Unreinforced Masonry Buildings in Los Angeles: What Owners Need to Know

Unreinforced masonry buildings represent one of the most serious seismic hazards in Los Angeles. Constructed with brick, stone, or concrete block walls that lack steel reinforcement, these structures are highly vulnerable to collapse during moderate to strong ground shaking. Los Angeles has thousands of URM buildings, many of them concentrated in older commercial districts, and the city has implemented mandatory retrofit requirements that building owners cannot ignore.

Understanding the risks, the regulatory landscape, and the retrofit process is essential for anyone who owns or is considering purchasing a URM building in Los Angeles.

Why URM Buildings Are Dangerous in Earthquakes

Masonry walls without internal steel reinforcement have very little capacity to resist the lateral forces generated by seismic ground motion. During an earthquake, the mortar joints between bricks or blocks act as planes of weakness. Walls can crack diagonally, bulge outward, or collapse entirely. Parapets — the portions of masonry walls that extend above the roofline — are especially prone to falling because they are unrestrained at the top.

The 1933 Long Beach earthquake caused widespread destruction of URM buildings throughout Southern California and led directly to the passage of the Field Act, which established seismic design requirements for public school buildings. Subsequent earthquakes, including the 1971 San Fernando and 1994 Northridge events, continued to demonstrate the extreme vulnerability of unreinforced masonry construction. Collapsed URM buildings have been responsible for a disproportionate share of earthquake fatalities in California. {/* TODO: internal link to Chimneys, Parapets, and Non-Structural Damage: What Earthquake Insurance Covers */}

Los Angeles Mandatory Retrofit Ordinance

Los Angeles adopted its Division 88 ordinance (later updated and incorporated into Division 91 of the Los Angeles Municipal Code) to require seismic strengthening of URM buildings. The original ordinance, enacted in 1981, established a phased compliance schedule based on building occupancy type, with the highest-risk buildings — those with high occupancy levels such as assembly halls and essential facilities — required to comply first.

Under the ordinance, building owners must either retrofit the structure to meet specified seismic performance standards or demolish it. The retrofit requirements include strengthening or replacing masonry walls, anchoring walls to floor and roof diaphragms, bracing parapets, and in some cases adding new lateral force-resisting elements such as steel frames or reinforced concrete shear walls.

The City of Los Angeles Department of Building and Safety (LADBS) maintains the list of identified URM buildings and tracks compliance status. Buildings that have not complied with the ordinance face enforcement actions, and non-compliance is a matter of public record that affects the property's marketability and insurability.

What a URM Retrofit Involves

The scope of a URM retrofit depends on the building's size, configuration, condition, and intended use. Common retrofit measures include the following.

Wall-to-diaphragm anchoring connects the masonry walls to the wood or concrete floor and roof structures using steel anchors. This prevents the walls from pulling away from the floors during shaking, which is one of the primary collapse mechanisms in URM buildings.

Parapet bracing reduces the height of unbraced parapets or adds steel bracing to prevent them from toppling during an earthquake. Falling parapets are a life-safety hazard to pedestrians and adjacent properties.

Addition of new lateral-force-resisting elements may be required when the existing masonry walls, even after anchoring, do not provide sufficient lateral strength. Steel moment frames or braced frames inserted into the building provide the additional resistance needed.

Diaphragm strengthening addresses weak wood floor and roof systems that cannot adequately transfer lateral forces to the bracing elements. This may involve adding plywood sheathing to existing wood diaphragms or installing new steel drag struts.

A licensed structural engineer must design the retrofit, and the plans require approval from LADBS before construction begins. {/* TODO: internal link to Lateral Load and Seismic Force: How Engineers Evaluate Whether a Building Can Withstand an Earthquake */}

Cost and Financial Considerations

URM retrofits are among the most expensive seismic upgrades a building owner can face. Costs vary widely based on the building's size and the extent of work required, but retrofitting a multi-story commercial URM building can represent a major capital expenditure. Building owners should obtain detailed cost estimates from contractors experienced in seismic retrofit construction and should factor permit fees, engineering design costs, and potential tenant relocation expenses into the total budget.

Some financial assistance may be available. California has at various times offered tax incentives or grant programs for seismic retrofitting, and local jurisdictions occasionally provide financing tools such as Property Assessed Clean Energy (PACE) programs that can be applied to seismic improvements. Building owners should consult with local building officials and financial advisors about currently available options.

Impact on Property Transactions

URM status and retrofit compliance are material facts in any real estate transaction involving these buildings. California law requires sellers to disclose known material defects, and a building's URM classification and compliance status fall squarely within that obligation. Buyers should verify compliance status with LADBS before closing any transaction. Lenders and insurers may also impose conditions related to seismic risk for URM properties. {/* TODO: internal link to How Earthquake Damage Affects Property Values in Los Angeles */}

Key Takeaways

Unreinforced masonry buildings in Los Angeles are subject to mandatory seismic retrofit requirements that carry legal and financial consequences for non-compliance. The risks these buildings pose in earthquakes are well documented and severe. Building owners should confirm their compliance status, engage qualified structural engineers for retrofit design, and address any deficiencies promptly. The cost of retrofitting, while significant, is far less than the potential losses from building damage, liability, and loss of life in a major earthquake.