Seismic Risk & Retrofit

Los Angeles sits on some of the most studied seismic terrain on earth. The city straddles dozens of active fault systems, and every structure in the region exists within the context of that geological reality. For homeowners, this means that the age of your house, the way it was built, and what you plan to do with it all carry structural implications that most people never think about until something forces the question.

That something is usually one of two events: an earthquake hits and you start wondering whether your house can handle the next one, or you begin planning a renovation and discover that the scope of work triggers mandatory seismic compliance you did not anticipate. Either way, the information below is designed to help you understand where your home fits in the spectrum of seismic risk, what retrofit actually involves, and how to think about the decision clearly.

We manage projects across Pacific Palisades, Bel Air, Malibu, Beverly Hills, Brentwood, and the greater Westside where the housing stock spans every era of LA's building code history. Many of these homes sit on hillsides with complex geological conditions that compound seismic risk. Our work in structural remediation and major renovations regularly involves seismic evaluation, and the questions homeowners ask about retrofit are remarkably consistent regardless of budget or neighborhood.

Last updated: February 2026

1. WHY LA'S BUILDING CODE HISTORY MATTERS TO YOUR HOME

The most important thing to understand about seismic risk in residential construction is that the building code your home was built under determines its baseline structural capacity. Los Angeles has been at the center of American seismic code development since 1933, and each major earthquake has exposed vulnerabilities that the previous code did not address. The result is a housing stock that falls into distinct eras, each with characteristic structural behaviors and known weaknesses.

This is not theoretical. When a structural engineer evaluates an existing home, the permit date is one of the first things they look for, because it tells them which code governed the design and what to expect when they start investigating.

Pre-1933: Before Seismic Code Existed

The 1933 Long Beach earthquake killed 120 people, destroyed or severely damaged more than 120 schools, and exposed the complete absence of seismic design standards in Southern California construction. Before that event, buildings in Los Angeles were designed with no consideration for lateral forces from earthquakes. The devastation prompted the state to pass both the Field Act (governing school construction) and the Riley Act (requiring all California structures to be designed for a minimum lateral force), and Los Angeles adopted its first seismic building code provisions under City Ordinance 72,968 later that year.

Homes built before 1933 in Los Angeles typically feature unreinforced masonry walls, minimal or no connection between the structure and its foundation, no lateral bracing of any kind, and construction techniques that assumed gravity loads were the only design concern. Many of these structures have survived for nearly a century, which can create a false sense of security. They have survived because they have not yet experienced the ground motion they were never designed to resist.

The City of Los Angeles addressed the most dangerous category of these structures through its Division 88 ordinance, formally known as the Earthquake Hazard Reduction Ordinance, which was first enacted in 1981. Division 88 targeted unreinforced masonry bearing wall buildings constructed before October 6, 1933, requiring owners to either retrofit, vacate, or demolish. The program identified approximately 8,000 buildings, and by the mid-1990s, roughly 95% of the remaining stock had been brought into compliance. However, Division 88 focused on commercial and multi-family structures. Single-family homes from this era that were not URM bearing wall construction were not covered, and many remain structurally unimproved.

1933-1971: Basic Provisions, No Ductility

The Riley Act established a statewide minimum lateral force requirement of 0.02g (two percent of the acceleration due to gravity), and Los Angeles went further with its own provisions requiring design for 0.08g for standard buildings. These were meaningful improvements over nothing, but they were based on a rudimentary understanding of how buildings actually behave during earthquakes. The codes of this era treated seismic forces as simple horizontal pushes rather than the complex, cyclic, dynamic loads that earthquakes actually produce.

Homes built between 1933 and 1971 generally have some form of lateral resistance, but it is minimal by modern standards. Foundation connections exist but may be inadequate. Shear walls, if present, are often undersized or improperly detailed. Concrete elements lack the reinforcing steel detailing necessary to prevent brittle failure. The structural systems can resist moderate shaking, but they do not have the ductility - the ability to deform without catastrophic failure - that modern codes require.

