Permit fees
Size-dependent
San José directs applicants to its fee estimator and current fee schedule.
San Jose ADU cost · 2026
A useful San Jose ADU budget separates the building itself from design, engineering, permitting, utility work, site conditions, owner selections, and contingency. The right number starts with the property and the scope—not a statewide price-per-square-foot slogan.
Quick answers
Permit fees
Size-dependent
San José directs applicants to its fee estimator and current fee schedule.
School impact fee
No fee under 750 sq ft
The City FAQ states school impact fees do not apply to ADUs smaller than 750 sq ft.
Biggest variable
Property conditions
Access, utilities, slope, fire review, demolition, foundation, and finishes can materially change cost.
Best next step
Address-first estimate
Use the actual San Jose property before treating a planning range as project-specific.
Current ADU.zone planning ranges
These are preliminary ADU.zone ranges using current calculator assumptions for San Jose, standard finishes, steel framing, and no property-specific difficult-site or utility adders. They are not bids.
600 sq ft · 1 bedroom
$306,000–$410,000
Baseline planning range before property-specific utility, access, hazard, demolition, foundation, finish and agency adjustments.
750 sq ft · 2 bedrooms
$388,500–$521,500
Baseline planning range before property-specific utility, access, hazard, demolition, foundation, finish and agency adjustments.
1,000 sq ft · 2 bedrooms
$529,000–$710,000
Baseline planning range before property-specific utility, access, hazard, demolition, foundation, finish and agency adjustments.
Detailed San Jose guide
01
A complete planning budget should distinguish base construction from architecture, structural and civil engineering, Title 24 and CalGreen work, permit and agency fees, utility upgrades, site work, demolition, drainage, foundation conditions, finishes, appliances, solar or electrification scope, and contingency.
Two ADUs with the same square footage can price very differently when one has straightforward access and existing utility capacity while the other needs long utility runs, electrical-service work, fire-related measures, retaining or drainage work, or premium interior selections.
02
San José publishes a Building Fee Estimator and a current fee schedule. Permit, plan-review and inspection fees are only one layer of the overall ADU budget, and other charges can apply depending on the project.
Use City fee tools for permitting costs and use a property-specific construction estimate for the build. Combining them into one unsupported “permit cost” number can create a misleading budget.
03
San José requires ADU applicants to address fire-flow information and directs applicants to obtain a water-company letter with hydrant flow data. Electrical service, sewer routing, water service, trenching and meter strategy can also affect scope.
Those items should be investigated before a final contract price is treated as fixed. A preliminary calculator is useful for planning; a construction proposal should follow site and utility investigation.
04
Smaller ADUs are not always proportionally cheaper because kitchens, bathrooms, utility connections, design, permitting and mobilization are partly fixed costs. Larger ADUs add framing, finishes and systems, but some fixed costs are spread across more square footage.
Compare the smallest model that satisfies the use case, then verify whether the property supports that footprint before spending time optimizing finishes.
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
There is no single reliable citywide number. Size, site conditions, utilities, design, finish level, access, fire requirements, foundation conditions and current trade pricing all matter. ADU.zone provides preliminary model ranges, then refines them around the actual property.
That depends on the proposal. Permit and agency fees should be stated clearly as included, excluded, allowances or owner-paid items. San José publishes its own fee estimator and current fee schedules.
Long sewer or water runs, electrical-service upgrades, trenching, meter work, fire-flow conditions and difficult access can add scope that is not visible from ADU square footage alone.
A final price is stronger after the design team has investigated the property, utility path, access, applicable rules and major site conditions. Early ranges should be labeled as planning estimates.
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.