Custom ADU builder in San Jose
Plan a detached backyard ADU around your household, available space and finish preferences. Compare steel-frame ADU models with a custom floor plan before setting the construction scope.
San Jose · Santa Clara County
San Jose ADU builder & contractor
Design, permits, engineering and complete ADU construction for San Jose homeowners. Start with your property, compare the right City or State pathway, then move from plans and permitting through construction with one coordinated team.
Serving Willow Glen, Rose Garden, Cambrian, Almaden Valley, Evergreen, Berryessa and neighborhoods across San Jose. Check your address first so size, setbacks, model fit, permitting and budget start with the actual property.
Up to 1,200 SF
Detached ADU under qualifying San José City standards
0–4 FT
Side and rear setbacks vary by the applicable City or State path
18–25 FT
Height options depend on the selected standard and property conditions
Potential same-day
For qualifying preapproved projects with a complete site-specific package
San Jose property checker
What can you build on your San Jose property?
Start with the address. We organize the jurisdiction, lot-size context, City-versus-State pathway, likely size and setback questions, preapproved-plan fit, model options and next permit steps.
Property results are preliminary. Final feasibility, permits, utilities, pricing and timing depend on site-specific conditions, current City requirements and review by the appropriate licensed professionals.
Full-service ADU construction
Custom ADU builder & contractor services in San Jose
Start with a custom ADU builder or ADU contractor in San Jose, then coordinate design, architecture, engineering, permits, budgeting, construction, inspections, and handoff around the property.
San Jose ADU contractor
Bring site preparation, foundation work, framing, utilities and finishes into one written construction scope, with a clear inspection sequence and project-specific budget.
ADU design-build planning
Connect ADU design, engineering coordination, San Jose permits and construction planning. Start with the address so the layout and budget reflect the actual property.
Garage conversion ADUs
Compare a San Jose garage conversion with a new backyard cottage. Review the existing structure, foundation, ceiling height, moisture protection and utility connections before choosing a plan.
ADU plans & permit coordination
Explore one- and two-bedroom ADU floor plans, attached ADUs and preapproved-plan options. Coordinate the architect and engineer scope required for the site and City submittal.
Steel-frame backyard homes
Explore a steel-frame accessory dwelling unit for family living or a separate household. Plan privacy, storage, daylight and outdoor space alongside the permitted building footprint.
San Jose ADU builder & contractor resource · 2026
From San José property analysis to plans, permits, and construction.
This page combines current City of San José ADU rules with ADU California Inc. model, cost, financing, and property-review tools. The local rules below were checked against the City’s current 2026 ADU Universal Checklist and current permit guidance.
Best first step
Check the real San José address.
Jurisdiction, existing permits, hazards, easements, fire access, utilities, and the usable building area can change the right ADU strategy.
San Jose ADU topic cluster
Go deeper on cost, permits, rules, plans, models and construction.
This hub stays the broad San Jose resource. The guides below answer narrower search and homeowner questions in more depth while linking back to this page and the property-check workflow.
San Jose ADU cost
San Jose ADU Cost in 2026
Open guideSan Jose ADU permits
San Jose ADU Permit Guide for 2026
Open guideSan Jose ADU requirements
San Jose ADU Requirements in 2026
Open guideSan Jose pre-approved ADUs
San Jose Pre-Approved ADU Plans
Open guideSan Jose ADU models
San Jose ADU Models and Floor-Plan Starting Points
Open guideSan Jose garage conversions
San Jose Garage Conversion ADU Guide
Open guideSan Jose ADU projects
San Jose ADU Projects and Construction Examples
Open guideSan Jose ADU financing
San Jose ADU Financing and Budget Planning
Open guide2026 San José ADU rules
City Standards and State Standards are different paths.
San José’s Universal Checklist says you must choose either the City development standards or the State development standards; they cannot be mixed. The table below summarizes the single-family-property rules most useful for early planning. Always reconfirm the current City documents for the actual address.
| Planning item | San José City Standards | State Standards path |
|---|---|---|
| Choose one standards path | Use San José City Standards under Municipal Code 20.80.175. | Use State Standards under Municipal Code 20.80.176. The two paths cannot be mixed. |
| Detached ADU maximum size | Lots under 9,000 sq ft: up to 1,000 sq ft. Lots over 9,000 sq ft: up to 1,200 sq ft. | New attached or detached ADU: 800 sq ft under the State Standards table. |
| Side & rear setbacks | Detached ADU: 0 ft for the first story; 4 ft for the second story. Building and Fire Code still apply. | New attached or detached ADU: 4 ft side and rear setbacks. |
| Height | Detached: 18 ft first story and up to 25 ft for a second story. | New detached: 18 ft, with up to 2 additional feet for a pitched roof where the City rule allows it; attached: 25 ft. |
| Siting & separation | Detached ADU generally behind the main home or behind the zoning district’s 45 ft front setback; minimum 6 ft building separation and rear-yard coverage rules apply. | State path does not use the City siting rule in the same way; front setback may be encroached when no other option enables a minimum 800 sq ft ADU. |
| Parking | No ADU parking requirement in the March 2026 Universal Checklist. | No ADU parking requirement in the March 2026 Universal Checklist. |
Property baseline
The main residence must be legally permitted, and the address must actually be within San José jurisdiction.