The Structural Engineers Association of California published its first comprehensive seismic design recommendations (the "Blue Book") in 1959, and these provisions were adopted into the 1961 Uniform Building Code. This represented a significant advancement in seismic engineering knowledge, but it still predated the understanding of ductile behavior that would come after 1971.

1971-1994: Improved But Pre-Northridge

The 1971 San Fernando earthquake (also called the Sylmar earthquake) was a watershed event for building codes. A magnitude 6.6 event that struck the northern San Fernando Valley, it killed 65 people and caused extensive damage, particularly to reinforced concrete structures, hospitals, and freeway overpasses. The most devastating losses occurred at structures that had not been retrofitted after the 1933 code changes, including buildings on the Veterans Administration Hospital campus.

The post-1971 code revisions were substantial. They introduced significantly higher design forces, new requirements for concrete ductility detailing, stricter provisions for wall anchorage, and tighter drift limits. The 1982 and 1988 editions of the Uniform Building Code continued to refine these requirements. Homes built during this period represent a meaningful improvement in seismic performance. Foundation bolting was becoming standard practice, shear wall requirements were more rigorous, and structural connections were generally better detailed.

However, this era's codes still did not account for vulnerabilities that the 1994 Northridge earthquake would later expose, particularly in steel moment frame connections and in the performance of structures on soft soils. A home built in 1985 is substantially better than one built in 1965, but it was designed under assumptions about ground motion and structural behavior that were later proven incomplete.

Post-1994: Modern Code

The 1994 Northridge earthquake, magnitude 6.7, killed 57 people and caused an estimated $20 billion in damage. Its most significant engineering lesson was the widespread failure of welded beam-to-column connections in steel moment frames, structures that were supposed to be among the most ductile and earthquake-resistant available. The earthquake also confirmed the vulnerability of soft-story wood frame buildings, non-ductile concrete structures, and buildings with poor soil-structure interaction.

The resulting code changes were extensive. The 1997 Uniform Building Code is generally considered the benchmark edition, representing the first comprehensive integration of lessons from both the San Fernando and Northridge earthquakes. Homes built to the 1997 UBC or later editions of what eventually became the California Building Code (through the International Building Code adoption process) represent the current standard of care for seismic design.

If your home was built after 1997, particularly after the 2000s when the California Building Code began adopting the IBC framework, its seismic design is based on the most current understanding of earthquake behavior. That does not mean it is invulnerable, but it means the known failure modes from previous earthquakes have been addressed in its design.

What This Means for Your Home

The practical takeaway from this code history is straightforward. If your home was built before 1978, it was designed under code provisions that are now known to be inadequate in several specific ways. If it was built before 1933, it may have no seismic design at all. The older the home, the wider the gap between its original design capacity and what current codes require.

This does not mean every pre-1978 home is dangerous. Many older homes have performed reasonably well in past earthquakes, particularly well-maintained wood frame structures with good connections and regular geometries. But "reasonably well" in a moderate earthquake is not the same as "safe" in the large event that seismologists expect on Southern California's major fault systems. The question is not whether your house has survived past earthquakes. The question is whether it is prepared for the one that has not happened yet.

2. COMMON RETROFIT TYPES FOR RESIDENTIAL STRUCTURES

Seismic retrofit is not a single procedure. It is a category of structural improvements tailored to the specific vulnerabilities of a given building. The type of retrofit your home needs depends on its construction era, structural system, foundation type, site conditions, and the specific weaknesses a structural engineer identifies during evaluation. Below are the most common retrofit measures for residential structures in Los Angeles.

Foundation Bolting

Foundation bolting addresses one of the most common vulnerabilities in older LA homes: an inadequate connection between the wood-framed structure and the concrete foundation. In many homes built before the 1950s, the wood sill plate (the bottom member of the wall framing that sits on top of the foundation) was simply placed on the concrete with minimal or no mechanical fasteners. During an earthquake, the house can slide off its foundation entirely.

