San Diego County

A plain-language guide to ADUs in San Diego County

Q: How much does an ADU cost in San Diego?

Cost depends on size, type, site access, and utility work. The site calculator gives a planning range. The ADU cost guide and feasibility guide explain the categories. The calculator is not a bid.

Q: How long does an ADU project take in San Diego?

Design and permits come first, then construction. Review time depends on the jurisdiction and whether the application is complete.

A plain-language guide to ADU rules, permits, costs and financing in San Diego County.

Last reviewed June 29, 2026

San Diego ADU rules Cost guide

AI-generated illustration of a backyard ADU. Not a real project.

RulesCity, county, and state sources

PermitsWhat review usually covers

CostsPlanning ranges, not bids

Informational cost calculator

A planning range based on size, type, finish, site, and utility assumptions. It does not collect a name, email, or phone number. It is not a bid or a quote.

Last reviewed June 29, 2026. Read the ADU cost guide for what these categories usually include.

Approximate size (sq ft) Project type Finish level Site complexity Utility upgrade risk Bathrooms

The range adds hard costs, soft costs, sitework, a utility allowance, and contingency. It leaves out land value and financing. Actual prices depend on plans, soils, utility routes, and permit review.

Guides on this site

Detached ADUs

Backyard units that stand apart from the main house, including access, utilities, and setbacks.

Garage conversions

What has to change when an existing garage becomes a legal dwelling.

Attached ADUs

Additions that share a wall, floor, or roof with the primary home.

JADUs

Junior units created inside a single-family home, including the 500 square foot limit.

Permitting

How plan check, fees, and inspections differ by jurisdiction.

Financing

HELOCs, renovation mortgages, and other ways owners pay for the work.

A lot in the City of Carlsbad follows that city's coastal permit, fee schedule, and size rules. The ADU handbook is a short planning overview. This site does not design or build ADUs.

Common questions

How much does an ADU cost in San Diego?

Cost depends on size, type, site access, and utility work. Use the calculator for a planning range, then read the ADU cost guide and the feasibility guide.

How long does an ADU project take in San Diego?

Design and permits come first, then construction. The permitting guide explains why review time depends on the jurisdiction and the completeness of the plans.

Which ADU types does this guide cover?

The guides cover detached ADUs, garage conversions, attached ADUs, and JADUs.

Official sources

Confirm current rules on the agency site before you submit plans. This guide links to the pages below and summarizes them in plain language.

City of San Diego

Development Services publishes the city's ADU and JADU program page.

Open the city ADU page

San Diego County

Unincorporated communities use the county Planning and Development Services ADU page.

Open the county ADU page

California HCD

The state housing department handbook explains the statewide ADU statute.

Open the HCD handbook

Open the San Diego rules page