What you can build

La Mesa ADU Regulations & Zoning


Size and Separation

Maximum size 1,200 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

How many ADUs can you build in La Mesa?

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).

How many ADUs does La Mesa allow for multifamily properties?

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)

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

What size ADU can you build in La Mesa?

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).

What is the height requirement for an ADU in La Mesa? Can you build a 2-story ADU in La Mesa?

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).

Read more about two story ADUs and height limits.

What are the requirements of the exterior of the ADU?

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.


What is the setback requirement for an ADU in La Mesa?

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

What is the minimum distance the ADU must be from existing structures?

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

Additional Requirements

Does La Mesa require in-person submission of plans for an ADU?

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

Does La Mesa require a soils report for an ADU?

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

Does La Mesa require coastal development permits?

No areas are subject to Coastal requirements.


How many ADUs does La Mesa allow for multifamily properties?

Up to two detached accessory dwelling units shall be permitted on a lot with an existing multifamily dwelling, not to exceed 16′ in height.

Can you stack detached ADUs on top of each other?

This has yet to be tested with the city. However, code notes for lots with multifamily dwelling units, a detached ADU is subject to a maximum of 16 feet in height and one story, so it is unlikely stacked ADUs are permissible.

Can you attach two ADUs to each other in La Mesa?

It is currently undetermined if two detached ADUs can be attached to each other; this will be subject to city interpretation.

Can you convert existing space to an ADU?

Yes, existing non-livable space may be converted to ADUs (e.g. storage areas and garages). The minimum number of ADU conversions allowed is one, up to a maximum equal to 25% of the number of existing multifamily units. This is in addition to the allowed number of detached ADUs..


What is the parking requirement for an ADU in La Mesa?

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.
Where can a parking space be located?

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.