The retrofit involves drilling through the sill plate into the concrete foundation and installing expansion bolts or epoxy-set anchor bolts at regular intervals. Where the existing sill plate is deteriorated, a new pressure-treated sill plate may be sistered alongside or the existing plate replaced. Foundation plates (also called UFP connectors) are an alternative method that can be installed from inside the crawl space without drilling through the sill plate.

For a typical single-family home in the LA market, foundation bolting alone costs between $3,000 and $10,000 depending on the home's perimeter length, crawl space accessibility, foundation condition, and whether the sill plate needs replacement. Homes with limited crawl space access or deteriorated foundations will be at the higher end. This is one of the most cost-effective structural improvements available for older homes, and it is the foundation (literally) of most residential seismic retrofits.

Cripple Wall Bracing

Cripple walls are the short wood-framed walls that sit between the top of the concrete foundation and the underside of the first-floor framing in homes with raised foundations. They create the crawl space. In many older homes, these walls are unbraced or minimally braced, with just the exterior siding providing lateral resistance. During an earthquake, unbraced cripple walls can collapse, dropping the house onto or into its foundation.

The retrofit involves sheathing the cripple walls with structural plywood (typically 15/32-inch structural-grade, APA-rated) nailed to the framing according to engineered nailing schedules. The plywood creates a shear wall that resists lateral movement. Blocking is installed between studs where needed to provide nailing surfaces, and ventilation openings are cut and screened to maintain crawl space airflow.

Combined foundation bolting and cripple wall bracing for a standard single-family home typically runs $5,000 to $15,000. Homes with tall cripple walls, limited access, or structural deterioration will be higher. Hillside homes, where cripple walls can be significantly taller on the downhill side, often require more extensive engineering and construction, pushing costs into the $15,000 to $30,000 range. For homes with complex hillside conditions, the retrofit may need to integrate with broader foundation work.

Soft-Story Retrofit

A soft story is a level of a building that is significantly weaker or more flexible than the stories above it, usually because of large openings (garage doors, tuck-under parking, storefronts) that reduce the amount of wall available to resist lateral forces. During an earthquake, the soft story deforms excessively while the stiffer upper stories remain relatively rigid, often resulting in the upper floors collapsing onto the ground floor.

Soft-story retrofit typically involves installing steel moment frames or plywood shear walls within the open ground floor to provide the lateral strength and stiffness that the original design lacks. Steel moment frames are common in multi-family buildings because they can span garage openings while maintaining vehicle access. For single-family homes with oversized garage openings, the approach may involve a combination of steel frames, reinforced headers, and plywood shear walls on available wall sections.

The cost of soft-story retrofit varies significantly depending on the building size, the number of open wall lines, and whether the work triggers additional upgrades. For a single-family home with a two-car garage soft story, expect $20,000 to $60,000 including engineering. Multi-family buildings covered by the city's mandatory program typically see costs ranging from $60,000 to $200,000 or more depending on unit count and structural complexity. These costs are separate from any interior finish work required after the structural modifications.

Unreinforced Masonry Retrofit

Unreinforced masonry (URM) structures, primarily those built before 1933, are among the most seismically vulnerable building types. The mortar joints between bricks or blocks have limited tensile strength, and without reinforcing steel, the walls can fail catastrophically during moderate to strong shaking. URM retrofit is complex and typically involves some combination of adding reinforcing steel through grouted cores, installing wall anchors connecting masonry walls to floor and roof diaphragms, adding steel frames or concrete shear walls for supplemental lateral resistance, and strengthening parapets and other falling hazard elements.

URM retrofit for residential structures is relatively uncommon in the LA single-family market because most pre-1933 homes are wood frame. Where URM elements exist in residential properties (chimneys, garden walls, retaining walls), the retrofit or replacement of those elements is often part of a broader renovation scope. URM chimneys are particularly common and are a known falling hazard. Many homeowners choose to remove unreinforced masonry chimneys entirely and replace them with lighter materials.

