Your architect sketches a rear addition, you love it, and then the planner's first comment lands: the addition sits in the required rear yard. You go looking for the setback number and cannot find one, because San Francisco does not use a fixed number. It uses a percentage of your lot's depth — which means the deeper your lot, the more of the back of it you have to leave open.
The short answer: in San Francisco's RH, RM-1, RM-2, RTO and RTO-M districts, the basic rear yard is 30% of the total depth of the lot, but never less than 15 feet. In the other districts covered by the rule, it is 25% of the total lot depth, again never less than 15 feet (§ 134).
Key numbers
| District group | Basic rear yard | Where it comes from |
|---|---|---|
| RH, RM-1, RM-2, RTO, RTO-M | 30% of total lot depth, minimum 15 feet | § 134(c)(1) |
| All other districts covered by the section | 25% of total lot depth, minimum 15 feet | § 134(c)(2) |
| NC-S districts | No rear yard required | § 134(b) |
| Lot coverage in C districts | 80% at residential levels (up to 100% in limited cases) | § 134(H) |
| Corner and through lots with two buildings | Total rear yard not less than 30% of depth or 15 feet, whichever is greater | § 134(f) |
| Reduction for a qualifying accessory unit | Down to 20% of depth, by Zoning Administrator action | § 134(f) |
How the percentage works
the basic rear yard shall be equal to 30% of the total depth of the lot on which the building is situated
The measurement is off total lot depth, not off the building. On a 100-foot RH lot, 30% is 30 feet of required rear yard; on a 75-foot lot, 22.5 feet. On a shallow 45-foot lot, 30% is 13.5 feet — below the floor, so the 15-foot minimum takes over and protects small lots from being consumed by the percentage.
The 25% figure applies in the other districts the section covers, with the same 15-foot floor.
Two districts sit outside the calculation entirely: NC-S districts require no rear yard, and where these provisions conflict with a Special Use District or a Residential Character District, the provisions of that district control instead (§ 134(b)). Before you calculate anything, check whether your parcel sits in one of those overlays.
Which floors the rear yard applies to
This is the part that surprises homeowners: a rear yard is not only a ground-level thing. Section 134(d) sorts districts into groups by which stories must be kept clear:
- RH, RM, RTO, NC-1, NCT-1 and a list of named commercial districts including Inner Sunset, Cole Valley, Haight Street, Sacramento Street, 24th Street-Noe Valley and West Portal Avenue — the rear yard is provided at grade level and at each succeeding level or story of the building. Nothing may project back into it at any floor.
- NC-2, NCT-2 and a long list of named districts including Castro Street, Valencia Street, Irving Street, Noriega Street, North Beach and Glen Park — the rear yard is provided at the second story and each succeeding story, and at the first story if that story contains a dwelling unit.
- RC-3, RC-4, NC-3, NCT-3, Hayes-Gough, Japantown, Polk Street, SoMa NCT, Mission Street and the M, SPD, MUR, MUG, MUO and UMU districts — the rear yard is provided at the lowest story containing a dwelling unit, and at each succeeding level.
- Upper Market Street NCT — at grade level and each succeeding story. For buildings there with no residential use that do not abut lots with an existing pattern of rear yards or mid-block open space, the Zoning Administrator may waive or reduce the requirement.
- RED, RED-MX and WMUG — at ground level for any building containing a dwelling unit, and at each succeeding level.
The pattern is deliberate: in residential districts the open space is protected from the dirt up, while in mixed-use districts ground-floor commercial may fill the lot and protection starts where people live.
What the yard is for, and what may sit in it
The section states its own purposes (§ 134(a)): assuring the protection and continuation of established mid-block landscaped open spaces; maintaining a scale of development appropriate to each district; providing natural light and ventilation to residences, work spaces and adjacent rear yards; and giving residents usable open space and views into green rear-yard space.
That first purpose explains why the rule is a percentage: every lot leaving the same proportion open at the back produces one continuous green space through the middle of the block, which is the thing being protected — more than any individual backyard.
Because of that, the rear yard is not free space to build in. Only those obstructions specified in Section 136 of the Planning Code are permitted in a required rear yard, and no other obstruction may be constructed, placed or maintained there. Motor vehicles, trailers and boats may not be parked or stored in it except as Section 136 allows (§ 134(e)). Section 136 is a separate list this article does not reproduce — read it before you plan a shed, a deck or a parking pad.
Corner lots, through lots, and the accessory-unit reduction
Corner lots and lots at the intersection of a street and an alley at least 25 feet wide get a substitution: the required rear yard may be replaced with an open area equal to the basic requirement, at the same levels of the building (§ 134(h)). The open space still has to exist — it just does not have to be at the back.
A corner lot or a through lot in RH, RTO, RTO-M, RM-1 or RM-2 may hold two buildings, one fronting each end, with the required rear yard placed in the central portion of the lot between them. In that arrangement the total rear yard may not be reduced below 30% of the total lot depth or 15 feet, whichever is greater (§ 134(f)).
There is one path to go below that, and it exists to make accessory dwelling units possible: the Zoning Administrator may reduce the total depth to 20% under Section 307(l), solely for the purpose of constructing an accessory dwelling unit under Section 207.1, and only where the property owner enters a Regulatory Agreement subjecting the ADU to the San Francisco Rent Stabilization and Arbitration Ordinance. It is a trade: less open space in exchange for a rent-controlled unit.
In C districts, the section swaps the rear yard for a lot coverage cap — 80% at all levels containing residential uses, rising to as much as 100% on levels holding only lobbies and circulation, or where all residential uses including circulation are within 40 horizontal feet of a property line fronting a street or alley. The unbuilt portion must be open to the sky except for obstructions permitted under Section 136(c), and where adjacent properties have an existing rear yard the new project's unbuilt area must be designed to adjoin it. Commercial-to-residential adaptive reuse projects are exempt from the lot coverage requirement (§ 134(H)). In C-3 districts, an exception to the rear yard requirement may be allowed through the Section 309 review process — the procedure governing construction and substantial alteration in C-3 districts, and the granting of exceptions to certain Planning Code requirements — provided the building's location and configuration assure adequate light and air.
Before you draw anything
Rear yard is local zoning, not statewide building code — this is San Francisco's own rule, and it is stricter than anything the state requires. Three things to confirm for your specific parcel: your zoning district, your total lot depth, and whether any Special Use District or Residential Character District overlays your block and displaces these provisions. San Francisco's planning department maintains published interpretations of this section, and the code notes their existence directly. Our San Francisco overview collects the city's other regulatory requirements alongside this one.
