Everything homeowners ask about building an ADU in San Jose — answered with 2026 data.
Yes, ADUs are allowed in Any zoning district where the site has a legally-built, permitted main residence - single-family, duplex or multifamily. Not restricted to the named residential districts, so listing R-1/R-2/R-M/R-MH understates where ADUs are allowed. Practical gating is by property condition rather than zone: an active Code Enforcement case must be resolved before plans are accepted, and flood, geohazard/liquefaction/landslide, historic and Wildland-Urban Interface designations add design requirements or clearances rather than prohibiting the ADU. in San Jose, CA. The maximum size for a detached ADU is Depends on which standards track the applicant chooses. CITY Development Standards (SJMC 20.80.175): 1,000 sq ft on lots under 9,000 sq ft; 1,200 sq ft on lots over 9,000 sq ft. STATE Development Standards (SJMC 20.80.176): 800 sq ft on any lot. Minimum size 150 sq ft under either track. The tracks cannot be mixed. Same size table applies on duplex/multifamily lots under the City track.. Attached ADUs can be up to CITY Development Standards: up to 50% of the existing primary dwelling living area, capped at 1,000 sq ft on lots under 9,000 sq ft and 1,200 sq ft on lots over 9,000 sq ft. STATE Development Standards: 800 sq ft. Minimum 150 sq ft. Under the State track an attached ADU is prohibited if there is an existing or proposed conversion ADU. City track also requires the attached ADU's front door to be on a different facade from the main home. Note the 50% cap cannot be applied to force an ADU below the state floors in Gov. Code 66321. 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 $180,000-$400,000. The cost per square foot averages $250-$450. Garage conversions are more affordable at $100,000-$220,000, while prefab ADUs cost $130,000-$300,000. Permit fees add City building permit fees, FY 2026-27 Building and Structure Permits Fee Schedule, effective August 10, 2026. ADU 0-750 sq ft: permit issuance $422, plan review $1,137, inspection $1,732 (total $3,291). ADU 751-1,200 sq ft: permit issuance $633, plan review $1,950, inspection $2,520 (total $5,103). Permit issuance includes addressing assignment for the unit; inspection includes the meter release inspection. Modular fees are 10% lower for plan review and 20% lower for inspections. Separately, an optional preliminary virtual meeting with a planner is billed at the Planning Division's hourly rate of $398/hour with a 30-minute minimum (i.e. $199). These are city permit fees only and exclude school/parkland impact fees, construction taxes, and construction cost. to your budget. See our detailed San Jose ADU cost guide.
Detached ADUs in San Jose can be up to Depends on which standards track the applicant chooses. CITY Development Standards. Attached ADUs are limited to CITY Development Standards: up to 50% of the existing primary dwelling living area, capped at 1,000 sq ft on lots under 9,000 sq ft and 1,200 sq ft on lots over 9,000 sq ft. STATE Development Standards: 800 sq ft. Minimum 150 sq ft. Under the State track an attached ADU is prohibited if there is an existing or proposed conversion ADU. City track also requires the attached ADU's front door to be on a different facade from the main home. Note the 50% cap cannot be applied to force an ADU below the state floors in Gov. Code 66321. Junior ADUs (JADUs) have a cap of 500 sq ft maximum, 150 sq ft minimum. Must be built within the existing footprint of a single-family home (including converting an attached garage) or within a proposed new single-family residence, and must comply with SJMC 20.80.178. Same 500 sq ft cap under both the City and State tracks.. Maximum height is CITY Development Standards, single-family lot: detached ADU 18 ft for a first story, 25 ft for a second story; attached ADU 25 ft; maximum 2 stories either way. CITY standards on duplex/multifamily lots: 25 ft detached and 25 ft attached, maximum 2 stories. STATE Development Standards: attached 25 ft, detached 18 ft, plus up to 2 additional feet to accommodate a pitched roof; on duplex/multifamily 18 ft (+2 ft pitch). Our current '24 ft' is wrong and the '16 ft if a JADU already exists' clause does not appear in the city's standards at all.. You are allowed up to Single-family property: 1 ADU on a qualifying lot.