3. LA'S MANDATORY RETROFIT PROGRAMS

The City of Los Angeles has enacted several mandatory retrofit programs targeting the building types most vulnerable to earthquake damage. Understanding these programs matters for homeowners because they define the regulatory landscape around seismic risk, even if your specific property is not directly covered.

The Soft-Story Retrofit Program (Ordinance 183893)

In October 2015, the Los Angeles City Council adopted Ordinance 183893, establishing mandatory seismic retrofit requirements for two categories of buildings: wood-frame soft-story structures and non-ductile concrete buildings. The ordinance was amended by Ordinance 184081 in February 2016 to adjust compliance timelines.

The soft-story provisions apply to buildings that are wood-frame construction with a permit application submitted before January 1, 1978, have a ground floor containing parking or similar open floor space creating a soft, weak, or open-front condition, and contain four or more dwelling units. LADBS identified approximately 13,500 buildings in Los Angeles falling within the scope of this ordinance.

The compliance timeline runs from the date of the Order to Comply: two years to submit a structural analysis or retrofit/demolition plans, three and a half years to obtain a construction permit, and seven years to complete construction.

This is one of the most significant blind spots in LA's seismic safety framework. Thousands of single-family homes across Pacific Palisades, Bel Air, Brentwood, and the broader Westside have ground-floor garages creating a soft-story condition identical to the multi-family buildings the ordinance targets. The structural risk is the same. The difference is purely regulatory. If you own a single-family home with a ground-floor garage and living space above, the city will not require you to retrofit. But the physics of the next earthquake will not make that distinction.

The Non-Ductile Concrete Program

The same ordinance also addresses non-ductile concrete buildings, those constructed with permit applications submitted before January 13, 1977. These structures, built with older concrete construction practices, lack the reinforcing steel detailing that allows modern concrete buildings to flex without breaking during an earthquake. An estimated 1,500 buildings in the city fall within this program's scope, though the ordinance explicitly excludes detached single-family dwellings and duplexes.

The compliance timeline for non-ductile concrete buildings is longer and more phased: three years to submit a preliminary checklist, ten years to submit retrofit plans or proof of prior retrofit, and twenty-five years to complete all construction work. The extended timeline reflects the significantly greater engineering complexity and cost of concrete building retrofits.

In 2025, Los Angeles County also introduced an ordinance mandating seismic retrofit of certain high-rise non-ductile concrete buildings in unincorporated areas, expanding the geographic reach of these requirements beyond the City of Los Angeles proper.

Division 88: The URM Program

Los Angeles was ahead of most cities on unreinforced masonry. The Division 88 ordinance, enacted in 1981, was one of the first mandatory URM retrofit programs in the country. It covered approximately 8,000 buildings constructed before October 6, 1933, with unreinforced masonry bearing walls. The program has been largely successful. By the mid-1990s, the vast majority of covered buildings were in compliance through retrofit, demolition, or change of use. California's statewide URM Law, passed in 1986, subsequently required all jurisdictions in high seismic zones to inventory their URM buildings and establish mitigation programs.

What These Programs Do Not Cover

The common thread across all of LA's mandatory retrofit programs is that they primarily target multi-family and commercial buildings. Single-family homes, the dominant residential building type across the Westside neighborhoods where we work, are largely exempt. This creates a paradox where the building department can tell you exactly which apartment buildings need retrofit but has no program, no inventory, and no requirement addressing the seismic vulnerabilities of the single-family home you live in.

4. VOLUNTARY RETROFIT INCENTIVES

If your home is not covered by a mandatory program, several incentive programs exist to help offset the cost of voluntary seismic retrofit.

