San Diego ADU rules
and requirements.
San Diego rewrote its granny flat rules repeatedly between 2020 and 2026, and most of what you will read online was written somewhere in the middle of that. Here is where it stands today, with the numbers first and the dates on everything.
Reviewed 12 October 2026 · re-check quarterly
| Rule | Where it stands in 2026 |
|---|---|
| Maximum size, detached | 1,200 sq ft |
| Stories | Two permitted |
| Side and rear setbacks | 4 ft. Often none at all under 16 ft in height, outside fire hazard zones |
| Parking | None required within half a mile of transit. Otherwise one off-street space |
| Owner occupancy, ADU | Not required. Rent it out and live elsewhere |
| Owner occupancy, JADU | Only where the JADU shares a bathroom with the house — changed January 2026 |
| Junior ADU size | 500 sq ft maximum, inside the existing or proposed house, own entrance |
| Impact fees | None at or under 750 sq ft. Proportional above it. JADUs exempt entirely |
| School fees | Exempt at or under 500 sq ft |
| Minimum rental term | 30 days. JADUs cannot be short-term rentals at all |
Sources are linked at the foot of this page. Anything parcel-specific — fees, coastal status, fire zone — is flagged below rather than guessed at.
The four things that actually decide your project
Most of the table above is settled statewide and will not surprise you. Four items are local, and they are the ones that move timelines and budgets. In rough order of how often they catch people out:
1. Whether you are in the Coastal Overlay
If your lot sits in the Coastal Overlay Zone and the ADU is detached, assume you need a Coastal Development Permit. You will read in a lot of places that you are exempt beyond fifty feet from the bluff — that threshold belongs to the general improvements exemption, and the municipal code carves ADUs out of that exemption specifically. Any ADU not completely contained inside the existing house is ineligible.
The overlay is drawn parcel by parcel, not by neighbourhood, so the only way to know is to check your address against the city map. La Jolla, Pacific Beach and Ocean Beach are largely in it. Budget the time, not just the fee.
2. Whether you are in a very high fire hazard severity zone
In a VHFHSZ the building has to meet wildland-urban interface standards, the four-foot side and rear setback applies regardless of height, and units built under the bonus programme need sprinklers. All of it is buildable. It costs more, and it is better to know before you fall for a plan than after.
3. Where your ADU lands against 750 sq ft
This is the single sharpest line in San Diego ADU economics. At or under 750 sq ft, no development impact fees. Above it, fees are charged in proportion to the size of the primary dwelling — which means the same ADU costs a different amount in fees depending on how big your main house is.
We will not print a fee figure, because San Diego does not publish a flat one; it comes out of the city's parcel-specific calculator. Treat any site quoting you a confident dollar amount with suspicion. It is also a real part of why the CADU 500 is priced where it is.
4. Whether you want a JADU or an ADU
A junior ADU is a conversion inside the existing house — 500 sq ft maximum, its own entrance, and it can share a bathroom with the main house. It is cheaper. It also carries restrictions a detached unit does not, and those changed this year.
What changed in 2026
Three changes took effect that most ADU pages still have not caught up with. If something you read elsewhere contradicts these, check its date.
AB 1154 — junior ADUs, effective January 2026
Two changes, and the first is the one people care about. Owner-occupancy now applies only where the JADU shares a bathroom with the main house. Give the JADU its own bathroom and there is no owner-occupancy requirement at all — you can rent both the house and the JADU and live somewhere else entirely. That was not true before.
The second: JADUs cannot be used as short-term rentals. Thirty consecutive days minimum, statewide, regardless of what the local short-term rental ordinance says.
SB 1211 — multifamily lots
Detached ADU capacity on lots with existing multifamily housing went from two units to as many as eight, capped at the number of existing units on the lot. Irrelevant if you own a single-family home; decisive if you own a fourplex.
AB 2533 — unpermitted units built before 2020
If there is already an unpermitted granny flat on your property and it went up before 1 January 2020, a local agency can no longer refuse to permit it purely because it was unpermitted, absent a genuine safety problem. Impact and connection fees are waived unless new infrastructure is actually required, and there is a confidential third-party inspection route so you can find out where you stand before you file anything.
That last provision matters more than it sounds. The reason these units stay unpermitted for decades is that the owner cannot risk asking the question. Now you can ask it privately.
What a web page cannot tell you
Your setback, your fee, your coastal status and your fire zone are all properties of your parcel, not of San Diego. Everything above is the framework; none of it is a determination about your lot. We find out the real answers during the site walk and put them in writing, and until somebody has stood on your property any builder telling you exactly what you can build is guessing.
We are also not land use attorneys. For anything contested — a disputed overlay boundary, an easement, a non-conforming structure — get one.
Know the rules, now price the build. Pick a plan, choose a level for each finish, and watch the figure move.
Open the studioSources
- San Diego ADU rules — sizes, setbacks, fees
- San Diego ADU guide 2026 — process and costs
- San Diego County ADU requirements
- AB 1154 — JADU owner-occupancy changes for 2026
- California ADU laws 2026 — AB 1154, SB 1211, AB 2533
- San Diego Municipal Code §126.0704(a)(9) — coastal exemption carve-out
- California SB 13 — impact fee exemption under 750 sq ft