Minimum ADU size
150 sq ft
Shown in the City’s 2026 Universal Checklist for the principal ADU paths.
San Jose ADU requirements · 2026
The most important San Jose rule is that City Development Standards and State Development Standards are separate paths. The correct path changes maximum size, setbacks, height and siting, so the address and project type must be reviewed before a model is treated as buildable.
Quick answers
Minimum ADU size
150 sq ft
Shown in the City’s 2026 Universal Checklist for the principal ADU paths.
City detached max
1,000–1,200 sq ft
City path varies at the 9,000 sq ft lot threshold.
State new ADU max
800 sq ft
The State Standards table shows 800 sq ft for a new attached or detached ADU.
Parking
None
The current checklist shows no ADU parking requirement under either principal path.
Detailed San Jose guide
01
For a single-family property using San José City Development Standards, the current Universal Checklist shows a detached ADU maximum of 1,000 square feet on lots at or below 9,000 square feet and 1,200 square feet on lots above 9,000 square feet.
Attached ADUs under the City path are also tied to the main home’s size and the maximums shown in the checklist. The property and project type should be verified before selecting a model.
02
The City table shows a first-story detached ADU side and rear setback of zero feet under City Standards, with four feet for a second story, while the State new-ADU path shows four-foot side and rear setbacks.
The table also distinguishes height and siting rules. Building and Fire Code requirements still apply even when the zoning table shows a reduced setback.
03
Under the City detached path, the checklist notes a maximum 40% rear-yard coverage by structures, excluding swimming pools, and a minimum six-foot separation between the detached ADU and the main home.
The City path also includes a siting rule behind the main home or behind the zoning district’s 45-foot front setback. The State path handles these issues differently and can allow front-setback encroachment when no other option enables a minimum 800-square-foot ADU.
04
Flood zones, geologic or seismic hazards, historic status, WUI conditions, easements and former-pool areas can introduce additional design requirements or agency review.
That is why a rules table should be used as an orientation tool—not as an automated entitlement decision for a particular parcel.
Primary sources
These City resources are the primary references for the local claims on this page. Recheck them before submitting or relying on a specific rule.
San Jose ADU FAQ
It depends on the chosen development-standard path, property type and lot size. Under the City detached path, the current checklist shows 1,000 sq ft on lots at or below 9,000 sq ft and 1,200 sq ft on larger lots. The State new-ADU path shows 800 sq ft.
The current checklist shows different setbacks by path. City detached ADUs can show zero-foot side and rear setbacks on the first story and four feet on the second story; the State new-ADU path shows four-foot side and rear setbacks. Building and Fire Code requirements still apply.
The current Universal Checklist shows no ADU parking requirement under the City or State standards tables shown for single-family properties.
No. San José explicitly says the City and State development standards cannot be mixed; applicants must choose one complete standards path.
San Jose topic cluster
Property-specific next step
Start with the address, identify the unknowns, compare the closest model, and then define the design, permit and construction scope.