You have a garage that no longer holds a car, and a plan to turn it into a rental. The first architect you call says the permit is ministerial and should be quick. The second says the Rent Board has to weigh in first and it could take months. Both are describing San Francisco, and both are right — they are describing two different programs.
Short answer: San Francisco runs two separate accessory dwelling unit programs. The state-mandated program approves qualifying units ministerially — a detached new one may be up to 800 square feet with four-foot side and rear setbacks, and no parking is required (207.2). The local program has no size ceiling of its own and lets buildings with more than four units add an unlimited number, but it adds tenant-protection review (207.1).
Key numbers
| What | The number | Where it comes from |
|---|---|---|
| Detached new unit, state route | Up to 800 square feet | 207.2 |
| Side and rear setback, state route | At least 4 feet | 207.2 |
| Parking required, state route | None | 207.2 |
| Units allowed, local route, buildings of four units or fewer | One | 207.1 |
| Units allowed, local route, buildings over four units | No limit | 207.1 |
| Conversion inside an existing multi-unit building | Up to 25 percent of existing units, and at least one | 207.2 |
| Size a city may never cap below | 850 square feet, or 1,000 with more than one bedroom | 66321 |
Two programs, not one
An accessory dwelling unit — a second, self-contained home on a lot that already has housing — is normally counted against the number of homes a lot is allowed. Both San Francisco programs exist to switch that counting off. The state-mandated program says so plainly:
Adding an ADU or JADU in compliance with this Section 207.2 does not exceed the allowable density for the lot.
The programs are not a menu you pick from at leisure. The code sorts you: if a project does not meet the state-mandated program's requirements, it is regulated under the local program instead (207.2). So the practical question is whether your project fits the state route, and what you gain or lose if it does not.
The state route: fixed shapes, fast approval
The state-mandated program approves a defined set of project shapes, each with its own conditions (207.2):
- Inside an existing house or accessory structure. The unit sits within existing or proposed space, with its own separate entrance. If an existing accessory structure needs to grow to fit a doorway, the addition is capped at 150 square feet, and only to accommodate getting in and out.
- A detached, newly built unit. At least four feet from the side and rear lot lines, no more than 800 square feet of gross floor area, and within the applicable height limit.
- Conversion inside an existing multi-unit building. Units carved out of space that is not livable today — storage rooms, boiler rooms, passageways, attics, basements, garages. The total may not exceed 25 percent of the primary units already in the building, and every such building is allowed at least one.
- Detached units on a multi-unit lot. No more than two per lot, again at four feet from side and rear lines.
Two features of this route matter more than the numbers. No parking is required for the unit. And for a designated historic property or one inside a historic or conservation district, the project must meet objective architectural review standards, but it does not need a Certificate of Appropriateness or a Permit to Alter (207.2) — normally the slowest step on a historic building.
The local route: bigger buildings, more units
The local program is where San Francisco is genuinely more generous than the state floor, and it turns on how many homes the lot already has (207.1):
- Four existing units or fewer — or zoning that would permit four or fewer — allows one unit.
- More than four existing units, zoning permitting more than four, or a building undergoing seismic retrofitting: no limit on the number of units, as long as all other health and safety requirements are met.
The trade is where the unit may go. Under the local program it must be built entirely within the buildable area of the existing lot with no vertical addition, or inside the built envelope of an existing, authorized detached garage, storage structure, or similar building (207.1). The code fixes that envelope as it existed on July 11, 2016, so a shed enlarged since then does not enlarge your options.
The tenant rules that stop local-program projects
This is the part the first architect forgot. Under the local program the Planning Department shall not approve an application where a tenant on the lot was evicted under specified provisions of the Administrative Code — within 10 years before the permit application for some grounds, and within 5 years for another (207.1). There are narrow exceptions where a temporarily displaced tenant moved back, or declined a documented offer to.
Before applying, the owner must file a declaration with the Rent Board, signed under penalty of perjury, describing any housing services attached to the part of the property where the unit would go and whether the project would cut them off. Tenants may contest it by petitioning within 30 calendar days of the required notice, and the Rent Board aims to return a determination within 90 calendar days (207.1). The Planning Department cannot approve the project until that comes back clean.
"Housing services" is broader than most owners expect — storage, laundry and parking areas are the usual candidates, because those are exactly the spaces a conversion consumes.
What state law guarantees underneath both
State law sets floors that a city may not undercut, and it is worth knowing them as a check on any local answer. A city may not cap an accessory unit below 850 square feet, or below 1,000 square feet where it has more than one bedroom, and may not impose a minimum lot size (66321). Lot coverage, floor area, open space and front setback rules may not be applied in a way that prevents an 800 square foot unit with four-foot side and rear setbacks (66321). Detached units must be allowed to at least 16 feet, rising to 18 feet within half a mile of a major transit stop or high-quality transit corridor (66321).
These are ceilings on the city, not requirements on you. Nothing obliges you to build 800 square feet; the rule says San Francisco cannot write a standard that makes 800 impossible.
One more state rule shapes the exit: the unit may be rented separately from the main house, but may not be sold or conveyed separately from it (66314). Cities must also approve the qualifying categories ministerially — without discretionary review (66323).
San Francisco also runs a Housing Innovation Program in its Administrative Code. Its own definitions restrict it to an owner who has held the residence for at least five years before applying for assistance (85.2), so it is not a route for a recent buyer.
What this does not settle
Which program your project lands in depends on facts this cannot see: the zoning of your lot, how many homes it legally contains, whether anyone has been evicted from it, whether it is historic, and what your existing structures actually are. Height limits, exposure, open space and rear yard rules still apply and are not covered here. Building and Fire Code requirements apply in full under both routes (207.2). Confirm with San Francisco Planning and the Rent Board before you spend money on drawings; the San Francisco overview collects the rest of the local rules.
Sources
- San Francisco Planning Code 207.1 — local accessory dwelling unit program
- San Francisco Planning Code 207.2 — state-mandated accessory dwelling unit program
- Government Code 66314 — local accessory dwelling unit ordinances
- Government Code 66321 — size, setback and height limits a city may not impose
- Government Code 66323 — ministerial approval categories
- San Francisco Administrative Code 85.2 — Housing Innovation Program definitions
