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ADU Construction in San Jose, CA

Q: What size ADU can I build in San Jose?

You can build a detached ADU up to 1,200 sq. ft. in most San Jose neighborhoods, and an attached ADU up to 50% of your main home’s living area. Zoning laws and lot size may affect the final allowable size. We’ll handle all zoning reviews to ensure your project meets city requirements.

Q: Are there any special ADU incentives or programs in San Jose?

Yes. San Jose offers pre-approved ADU designs and a streamlined permitting program to reduce planning and construction time. Some homeowners may also qualify for fee reductions or state financing assistance. We’ll guide you through all available options and help you apply for eligible programs.

Q: Can I build both a Junior ADU (JADU) and a standard ADU on my property?

Yes, San Jose allows property owners to build both a JADU and a full ADU on the same lot. This is a great way to maximize your rental income or living space, especially for multigenerational households. We help with layout planning and compliance with local ordinances.

Brother and Brother Builders is your go-to contractor for ADU construction in San Jose, CA. As a trusted general contractor in San Jose, we specialize in building high-quality accessory dwelling units (ADUs) that add value, space, and versatility to your property.

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Meeting All Your Needs

Expert General Contractors in San Jose, CA

Our team includes licensed general contractors, certified designers, and experienced project managers. We take pride in:

Meeting deadlines while maintaining quality standards.
Following OSHA-compliant safety procedures.
Maintaining constant communication throughout your project.

We don’t just build structures—we build relationships based on trust and results.

“B&B remodeled my guest and master bathrooms after a bad experience with another contractor. We were pleased with the superior standard of workmanship. The good communication with all members of the team. we were assigned Daniel, as our project manager who went above and beyond to assist us when we ran into issues of materials procurement. We were also assigned an assistant project manager and a designer who assisted with all material purchases and questions and helped get them ready before our project started. The project was delayed a bit but still completed within the promised time frame. The price was reasonable, and we are happy with the end results.”

X. Madri

“We worked with Zion and his team for remodeling 3 bathrooms, some improvements in the kitchen and remodel a fireplace wall. BnB handled all the permits and inspections smoothly. Miguel was our foreman and his crew including Angel & Giovani were all really skilled and good at their job! Miguel himself is very hands-on and aims for perfection in his work. Even after the project. Zion has been very responsive for any fixes and tweaks to have a better finish to the work. We would recommend them for your next home improvement project! Special mention for Brenda for going above and beyond her role! The team put in extra hours to get our home ready for move-in and we are very grateful. Thank you BnB Team.”

Sanyukta Kabra

“Brother and Brother Builders can be trusted and relied on. I took my permitted plans for a one-bedroom apartment above existing garage to them and they made it a reality! Daniel, Nick and Zion kept me updated on all aspects of the project including timing, budget, finish materials and delays(yes PGE…). The communication with the brother and brother team is top notch as well as the build quality. You simply cannot find this from every company. If you are lucky enough to work with Brother and Brother, you cannot go wrong.”

Nathan Isla

“I’ve never really had a bad contractor, but I have now experienced a great one. My project was completed on time, and everything went smoothly. Reem was very available and responded timely to my questions. Elinor did a fantastic job of helping me find the right porcelain, tile, cabinetry and fixtures AND she provided an awesome 3D rendition of both my bathroom and kitchen. Excellent communication. Julio and team did an exceptional job, everything they did was done with attention to detail. I’m so glad I found Brother and Brother Building, I couldn’t be any happier. Professional, top notch and definitely competitively priced. You will not regret hiring them for your next project.”

Yvette Bonnet

“My wife recently contacted Brother and Brother Builders to renovate our house, and we have nothing but praise for these builders. Reem and his staff provided committed management and went above and beyond to make sure that everything was completed to our satisfaction throughout the process. Reem kept me updated about every step of the project. The job did take a little longer than anticipated, but the outcome was worthwhile. The team is of the highest caliber, and I am delighted with the result.”

Ethan Mason

ADU Regulations in San Jose, CA

The City of San Jose has adopted ADU-friendly policies, including:

Reduced Lot Size Requirements: Most single-family lots qualify for an ADU, even those under 6,000 sq. ft.
Streamlined Permitting: Review timelines have been shortened to 4-6 weeks for compliant designs.
Pre-Approved Plans: The city offers several pre-approved ADU designs to reduce design costs and speed up approvals.
Increased Size Limits: Detached ADUs can be built up to 1,200 sq. ft., and attached units up to 50% of the main home.

Fun Fact: In 2021, San Jose introduced a program that allows homeowners to build both a standard ADU and a Junior ADU (JADU) on the same property, maximizing housing options.

Celebrate Your Space

Solutions Tailored to Your Home

We understand that every home tells a different story. That’s why we:

Customize every project to fit your space and needs.
Offer flexible design options, material choices, and scheduling.
Ensure alignment with your goals from consultation to completion.

Turn Your Ideas Into Reality

From the initial consultation to the final reveal, we’ll work closely with you to ensure that every aspect of your project reflects your unique style and personality.

Brother & Brother Builders can help you create the home of your dreams.

Recent Projects

Check Out Our Latest Projects

From kitchen remodels to new home construction, we take pride in every detail. Explore our latest projects and see how we’ve transformed homes across the Bay Area with expert craftsmanship and personalized design.

