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What you can build

La Mesa ADU Regulations & Zoning

KEY RULES AT A GLANCE
Size and Separation

Maximum size 1200 square feet

Side/rear setbacks 4 feet

Two story Yes

Building separation 6 feet

Additional Requirements

Soils Report Yes

Building Verification Survey No

Coastal permit (in some areas) No

Stormwater Mitigation No

Number of ADUs Allowed

  • On La Mesa single-family residential lots, you may build one ADU (either attached or detached) and one Junior ADU (JADUs have an owner occupancy requirement and must be converted from existing space within the primary residence).

  • La Mesa allows up to 2 detached ADUs for multifamily lots with an existing multi-family building. (Meaning: In order to build 2 ADUs, the property must already have at least a duplex on it, not just a single family dwelling). Also note that two separate homes on the same lot are not considered a multifamily dwelling. So you could not build 2 detached ADUs on a property with two existing single family homes on it.

    Effective Jan 2025 (SB1211): Multifamily property owners are permitted to build as many ADUs as there are existing units, with a maximum of eight detached ADUs. This change is due to California state law and will pre-empt existing local laws that are not brought into conformance.

    Non‐livable space within existing multi‐family structures may be converted into an ADU. Examples of areas that can be converted include storage rooms and garage spaces. The maximum number of ADU allowed in a multi‐family structure is equal to 25% of the number of existing multi‐family units in the structure. A minimum of one conversion ADU is allowed.

ADU Size & Building Constraints

  • La Mesa allows for a detached or attached ADU up to 1,200 sqft. ADUs up to 800 square feet are exempt from lot coverage requirements. (Meaning: You can build an ADU of this size even if you’re maxed out on lot coverages).

  • ADUs must comply with the maximum height limitations of the underlying zoning district. So a two story ADU would be possible, even with reduced setbacks of four feet from the rear and side of the property.

    Height limits are either at 20′ or 30′ depending on zone:

    • 20′ Limit: R1E, R1R, R1S, R1, R1A, R2

    • 30′ Limit: R3, RB

    Note that in La Mesa, height of the ADU is measured from the average finished grade to the plate line of the roof (not the peak of the roof).

  • In historic districts, the accessory dwelling unit shall be designed in substantially the same architectural style and finished materials composition as the primary residence or historic structure.

Setbacks

  • ADUs must have 4′ minimum setbacks from rear and side-yard property lines, with front yard setback per zoning standards.

  • The minimum required distance between structures is 6′ from existing structures.

Additional Requirements 

  • No, La Mesa allows digital submission of applications for an ADU.

  • Yes, La Mesa does mandate soils reports for ADUs. They require them at submission of the application.

  • No areas are subject to Coastal requirements.

Parking

  • A parking space is not required for an ADU in any of the following instances:

    • Within a one-half mile walking distance from public transit, which includes bus stops.

    • Within an established historic district.

    • Converted from the existing space of a primary residence or accessory structure, or are attached to an existing or proposed primary residence.

    Effective Jan 2025 (SB1211): When a garage, carport, covered parking structure, or uncovered parking space is demolished or converted for construction of an ADU, replacement parking will not be required.

  • If a parking space is required, it may be located within the setbacks and in an existing driveway as tandem parking. Parking spaces don’t need to be replaced when a garage, carport, or covered parking structure is demolished in conjunction with the construction of an ADU or converted to an ADU.

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