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LotlineADU permit guides

City notesSan Diego County, California

ADU permits in the City of San Diego

San Diego goes further than state law in several places, most visibly on setbacks. It also has more conditions attached than its reputation suggests, and a different rulebook near the coast.

At a glance

1,200 sq ft
maximum for an attached or detached ADU1
31 days
minimum lease term for an ADU1
30 days
review time with a preapproved plan1

Key points

  • A new ADU can be built up to the side and rear property line, unless the building code requires separation.1
  • Over 16 feet tall next to residential property, a 4-foot setback returns.1
  • In a Very High Fire Hazard Severity Zone, 4 feet applies at any height.1
  • Parts of the bulletin don't yet apply in the Coastal Overlay Zone.1

State rule and San Diego practice, side by side

Where the two say the same thing, and where they differ.

Side and rear setback

California statute

For a new ADU that is not a conversion, the side and rear setback a city requires can be no more than four feet.2

San Diego

A new detached ADU may encroach into the zone's side and rear setbacks, up to the property line, unless the California Building Standards Code requires otherwise.1

The city allows less than the four feet state law permits a city to require. Fire separation rules in the building code still decide how close a wall with windows can sit.

Fire sprinklers

California statute

An ADU does not need fire sprinklers if they are not required for the primary residence.2

San Diego

An ADU must have automatic fire sprinklers if the primary dwelling on the premises is protected by a sprinkler system.1

Replacement parking

California statute

When a garage, carport or parking space is demolished for or converted to an ADU, the local agency cannot require replacement off-street parking.2

San Diego

No parking spaces are required for ADUs outside the Coastal Overlay Zone.1

The document to read

San Diego publishes its ADU building permit guidance as Information Bulletin 400, and the version in force when we read it is dated January 2026.1 A building permit is required for every ADU and JADU, with no exemptions.1

How many, and how big

On a lot in a single dwelling unit zone, the city allows one attached or detached ADU, one more converted from existing space, and one JADU.1

An attached or detached ADU can be up to 1,200 square feet of gross floor area.1 Conversions of an existing accessory structure or part of the house aren't held to that cap.1 And where the existing house has already used up the zone's floor area ratio, one ADU of up to 800 square feet can still be built.1

Setbacks, with the conditions that matter

The headline is that a new ADU may encroach into the side and rear setbacks all the way to the property line.1 Three conditions narrow it:

  1. Height. Beside a residential neighbor, a structure over 16 feet has to keep a minimum of 4 feet at the interior side and rear, or the zone's own setback if smaller.1
  2. Fire hazard zone. In a Very High Fire Hazard Severity Zone, the 4 feet applies whatever the height.1
  3. Fire official. The Fire Code Official can require more, and so can a Brush Management Zone.1

At the front, the ADU observes the zone's setback, though one ADU of 800 square feet or less may encroach into it.1

Near the coast

The bulletin opens with a warning that some of its rules aren't effective in the Coastal Overlay Zone, because later ordinances are still awaiting Coastal Commission certification.1 A Coastal Development Permit is required there for ADUs and JADUs that aren't wholly inside the existing primary structure, that add habitable area, or that convert non-habitable space.1

Living in it, renting it, selling it

  • The owner doesn't have to live on site.1
  • An ADU can't be leased for less than 31 consecutive days.1
  • ADUs may be subdivided into condominiums and sold separately, under conditions set out in the Municipal Code.1
  • A JADU needs a recorded Junior Unit Agreement before its permit is issued.1

What to submit

Applications are made digitally through an Online Permitting Account.1 Besides the plans and calculations, three forms are listed: the General Application (DS-3032), the Water Meter Data Card (DS-16) and the Storm Water Applicability Checklist (DS-560).1

A newly built detached ADU that isn't a manufactured unit falls under the Energy Code's solar requirement, and the panels can be placed on the ADU or on the main house.1

If you use a preapproved plan, the application is subject to a 30-day review.1

Fees to expect

School fees apply to ADUs and JADUs.1 So does the city's General Plan Maintenance Fee.1 The bulletin points to a separate fee bulletin for the full list, which we haven't summarized here.

Our read

San Diego rewards a careful first hour of site research. Whether your lot is in the Coastal Overlay Zone or a Very High Fire Hazard Severity Zone decides which version of the rules you are reading, and both can be checked on the city's zoning portal before you pay for drawings.

Common questions

Can I build an ADU right on the property line in San Diego?

The city allows a new ADU to encroach into the side and rear setbacks up to the property line, unless the building code requires separation.1 A 4-foot setback applies above 16 feet next to residential property1 and in a Very High Fire Hazard Severity Zone.1 For how openings near a lot line are treated elsewhere, see Oakland's fire separation rules.

Can I use my San Diego ADU as a short-term rental?

An ADU may not be leased for a term of less than 31 consecutive days.1

Does an ADU in San Diego need solar panels?

A newly built detached ADU that is not a manufactured unit is subject to the Energy Code's solar requirement, and the panels can go on the ADU or the main house.1

Keep reading

About this page

Written by
The Lotline Editorial Team. Editorial policy
Where it comes from
We wrote this from material published by City of San Diego and California Legislative Information. You'll find each document, and the part we used, under References below.
How it was checked
Before publishing, we checked each statement against the original wording of its source. How we work
Last reviewed
. Rules and city procedures change, so confirm current requirements with your permitting agency.
Corrections
Email support@lotlinepermits.com. We check every report against the document and fix what is wrong.

References

  1. 1Information Bulletin 400: Accessory Dwelling Unit/Junior Accessory Dwelling Unit (January 2026)City of San Diego, Development Services Department. Read on November 10, 2026.Cited: ADU Setback Regulations, Construction of New Detached Structures; ADU Setback Regulations; Editor's Note; ADU Fire Sprinkler Systems; ADU Parking Regulations; ADU Size Regulations; Other Regulations; Preapproved ADU Plans; bulletin header; Building Permit Requirement; Number of Allowed ADUs; Front Yard Requirements; Coastal Development Permit Requirement; Sale or Conveyance of ADUs; JADU Agreement Required; How to Apply; Other Permit Requirements, Forms; ADU Solar Photovoltaic Systems; Fees.
  2. 2California Government Code, Title 7, Division 1, Chapter 13, Article 2 (Sections 66314 to 66331)California Legislative Information. Read on November 10, 2026.Cited: § 66314(d)(7); § 66314(d)(12); § 66314(d)(11).

General information, not legal advice. Read the disclaimer.