Lot-size threshold
Under the City detached-ADU path, the key size threshold is 9,000 sq ft: up to 1,000 sq ft below it and up to 1,200 sq ft above it.
Site constraints
Flood, geohazard, seismic, WUI, easements, former pools, historic status, trees, and fire access can change the review path.
San Jose ADU cost
Use a planning range before asking for a final price.
These live ADU California Inc. ranges use the site’s current calculator assumptions for San Jose, standard finishes, steel framing, and no property-specific utility or difficult-site adders. They are planning estimates—not bids.
600 sq ft · 1 bedroom
Cottage 600
$306,000–$410,000
Includes baseline construction, site-work allowance, design/engineering, San Jose fee adjustment, and contingency assumptions from the current ADU California Inc. calculator.
750 sq ft · 2 bedrooms
Flex 750
$388,500–$521,500
Includes baseline construction, site-work allowance, design/engineering, San Jose fee adjustment, and contingency assumptions from the current ADU California Inc. calculator.
1,000 sq ft · 2 bedrooms
Residence 1000
$529,000–$710,000
Includes baseline construction, site-work allowance, design/engineering, San Jose fee adjustment, and contingency assumptions from the current ADU California Inc. calculator.
What can move the San Jose price: utility service upgrades, sewer/water work, fire requirements, tight access, slope, demolition, geotechnical work, foundation conditions, design changes, premium finishes, solar/electrification scope, and corrections required by the reviewing agencies.
San Jose ADU permit process
A complete package moves faster than a rushed package.
San José uses SJPermits for the application workflow and SJePlans for plan uploads, review comments, and approved documents. The City’s current FAQ says the first building-review round typically takes about 20 business days unless additional review is needed.
01
Complete the ADU Universal Checklist
Confirm San José jurisdiction, a legally permitted main residence, code-enforcement status, flood/geohazard/WUI conditions, easements, and other site constraints.
02
Choose City or State standards
Select one development-standard path before design. San José explicitly says the City and State standards cannot be mixed.
03
Prepare architecture & engineering
Build the formal plan set around Bulletin 211, energy/CalGreen requirements, fire review, site conditions, and any geotechnical or structural scope that applies.
04
Start the application in SJPermits
Use the City application workflow, identify the correct project type, and assign the ePlan Applicant who will own uploads and comment responses.
05
Upload through SJePlans & complete review
The City prescreens the package, invoices initial fees, routes plan review, and handles corrections through SJePlans. The City FAQ says a first building-review round typically takes about 20 business days unless additional review is required.
06
Permit, construct & inspect
After approval and required fees, the permit is issued. Construction then proceeds through required inspections, with the ADU inspection checklist and final diversion sign-off before final inspection.
Utilities & fire review
Solve utility and fire-flow questions early.
San José repeatedly warns applicants not to leave the water-flow letter until the end. Utility service, access, hydrant location, and fire-flow data can affect intake and design.
Hydrant & fire-flow letter
The City requires a letter from the water provider showing flow data at the hydrant nearest the property. City fire guidance uses a 1,000 gpm at 20 psi benchmark; other results can trigger Fire review and additional measures.
Electric service & meters
The City says PG&E may require a separate utility meter for an ADU and directs applicants to PG&E for the current project-specific requirement. JADUs are treated differently.
Separate ADU address
San José requires ADUs and JADUs to receive a separate address as part of the permit process; Form 302 is part of the submittal package.
Hazards & clearances
Flood, geohazard, liquefaction/landslide, WUI, historic, easement, and prior-pool conditions can add design requirements, clearances, reports, or review steps.
San Jose pre-approved ADU plans
Preapproved plans can accelerate review—but the site still has to qualify.
San José’s program uses standard construction plans already reviewed by City staff. The homeowner still needs site-specific documents for placement, setbacks, utilities, fire, zoning, and other property conditions.
- The lot must be residential and have an existing single-family home or duplex for the City’s current preapproved path.
- The City says the site must not be in a geohazard, landslide, flood, or Wildland-Urban Interface area for the expedited preapproved path.