Earthquake Brace + Bolt (EBB) Program

The California Residential Mitigation Program (CRMP), a joint powers authority between the California Earthquake Authority and Cal OES, administers the Earthquake Brace + Bolt program. EBB offers grants of up to $3,000 to homeowners who complete a code-compliant seismic retrofit of their home. Income-eligible households (annual household income at or below $89,040 as of 2025) can qualify for supplemental grants of up to $7,000, potentially covering the full cost of a basic brace-and-bolt retrofit.

To qualify, the home must be wood-frame construction built before 1980, have a raised foundation or crawl space, be located in one of the program's eligible ZIP codes (over 1,100 statewide, with extensive Los Angeles County coverage), and be situated on level ground or a slight slope. The program expanded in 2025 to include rental and non-owner-occupied properties for the first time, and more than 32,500 California homeowners have received grant assistance since the program launched in 2013.

The retrofit must be completed by a contractor from the program's trained contractor directory or by the homeowner as an owner-builder, and must comply with CEBC Chapter A3. Registration periods open periodically throughout the year. Current program details are available at EarthquakeBraceBolt.com.

Earthquake Soft-Story (ESS) Grant Program

The ESS program, also administered by CRMP, provides up to $13,000 for qualifying homeowners to retrofit single-family homes with living space over a garage. This targets exactly the soft-story single-family condition that the city's mandatory program does not cover. Eligibility requires owning and occupying a single-family home built before 2000 with habitable space above a garage.

Insurance Premium Reductions

The California Earthquake Authority offers premium discounts on earthquake insurance for homes that have completed qualifying seismic retrofits. The discount varies but can reduce annual premiums by 5% or more, creating a long-term financial return on the retrofit investment. If you carry earthquake insurance (and in Los Angeles, you should seriously consider it), ask your insurer about retrofit-related premium reductions.

A Note on Federal Funding Uncertainty

5. HOW RENOVATION TRIGGERS MANDATORY SEISMIC COMPLIANCE

This is the section that catches most homeowners by surprise. Even if your home is not covered by any mandatory retrofit program, a planned renovation can trigger seismic upgrade requirements that add significant scope and cost to your project.

The California Existing Building Code (CEBC), specifically Sections 317 through 322, establishes the triggers and requirements for seismic evaluation and retrofit of existing buildings undergoing modification. The California Building Code (CBC) also addresses this in its provisions for existing structures. The key concept is that the building code generally "grandfathers" existing structures under the code in effect when they were built, but that grandfather protection erodes as the scope of proposed work increases.

The Primary Triggers

There are five main triggers in CEBC Section 317.3.1 that can require seismic evaluation and potential retrofit when you modify an existing building.

Construction cost relative to replacement cost. When the total construction cost of a renovation (not including furnishings, fixtures, and equipment) exceeds a specified percentage of the building's replacement cost, seismic evaluation and potential retrofit become mandatory. The commonly applied threshold is 25% of replacement cost for initial triggers to engage, with escalating requirements as the percentage increases. When renovation costs exceed 50% of replacement value, the building department can require the existing structure to meet current seismic standards, which effectively means the structure must perform at or near new construction levels. This threshold is a critical planning consideration for any substantial renovation of an older home.

Modification to structural components. If the proposed work increases the seismic forces in any structural component by more than 10% (cumulative since original construction), a seismic evaluation is triggered. This can happen when you add weight to the structure (a heavier roofing material, a second-story addition), when you remove portions of a load-bearing wall, or when you modify the lateral-force-resisting system in ways that redistribute loads.

Structural elements needing repair. If damage (from any cause, not just earthquakes) has reduced the lateral-load-resisting capacity of the structural system by more than 10%, repair triggers seismic evaluation.

Change in risk category. If the modification changes the building's risk category (for example, converting a residential structure to a use with higher occupancy), seismic upgrade may be required.

Changes in design loading. If the proposed work increases story shear demands by more than 10%, the building must be evaluated.

