel moment frame insertion — new steel moment frames are installed within or around the existing structure to provide ductile lateral resistance
• Base isolation — for high-value or essential facilities, the building structure is isolated from the foundation by seismic isolators (lead-rubber bearings, friction pendulum systems) that absorb seismic energy before it enters the building; very costly but effective for buildings that must remain operational post-earthquake
• Diaphragm strengthening — concrete topping slabs or steel deck systems are added to improve floor and roof diaphragm stiffness and the connection of diaphragms to vertical lateral elements
• Anchor bolt and connection upgrades — in URM and soft-story buildings, adding new anchor bolts between the mudsill and foundation and between roof framing and wall tops is often the primary scope

The LADBS Permitting Process for Seismic Retrofit

Seismic retrofit projects in Los Angeles follow the standard LADBS plan check process but with specific routing through LADBS’s Mandatory Retrofit section when the work is compliance-driven under an active ordinance. The permit pathway includes:

• Preparation of structural retrofit drawings and calculations by a licensed California structural engineer; calculations typically reference ASCE 41-17 analysis methods and CBC 2022 requirements
• Plan check submittal to LADBS — retrofit projects under mandatory ordinances are routed to the Plan Check Engineering section for structural review
• Response to plan check corrections — LADBS may issue correction letters requiring additional analysis, detail clarification, or supplemental material testing data
• Building permit issuance upon plan check approval — contractor may then commence work
• Special Inspections — CBC Chapter 17 requires special inspection of all structural concrete, structural steel, masonry, and high-strength bolt work by a licensed Special Inspector engaged by the building owner
• Final inspection and compliance sign-off — upon completing all required work and inspections, LADBS issues a Certificate of Completion for ordinance compliance; this status is recorded in the city's mandatory retrofit compliance database

What Building Owners Should Understand About Costs and Timelines

Seismic retrofit costs vary enormously depending on building type, deficiency severity, retrofit strategy, and the level of occupant disruption that can be tolerated during construction. The following ranges reflect current Southern California market conditions and LADBS-compliant work scopes, but are not project-specific estimates. Every building requires site-specific evaluation before any cost range can be applied to it.

• Soft-story wood frame (2-4 story, residential above ground-floor commercial): $60,000–$175,000 per building for a standard open-front condition
• URM building (2-3 story brick commercial): $150,000–$500,000+ depending on wall anchoring, parapet bracing, and diaphragm work required
• Non-ductile concrete frame (low-rise commercial, 3-6 stories): $80–$200 per sq ft of building area depending on retrofit intensity and column jacketing vs. shear wall addition
• Plan check and engineering fees: typically 10–20% of construction cost, higher for complex Tier 3 analysis
• LADBS plan check timeline: 3–8 months for a standard retrofit submittal under standard plan check; Priority Plan Check available for fee reduction in timeline

Sources and Further Reading

• ASCE 41-17: Seismic Evaluation and Retrofit of Existing Buildings — American Society of Civil Engineers
• CBC 2022, Chapter 34: Existing Structures — California Building Code
• LADBS Mandatory Seismic Retrofit Program — ladbsservices2.lacity.org
• City of Los Angeles Ordinance 183893 — Non-Ductile Concrete and Soft-Story Wood Frame Retrofit Requirements (2015)
• LADBS Division 88 — Unreinforced Masonry Building Retrofit Program documentation
• FEMA P-58: Seismic Performance Assessment of Buildings — Federal Emergency Management Agency
• Earthquake Engineering Research Institute (EERI): Hall, John F., ed., Northridge Earthquake of January 17, 1994 — Reconnaissance Report
• AISC Design Guide 27: Structural Stainless Steel (for base isolation and damper systems)