Everything homeowners ask about building an ADU in San Jose — answered with 2026 data.
Yes, ADUs are allowed in Any zoning district where the lot has a legally permitted single-family, duplex or multifamily dwelling (SJMC 20.80.175 A; ADU Universal Checklist, Bulletin #210 rev. Sept 16, 2026, Part 1). An open Code Enforcement case must be closed before plans are accepted. Flood zones A/AE/AH/AO, geohazard, landslide or liquefaction zones, Historic Resources Inventory listing and Wildland-Urban Interface areas add design rules or clearances rather than prohibiting the unit. in San Jose, CA. The maximum size for a detached ADU is Two tracks that cannot be mixed. City standards (SJMC 20.80.175 D.1, Table 20-55): 1,000 sq ft on lots up to 9,000 sq ft, 1,200 sq ft on larger lots, and no cap when converting an existing detached accessory structure. State standards (SJMC 20.80.176 / Gov. Code 66323): 800 sq ft. Minimum 150 sq ft on either track. Square footage is livable floor space measured to the exterior finish; a covered porch or balcony more than 50% enclosed counts (20.80.175 E.3). Attached ADUs can be up to City standards: up to 50% of the existing primary dwelling's living area, capped at 1,000 sq ft on lots up to 9,000 sq ft and 1,200 sq ft on larger lots. San Jose has an ADU-friendliness score of 8/10. Check our full San Jose ADU rules page for complete zoning details.
ADU construction in San Jose typically costs $200,000-$450,000. The cost per square foot averages $300-$500. Garage conversions are more affordable at $90,000-$150,000, while prefab ADUs cost $150,000-$300,000. Permit fees add FY 2026-27 Building Fee Schedule (effective Aug 10, 2026): ADU 0-750 sq ft $422 issuance + $1,137 plan review + $1,732 inspection = $3,291; 751-1,200 sq ft $633 + $1,950 + $2,520 = $5,103. Excludes construction taxes, school and parkland fees and any planner meeting ($398/hour). to your budget. See our detailed San Jose ADU cost guide.
Detached ADUs in San Jose can be up to Two tracks that cannot be mixed. City standards. Attached ADUs are limited to City standards: up to 50% of the existing primary dwelling's living area, capped at 1,000 sq ft on lots up to 9,000 sq ft and 1,200 sq ft on larger lots. Junior ADUs (JADUs) have a cap of 500 sq ft maximum, 150 sq ft minimum, inside the walls of an existing or proposed single-family home (an attached garage counts). Since Ordinance 31329 (effective July 16, 2026) SJMC 20.80.178 applies Gov. Code 66333 directly: an efficiency kitchen is required, the bathroom may be shared, rentals must be 30 days or longer, and a deed restriction (Form 313, wet-signed for the County Recorder) is recorded. One JADU plus one ADU is allowed per single-family lot (20.80.175 B.1). Maximum height is City standards (SJMC 20.80.175 D.2): detached one-story 18 ft; detached two-story 25 ft to the roof; attached 25 ft; two stories maximum; 25 ft on duplex/multifamily lots. State standards (Gov. Code 66321(b)(4); Bulletin #210): detached 16 ft, plus 2 ft for a pitched roof within a half-mile walk of a major transit stop or high-quality transit corridor; attached 25 ft; detached on a multifamily lot 18 ft plus 2 ft roof pitch. Roof height is measured per SJMC 20.200.510. You are allowed up to Single-family lot: 1 ADU on a qualifying lot.
Rear setback: City standards: 0 ft for a one-story detached ADU; 4 ft, with eaves of 1 ft or less, for any second story (SJMC 20.80.175 D.3). State standards: 4 ft. A structure converted to an ADU keeps its existing setback; Building and Fire Code separations and easements still apply. City-track detached units must sit at least 6 ft from the main home and, with other accessory structures, cover no more than 40% of the rear yard, a cap that cannot block an 800 sq ft ADU with 4 ft setbacks (D.5.c, D.5.e). Side setback: City standards: 0 ft for the first story, 4 ft for a second story (SJMC 20.80.175 D.3.b and D.3.e; Bulletin #210 note 2 confirms zero is allowed subject to Building and Fire Code). State standards: 4 ft on both sides. Conversions keep their existing setbacks. Duplex and multifamily lots use the same figures. A new City-track detached ADU that keeps a 4 ft interior side setback may sit as close as 45 ft to the front property line (D.5.b). Front setback: The front setback of the zoning district (Title 20 Table 20-60, varies by district) under both tracks, except that it may be encroached if it would otherwise prevent an 800 sq ft ADU (SJMC 20.80.175 D.3.a; Bulletin #210 note 7). City-track detached ADUs must be in the rear yard or, with a 4 ft interior side setback, at least 45 ft back from the front property line (D.5.b); on Historic Resources Inventory lots the 45 ft rule always applies (E.1.c). State-track conversions: no front-setback rule. Note that garage conversions may be exempt from setback requirements if the existing structure is already within the setback area.