What This Means for Your Renovation

The practical impact of these triggers is significant. If you are planning a major renovation of an older home in Los Angeles, the scope of structural work required may extend well beyond what you see in the architect's design drawings. Opening up a floor plan by removing walls, adding a second story, reconfiguring a garage, or combining rooms can all trigger seismic evaluation, and if the evaluation finds the existing structure does not meet the applicable standard, retrofit becomes part of your project scope.

This is one of the core reasons we emphasize early feasibility assessment on renovation projects. Understanding whether and how seismic triggers apply to your proposed scope is essential to developing a realistic budget and timeline. The worst outcome is discovering a seismic upgrade requirement after design is complete and permits are in review, when it is too late to adjust the scope without significant redesign.

The interaction between renovation scope and seismic triggers is also central to the tear down versus renovate decision. In some cases, the seismic upgrade cost triggered by a major renovation is significant enough that demolition and new construction becomes the more rational path, particularly when the existing structure is pre-1971 and far below current code standards. This calculation is project-specific and depends on the existing structure, the proposed scope, site conditions, and the owner's goals.

Strategic Considerations

Homeowners and their architects sometimes try to structure renovation projects to stay below seismic trigger thresholds. This can be a legitimate strategy when the proposed work genuinely fits within those limits, but it requires careful analysis by a structural engineer who understands both the existing building and the proposed modifications. Artificially constraining a renovation to avoid seismic compliance can result in a project that does not achieve the owner's goals, or worse, a project that technically avoids the trigger but leaves the building with known structural deficiencies.

6. WHAT RETROFIT COSTS AT DIFFERENT SCOPE LEVELS

Retrofit cost varies enormously depending on the scope of work, the size and complexity of the structure, site conditions, and the specific vulnerabilities being addressed. The ranges below reflect current conditions in the Los Angeles residential market and are intended as planning-level guidance, not estimates for any specific project.

For a detailed breakdown of how these costs fit into broader project budgets, see our construction cost guide.

7. AFTER THE NEXT EARTHQUAKE: WHAT YOU NEED TO KNOW

Every time a moderate earthquake hits Southern California, the same pattern repeats. Search interest in seismic retrofit spikes dramatically. Homeowners who felt their house move in ways they did not expect start asking questions they should have asked years earlier. Structural engineers and retrofit contractors see a surge in demand that fades within weeks as the urgency dissipates.

The reality is that seismic retrofit is most valuable when it is done before the earthquake, not after. The cost of a basic foundation bolting and cripple wall bracing project is a small fraction of the cost of repairing a home that has slid off its foundation. A $10,000 retrofit can prevent $200,000 or more in damage, and more importantly, it can prevent injury or worse.

If you are reading this page because a recent earthquake prompted you to think about your home's structural integrity, that instinct is correct. Use it. Get a structural evaluation from a licensed engineer. Understand what your home needs. Make an informed decision about how and when to address it. Do not wait for the urgency to fade.

If you are reading this because you are evaluating a home to purchase, particularly an older home in the hillside communities of Pacific Palisades, Bel Air, or Malibu, a seismic evaluation should be part of your due diligence. Understanding the seismic condition of the structure before you close gives you the information needed to negotiate appropriately and budget realistically for any improvements you plan.

And if you are planning a renovation of an existing home, understand that seismic evaluation is not optional in the way that choosing countertop materials is optional. It is a structural and regulatory reality that will shape your project scope, budget, and timeline whether you plan for it or not. Planning for it early is always better.

The information on this page is provided for educational purposes and reflects the professional experience and perspective of Benson Construction Group. Cost ranges, timelines, and regulatory references reflect current conditions for the greater Los Angeles area and may vary based on project-specific conditions, site complexity, regulatory requirements, and market fluctuations. Building codes and incentive programs are subject to change. Verify current requirements with LADBS and program administrators before making project decisions. This content does not constitute professional advice for any specific project. Consult qualified professionals, including a licensed structural engineer, for project-specific guidance.