Duplex vs. ADU in Los Angeles – How Rent Control Rules Differ

In Los Angeles, duplexes and Accessory Dwelling Units (ADUs) can look similar on paper—but rent control treats them very differently. Understanding the rules can help you avoid costly mistakes and make smart investment decisions.

Duplexes – Full RSO Coverage if Pre-1978

A duplex is a property with two separate residential units.

• Pre-1978 Build: If built on or before October 1, 1978, the property is fully covered by the Rent Stabilization Ordinance (RSO). This means:

  • Rent increases are capped (e.g., 3% for July 2025–June 2026, plus 1% if utilities are included).

  • “Just cause” is required for eviction.

  • Units must be registered annually with the Los Angeles Housing Department (LAHD).

• Post-1978 Build: Not covered by RSO rent caps, but still subject to the Just Cause Ordinance (JCO) for eviction protections.

ADUs – The Fine Print Matters

An Accessory Dwelling Unit (ADU) can be a detached unit, an attached addition, or a converted space like a garage.

Here’s how rent control applies:

• Detached ADU (on a pre-1978 lot): The ADU itself is typically exempt from RSO rent caps, but if the main house is rented out and built pre-1978, the main house may now fall under RSO because the property has multiple units.

• Attached ADU (pre-1978 main house): Both the ADU and main house are under RSO for eviction protections. However, due to the Costa-Hawkins Act, the ADU’s rent may be exempt from RSO caps as a “new unit.”

• Converted ADU (garage or interior space in a pre-1978 home): Both units are fully under RSO for rent caps and eviction protections.

Why This Matters for Owners

• Adding an ADU to a pre-1978 property you rent out could trigger RSO coverage for the main house.

• Duplexes have clear-cut rules—ADUs require more careful review because exemptions vary.

• Misclassifying a unit can lead to improper rent increases or unlawful eviction claims.

Thinking about adding an ADU or buying a duplex in Los Angeles? The Borges Real Estate Team can help you understand how rent control will impact your investment. Let’s connect.