Permitting · 9 min read · May 25, 2026 · 355 words
San Jose ADU cost and permits: the fastest Bay Area permit cycle
San Jose issues detached ADU permits in 10–14 weeks — the fastest in the Bay Area — and operates one of California's largest pre-approved master plan libraries. Costs run $325K–$420K for a typical 800 sq ft build.
Key takeaways
- Garage conversion (400–500 sq ft) — $145K–$210K
- Junior ADU within main home (500 sq ft max) — $120K–$175K
- Attached ADU (600 sq ft) — $235K–$305K
Answered in this guide
Jump straight to the question you came in with — every answer is on this page, with links onward to the deeper guide.
- What is SB-9 and does it apply to me?
- What about hillside or coastal lots?
- I'm in an HPOZ — can I still build?
- Do you handle the permitting?
- What setbacks and height limits apply?
- How long does an ADU project take in Los Angeles?
More across the studio · the full FAQ map · the reference desk
San Jose has positioned itself as the most ADU-friendly large city in California. The Planning, Building and Code Enforcement department operates a true ministerial review, a same-day counter-permit option for pre-approved plans, and the largest municipal pre-approved master plan library in the Bay Area. The result: average permit issuance in 10–14 weeks, with master-plan projects clearing in 4–6 weeks.
The pre-approved master plan library
San Jose maintains 30+ pre-approved ADU plans from licensed firms covering studio through 1,200 sq ft configurations. Plans are public and free to view. Choosing a master plan skips architectural review entirely — your permit application moves to building plan check on day one. For most homeowners building a standard 600–800 sq ft detached unit, this is the highest-ROI decision of the entire project.
Cost ranges by configuration
- Garage conversion (400–500 sq ft) — $145K–$210K
- Junior ADU within main home (500 sq ft max) — $120K–$175K
- Attached ADU (600 sq ft) — $235K–$305K
- Detached ADU (800 sq ft, master plan) — $325K–$390K
- Detached ADU (800 sq ft, custom design) — $365K–$445K
Fees and connection costs
San Jose impact fees are waived on ADUs under 750 sq ft per state law. School district fees apply to units over 500 sq ft. San Jose Water Company connection runs $4K–$8K. PG&E electrical service upgrades, when required, run $7K–$15K. Total soft permit cost typically lands at $11K–$22K — meaningfully lower than San Francisco.
Willow Glen, Almaden, and Evergreen variance
Cost varies less by neighborhood in San Jose than in SF or LA. Willow Glen lots often have setback constraints from mature trees. Almaden Valley hillside lots may trigger geotechnical reports. Evergreen and Berryessa are typically the most cost-efficient — flat lots, good street access, simple utility runs.
Rental income reality
San Jose ADU rents in 2026 average $2,550/month for a 1-bedroom and $3,250/month for a 2-bedroom. Demand is strongest near Diridon Station, SAP Center, and the North San Jose tech corridor where Apple, Cisco, and Samsung campuses concentrate. Mid-term rentals targeting traveling tech contractors clear $3,400–$4,100/month at 70%+ occupancy.
Sources
- San Jose ADU master plans · City of San Jose
- Santa Clara County Assessor · Santa Clara County
Next chapter · 01 of 02
Cost · 10 min read
Peninsula ADU cost: Palo Alto, Menlo Park, Los Altos, Cupertino
Up the Peninsula, Palo Alto and Menlo Park flip the cost equation — same square footage, double the budget.
Detached ADUs on the Peninsula run $445K–$620K. Premium land, premium finishes, and the strictest design review process in the Bay Area set the floor.
FAQ · Permitting
Common questions on permitting
The questions readers send us most after this guide.
What is SB-9 and does it apply to me?
SB-9 (the California HOME Act) lets eligible single-family lots split into two parcels and/or add a duplex. We assess eligibility during the feasibility call — roughly 60% of LA single-family lots qualify on paper, fewer in practice once HPOZ, hillside, and coastal overlays are applied. SB-9 projects can stack with an ADU for up to four units on what was a single-family lot.What about hillside or coastal lots?
Hillside requires a Methane District review (where applicable) plus a haul route plan if grading exceeds 1,000 cubic yards. Coastal Zone projects (anything west of Lincoln Blvd in Venice, for example) need a Coastal Development Permit on top of standard LADBS approval. Both are workable; both add 60–90 days.I'm in an HPOZ — can I still build?
Yes, but with design review. Historic Preservation Overlay Zones require Certificate of Appropriateness from the cultural heritage commission before permits issue. We've shepherded projects through Miracle Mile, West Adams, Whitley Heights, and Spaulding Square HPOZs. Add 8–12 weeks for the COA process.Do you handle the permitting?
Yes. We file with LADBS or your local building department, manage plan check, coordinate utility upgrades, schedule inspections, and deliver final sign-off. You don't visit the counter, we do.What setbacks and height limits apply?
