La Mesa Accessory Dwelling Unit Regulations

Introduction to Accessory Dwelling Units

An accessory dwelling unit, commonly called a granny flat or in-law suite must exist on a lot that’s zoned single-family. It has its own entrance, separate from the primary house, as well as a kitchen, bathroom and living space. These units can be rented, year-round, and add a lot of value to a property..

Zoning in La Mesa

ADUs are allowed in lots zoned for single-family or multi-family use. A single-family dwelling must already exist on the property or be built simultaneously with the ADU.

Lot size

There is no minimum or maximum lot size requirement to build an accessory dwelling unit.

Min/Max Building Sizes

Homeowners can build a minimum of 150 sq/ft and a maximum of 1,200 sq/ft for a detached structure.

For an attached ADU the floor area of the ADU should not be more than 50% of the existing residence. For example, if your existing house in 2,500 sq. ft., the attached ADU cannot exceed 1,200 sq. ft. in size.

Height Restrictions

Refer to local building code.

Parking in La Mesa

There are no parking requirements for the City of La Mesa. This is largely because 95% of La Mesa homes are within 1/2 mile of public transit anyway.


A setback is the minimum distance a structure must be away from the street, buildings, or other features.

When an existing garage is converted to an ADU, no additional setbacks are required (given it complies with fire and safety regulations).

For ADU’s constructed above a garage, the setback requirements are five feet from the side and rear lot lines.

Owner Occupancy

ADUs cannot be sold separately from the primary residence. The owner is not required to live in the main residence or the ADU.


There are no restrictions on short-term or long-term rentals.

How to Evaluate ROI

Building an accessory dwelling unit, especially if you intend to keep the property for a few years, represents an enormously beneficial opportunity to maximize your property.

By constructing an accessory dwelling unit you are adding additional square footage to the property. So if you can build a unit for $275 a square foot, but the average value of homes in your neighborhood are worth $400 a square foot you are gaining instant equity through the project. Plus, you also now have the added benefit of a flexible space that can be rented or used for family.

Note: La Mesa passed its own ADU ordinance on March 12, 2019.

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