None. SJMC 20.80.175 I requires no off-street parking for an ADU and no replacement of covered parking removed to build it; Bulletin #210 (rev. Sept 16, 2026) lists parking as 'None' under both the City and the State standards for single-family, duplex and multifamily lots. Many cities and states have been relaxing ADU parking requirements in recent years. In California, no additional parking is required for ADUs near transit.
Not required for an ADU: the owner signs Form 312 (a declaration, not an occupancy covenant) and SJMC 20.80.175 F says a later sale or rental does not affect the unit's legal status. For a JADU, owner-occupancy of the main home is required only if the JADU shares sanitation facilities with it (Gov. Code 66333(b), as amended by AB 1154 and applied by SJMC 20.80.178 since July 2026); a JADU with its own bathroom has none. A Form 313 deed restriction is recorded for every JADU. Note that owner-occupancy rules vary by state law — California and several other states have eliminated this requirement for standard ADUs.
The ADU permit review timeline in San Jose is typically City-published: the first round of building review typically takes 20 business days and complete plans stay within one or two cycles (ADU FAQs); preapproved plans can be issued the same day as the review meeting. Gov. Code 66317 (SB 543) deems the application approved after 60 days. Plan check: Electronic review in SJePlans in three phases: Prescreen (a permit specialist confirms the package is complete and invoices the initial plan review fee), Plan Review (comment and resubmittal cycles, all through SJePlans), and Issuance Review (residual plan review and inspection fees, taxes, school and parkland fees paid, then the permit card and stamped plans are released). Fire Prevention checks a 150 ft hose path along a 4 ft clear route, a hydrant within 600 ft and a 1,000 gpm at 20 psi flow letter from the water company; the missing letter is the city's most-cited cause of delay. Pre-approved plans availability: Yes. The Preapproved ADU program currently lists 7 city-reviewed standard plans from 5 vendors, 476-799 sq ft (1 bed/1 bath to 2 bed/2 bath); about 15 further plans from 7 vendors, 440-1,000 sq ft, are under review and not yet eligible. Applicants still submit a site-specific plan (siting, setbacks, utilities); a dedicated review team can issue the permit the same day as the plan review meeting when the site documents are complete (deferred structural submittals, clearances or variances take longer). Eligibility: a residential lot with an existing single-family home or duplex, outside geohazard, landslide, flood and Wildland-Urban Interface zones. Gov. Code 65852.27 governs pre-approved plan programs.
Average ADU rental income in San Jose: 1-bedroom units rent for $2,500-$3,000/month, 2-bedroom units for $3,100-$3,600/month. Short-term rentals: No for stays under 30 days: the city's ADU FAQs set a 30-day minimum rental term for an ADU (including Airbnb-type rentals) and Gov. Code 66333 bars short-term rental of a JADU. Longer rentals to anyone are allowed. Expected ROI: 8-12% gross annual yield on a new build ($3,300/mo on a $350,000 detached unit is about 11% before vacancy, tax and financing); a $120,000 garage conversion at $2,600/mo is nearer 25% gross.
The minimum lot size for an ADU in San Jose is No minimum lot size (the former 3,000 sq ft minimum was removed on December 17, 2019). Lot size only sets the City-track size cap (9,000 sq ft threshold, SJMC 20.80.175 D.1) and, on lots of half an acre or more, a 100 ft setback from any riparian corridor (D.5.f). The minimum ADU size is 150 sq ft (Bulletin #210). This applies to detached ADUs — garage conversions and JADUs may have different or no lot size requirements.
Garage conversions are one of the most popular and affordable ADU options. In San Jose, a garage conversion typically costs $90,000-$150,000. The key advantages are lower cost (no foundation work), potential setback exemptions, and faster permitting. Read our complete garage conversion guide.
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