Statewide ADU law (AB 68/881) overrides most local restrictions: 4-foot side and rear setbacks, 16-foot height for detached one-story, 18-foot for two-story within ½ mile of transit. Front setbacks follow the underlying zone. We model your envelope at the schematic stage.How long does an ADU project take in Los Angeles?
Most detached ADUs run 9–13 months from contract to certificate of occupancy. Garage conversions are typically 4–6 months. Permitting alone is usually 60–120 days at LADBS depending on whether we use a pre-approved standard plan or a custom design that needs full plan check.
Reference desk · Permitting
More answers from the California reference desk
City-specific questions pulled from our 5,000-answer FAQ corpus — every link opens a deeper desk page.
How long does a ADU permit take in San Francisco?
City of San Francisco Planning & Building runs plan check 150–240 days on a complete, code-conformant submittal for a ADU. First-cycle approvals depend on three things: a stamped structural set, a Title 24 energy report bound into the package, and a site plan with verified setbacks. Most slippage comes from missing one of those three on first submittal.Why do ADU permits get rejected in San Francisco?
In San Francisco, the five most common first-cycle corrections are: (1) Title 24 energy compliance not bound to the submittal, (2) site plan setback math off by inches, (3) structural calcs not stamped by a CA-licensed engineer, (4) utility load calculations missing for the panel upgrade, and (5) drainage/grading not addressed for impervious-surface adds. Fixing all five before submittal cuts 150–240 days off the schedule.Does state ADU law override San Francisco rules for my ADU?
For qualifying ADU and JADU scopes, California Government Code §65852.2 and §65852.22 preempt most local discretionary review — San Francisco cannot impose owner-occupancy requirements (banned by AB 976), most parking minimums near transit, or stylistic design review. Local jurisdictions still control building-code application, Title 24, utility connection, and impact fee schedules. Non-ADU scopes (full additions, remodels, hillside builds) remain fully under local control.Are pre-approved standard plans available in San Francisco for a ADU?
Where San Francisco has adopted a pre-approved standard ADU plan program, using one cuts plan check by 30–60 days and removes the structural review fee. For programs that exist (LADBS, San Jose, San Diego), the trade-off is that floor-plan changes void the pre-approval. Most owners are better off using a standard plan as a starting point and accepting the layout it ships with.How long does a garage conversion permit take in San Francisco?
City of San Francisco Planning & Building runs plan check 150–240 days on a complete, code-conformant submittal for a garage conversion. First-cycle approvals depend on three things: a stamped structural set, a Title 24 energy report bound into the package, and a site plan with verified setbacks. Most slippage comes from missing one of those three on first submittal.Why do garage conversion permits get rejected in San Francisco?
In San Francisco, the five most common first-cycle corrections are: (1) Title 24 energy compliance not bound to the submittal, (2) site plan setback math off by inches, (3) structural calcs not stamped by a CA-licensed engineer, (4) utility load calculations missing for the panel upgrade, and (5) drainage/grading not addressed for impervious-surface adds. Fixing all five before submittal cuts 150–240 days off the schedule.Does state ADU law override San Francisco rules for my garage conversion?
For qualifying ADU and JADU scopes, California Government Code §65852.2 and §65852.22 preempt most local discretionary review — San Francisco cannot impose owner-occupancy requirements (banned by AB 976), most parking minimums near transit, or stylistic design review. Local jurisdictions still control building-code application, Title 24, utility connection, and impact fee schedules. Non-ADU scopes (full additions, remodels, hillside builds) remain fully under local control.Are pre-approved standard plans available in San Francisco for a garage conversion?
Where San Francisco has adopted a pre-approved standard ADU plan program, using one cuts plan check by 30–60 days and removes the structural review fee. For programs that exist (LADBS, San Jose, San Diego), the trade-off is that floor-plan changes void the pre-approval. Most owners are better off using a standard plan as a starting point and accepting the layout it ships with.How long does a JADU permit take in San Francisco?
City of San Francisco Planning & Building runs plan check 150–240 days on a complete, code-conformant submittal for a JADU. First-cycle approvals depend on three things: a stamped structural set, a Title 24 energy report bound into the package, and a site plan with verified setbacks. Most slippage comes from missing one of those three on first submittal.
Sources & further reading
- California Government Code §65852.2 — statewide ADU framework (ministerial review, 60-day clock).
- LADBS — Accessory Dwelling Unit information bulletins and current permit fee schedule.
- HCD — California Department of Housing & Community Development, ADU handbook (2024 update).
- Internal data: 120++ ADU projects delivered across Los Angeles County, 2018–2025.
Continue your read · the editorial path
We chained these chapters in the order LA homeowners actually need them. Each one picks up where the last one left a question open.
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