- Plan modifications can move the project out of the expedited preapproved process and into standard ADU review.
- If site-specific plans and required documents are complete and accurate, the City says same-day permit issuance may be available at the scheduled plan-review meeting; deferred structural work, clearances, or variances can take longer.
San Jose ADU timeline
Separate City review time from the full project timeline.
Design & engineering
1–2 months
ADU California Inc. planning model
First City review
About 20 business days
City FAQ typical first round; additional reviews can extend it
Construction
7–10 months
ADU California Inc. standard steel-frame planning model
Preapproved option
Potential same-day issuance
Only at the scheduled review meeting when the site-specific package is complete and eligible
San Jose neighborhoods
Local surroundings. A plan for your property.
Planning an ADU in Willow Glen, a backyard cottage in Rose Garden or a garage conversion in Cambrian? Start with how you want to use the space: multigenerational living, a separate home for relatives or a rental ADU. Then compare access, privacy, outdoor space and the existing home.
We also help homeowners explore ADU design and construction in Almaden Valley, Evergreen, Berryessa, Blossom Valley, Santa Teresa, North San Jose and Downtown San Jose. Each address needs its own review; a neighborhood name does not establish buildability.
Confirm City of San José jurisdiction before using City requirements. A San Jose mailing address can fall outside the incorporated city.
San Jose ADU financing + next step
Know the property, planning range, and permit path before choosing financing.
Financing should follow a realistic project scope. Use the property check and cost calculator first, then compare financing structures against the range you can actually support.
Official San José resources
Go directly to the City when a rule or permit step needs confirmation.
San José permit fees
Use San José’s ADU fee estimate for your project scope.
The City’s Building Permit Fees page provides an ADU fee estimator, currently labeled beta. Use the current City tool or request an agency estimate for the proposed work before setting the permit allowance.
- City permit estimate
- San José Building Permit Fees / ADU estimator
- Amount for this property
- Requires the project’s scope and current agency calculation
- Budget follow-up
- Ask which school, utility and other agency charges are included, and which require separate estimates.
San José planning questions
Bulletin 210, SJePlans and the City’s separate approval paths.
What should I prepare before speaking with a San José planner?
Start with the City’s Universal Checklist and Bulletin 210, then gather the property address, existing-condition information, proposed scope, drawings or site plan, and focused questions. The planner discussion can help identify the applicable path; it does not establish eligibility or replace required professional and agency review.
Can I combine San José city and state ADU standards?
No. The City materials distinguish the city standard in MC 20.80.175 from the state standard in MC 20.80.176. Confirm the applicable path through the City before using its checklist or preparing an application, and do not mix requirements from the two standards.
How do SJPermits and SJePlans fit into the process?
Use SJPermits to check the property’s jurisdiction and begin the City’s application path. The City’s process materials identify SJePlans for electronic plan submission and review responses. Follow the current agency instructions for the address and keep the applicant and correction-response responsibilities clear.
What should I know about the Master Plan or preapproved-ADU path?
The City describes Master Plan and preapproved-ADU options as an available planning path with its own submittal and site requirements. Review the current City materials and confirm what applies to the property. These are City-described resources, not a promise of same-day review, approval, schedule, or suitability from ADU California Inc.
What does AB 1033 mean for a San José ADU condominium or Parcel Map?
San José’s AB 1033 page describes its opt-in condominium-conversion framework and Parcel Map process. Treat that page as informational only: a Parcel Map, condominium conversion, and any required approvals need property-specific confirmation from the City and qualified professionals and are not an eligibility guarantee.
What utility or water-flow questions should I raise early?
Ask the City and the responsible water provider which utility materials apply to the address, including any water-flow letter or hydrant information identified in the process materials. Confirm connection, capacity, and other utility requirements before relying on a concept or budget; this guide does not determine utility feasibility.
A useful first review
Separate what is available from what still needs verification.
01
Confirm the property
Start with a complete address and review the available parcel, building, and map context.
02
Identify the unknowns
Keep missing setbacks, easements, utilities, access, hazards, and local requirements visible.
03
Choose the next review
Use the preliminary result to prepare a focused conversation with the required professionals and agencies.
Explore project types
Compare the scope before choosing a solution.
These pages explain the questions each project type introduces. They do not assert that a particular scope is permitted or suitable for your address.
Compare planning footprints
See common ADU sizes before choosing a design.
These model pages are planning references only. They are not a statement that a particular size is allowed or buildable at a San Jose address.
California directory
Explore more city guides.
The next useful action
Put your address at the center of the conversation.
The online review is preliminary and is not a permit decision, survey, engineering opinion, construction document, final price, or guaranteed schedule.