Rear setback: CITY Development Standards, detached ADU: 0 ft for the first story, 4 ft for a second story. STATE Development Standards: 4 ft. On duplex/multifamily lots the City track is 0 ft first story / 4 ft second story detached and 0 ft attached. Conversions of existing structures have no rear setback requirement under the State track. City-track detached ADUs must also keep a minimum 6 ft separation from the main home and must not cover more than 40% of the rear yard.. Side setback: CITY Development Standards, detached ADU: 0 ft for the first story, 4 ft for a second story. STATE Development Standards: 4 ft. Attached ADUs and JADUs under the City track have no stated side setback beyond meeting minimum Building and Fire Codes. On duplex/multifamily lots the City track is 0 ft first story / 4 ft second story detached, 0 ft attached.. Front setback: Per Table 20-60 of the zoning code, which varies by zoning district, under both the City and State tracks. Under the State track the front setback may be encroached if no other option enables a minimum 800 sq ft ADU on the site. Under the City track a detached ADU must additionally be sited behind the main home or at least 45 ft back from the front, whichever the zoning district requires. Conversions have no front setback requirement under the State track. The specific per-zone figures in Table 20-60 could not be read (see confidence note).. Note that garage conversions may be exempt from setback requirements if the existing structure is already within the setback area.
None. The city states 'None' for parking under both the City and the State development standards, on single-family, duplex and multifamily properties alike. Replacement parking is not required when a garage or carport is converted to an ADU.. 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. For a JADU, owner-occupancy of the main home is required ONLY where the JADU does not have its own sanitation facilities; a JADU with its own bathroom carries no owner-occupancy requirement. Where it applies, it is secured by a recorded deed restriction (Form 313 JADU Deed Restriction Agreement, which the County Recorder requires to be wet-signed). ADU applicants must separately sign Form 312 ADU Property Owner Declaration - a declaration, not an occupancy requirement. Rentals of under 30 days are not permitted for either.. 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 The city's own published figure is that the first round of building review typically takes 20 business days, with complete and accurate plans staying within one or two review cycles. Preapproved-plan projects may receive same-day permit issuance at the scheduled plan review meeting. The 60-day figure in our record is the state ministerial deadline (Gov. Code Chapter 13 / SB 543), not a San José-published processing time, and should not be presented as a city fact. The city flags the missing water-company flow letter as a main cause of delay.. Plan check: Standard review process. Pre-approved plans availability: Yes - a well-developed Preapproved ADU program, described by the city as the fastest and lowest-cost permit path, supported by a dedicated City review team. 6 preapproved plans from 4 vendors are currently available: Acsiom Designs (749 sq ft, 2bd/2ba); Ca2Homes (499 sq ft 2bd/1ba, 747 sq ft 2bd/2ba); J. Kretschmer Architect (748 sq ft 2bd/1ba, 476 sq ft 1bd/1ba); LiveLarge (795 sq ft 2bd/2ba). Permits may be issued the same day as the scheduled plan review meeting when site-specific documents are accurate and complete (exception: deferred structural submittals, clearances or variances take longer). Eligibility: lot must be zoned residential with an existing single-family home or duplex, and must NOT be in a geohazard, landslide, flood or Wildland-Urban Interface zone. Applicants still submit site-specific plans showing siting, utility connections and setbacks. A further 7 vendors have plans under review (including 800 and 1,000 sq ft options) that are NOT yet eligible for expedited review..
Average ADU rental income in San Jose: 1-bedroom units rent for $2,000-$2,800/month, 2-bedroom units for $2,500-$3,500/month. Short-term rentals: Restricted; requires transient occupancy tax registration. Expected ROI: 5-9% annual return.
The minimum lot size for an ADU in San Jose is No minimum lot size (the former 3,000 sq ft minimum was removed effective January 1, 2020). Note the city does impose a minimum ADU SIZE of 150 sq ft under both the City and State tracks, which is a genuine local standard our record does not carry.. 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 $100,000-$220,000. 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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