Expert Remodeling Services

Why Choose
Brother and Brother Builders

Local Knowledge You Can Trust: Based in San Jose, we know the ins and outs of local zoning laws and neighborhood character—from Willow Glen to Almaden Valley—so your ADU is fully compliant and seamlessly integrated.
All Under One Roof: We keep everything in-house—from architects to builders—so your project benefits from tight coordination, high standards, and a faster timeline. No delays from juggling subcontractors.
Highly Rated by Homeowners: With dozens of glowing testimonials and a strong referral network, our reputation is built on transparency, respect, and quality.
Straightforward Pricing: We believe in no-surprise quotes. Our detailed estimates walk you through every cost up front, so you can plan with confidence.
Eco-Friendly Solutions: Our green building options reduce your environmental impact with energy-efficient appliances, smart layouts, and sustainable materials.
Award-Winning Craftsmanship: With 20+ years in the Bay Area, we deliver top-tier builds that meet and exceed client expectations.
Permitting Made Easy: We’re fluent in the City of San Jose Building Department process, helping you avoid costly delays and get approved faster.

Our San Jose ADU Services

At Brother and Brother Builders, we handle every phase of the ADU construction process. Our services include:

Site Evaluation and Feasibility Study

We begin by assessing your lot’s suitability for an ADU. This includes zoning compliance, utility access, available square footage, and setbacks. We also help you understand the best ADU type for your property, whether detached, attached, or a conversion.

Custom ADU Design

Our in-house architects create tailored ADU plans that reflect your lifestyle and comply with San Jose’s development guidelines. We balance form and function to create efficient, modern living spaces. Pre-approved designs are also available for faster approvals. Interested in layouts? See our floor plan development services.

Permit Processing

We manage all communication with the City of San Jose to obtain required permits. Our team understands the latest state and local ADU legislation, ensuring that your project navigates smoothly through bureaucracy and avoids costly delays.

Construction and Project Management

Our skilled craftsmen use high-quality materials to construct durable, attractive ADUs. We manage every subcontractor, delivery, and timeline to ensure the project stays on schedule. Weekly updates keep you informed at every step. Need full-service home updates? Explore our design and build offerings.

Interior Finish and Final Inspection

We finish your ADU with quality flooring, cabinetry, lighting, and appliances. Our energy-efficient features help reduce utility costs. Before handoff, we walk through every detail and prepare your ADU for city inspection and final approval. We can also assist with tile work replacement and other interior improvements.

How San Jose's Preapproved ADU Program Works

San Jose runs a Preapproved ADU program. Preapproved ADUs are standard construction plans that City staff have already reviewed for code compliance, and the City describes them as the fastest and lowest-cost permit path. The plans come from vendors, which can be ADU companies, private contractors, or licensed architects and designers. The ADU plans the City currently lists as approved range from 476 to 799 sq. ft., and other plans are still under review and not yet eligible for expedited review.

A preapproved plan does not remove every step. You still submit site-specific documents that show where the ADU sits on your lot, the utility connections, setbacks and other zoning items. If those documents are accurate and complete, the City says permits may be issued the same day as the scheduled plan review meeting. Projects with a deferred site-specific structural submittal, clearances or variances can take longer.

To use a preapproved plan, your property must meet all of these conditions:

The lot is zoned residential and has an existing single-family home or duplex.
The lot is not in a geohazard zone, landslide zone, flood zone or Wildland-Urban Interface (WUI) area. You can check your address on Sjpermits.org.

The City also advises having the vendor or contractor pull the permits, which keeps the liability for the work with the professional. Source: City of San José, Preapproved ADUs

For the full rules, permit steps, fees and rental options, read our guide to building an ADU in San Jose.

ADU Types and State Size, Setback and Height Rules

The City of San José recognizes three kinds of units. An ADU is a small living unit with a kitchen and bathroom on a residentially zoned lot, including single-family, duplex and multifamily properties. A Junior ADU (JADU) is less than 500 sq. ft. and sits within the footprint of a single-family home, and it can be converted from existing space, including an attached garage. A tiny home on wheels (THOW) is a type of ADU allowed only on single-family properties, with a simpler, lower-cost permit process. Source: City of San José, Accessory Dwelling Units

State law also sets a floor under local size, setback and height rules. A city cannot cap an ADU below these limits:

State rule	Minimum a city must allow
Maximum size cap	At least 850 sq. ft. of interior livable space, or 1,000 sq. ft. for an ADU with more than one bedroom
Size and setbacks	An ADU of at least 800 sq. ft. with four-foot side and rear setbacks
Detached ADU height	16 feet, or 18 feet within a half mile walking distance of a major transit stop or high-quality transit corridor
Attached ADU height	25 feet or the local height limit for the main house, whichever is lower

Source: California Government Code 66321. If you are weighing a conversion against new space, see our garage conversion and room additions pages.

ADU Permit Deadlines Under California Law

California law puts deadlines on ADU permit review, and they were tightened by SB 543, effective January 1, 2026. An ADU application must be approved ministerially, without a discretionary hearing. The permitting agency has these deadlines:

Completeness check: within 15 business days of receiving the application, the agency must tell you in writing whether it is complete. If it is incomplete, it must list the missing items and explain how to fix them. If the agency misses this deadline, the application is deemed complete.
Decision: when there is already a single-family or multifamily home on the lot, the agency must approve or deny a complete application within 60 days. If it does not act in time, the application is deemed approved.
Denial comments: a denial must come with a full written list of what is defective and how to fix it, and the applicant can appeal in writing.

Source: California Government Code 66317

For San Jose homeowners, this means the quality of the first submittal matters. A complete set of site plans, utility details and setback information avoids a round of corrections. With a preapproved plan, a complete submittal can lead to same-day permit issuance at the plan review meeting. Our design-build team prepares the drawings and the permit package together.

Areas We Serve

We proudly serve homeowners throughout San Jose, from established neighborhoods like Willow Glen and Naglee Park to the foothill communities of Almaden Valley, Cambrian Park, and Evergreen, as well as Berryessa and Alum Rock. Our reach extends beyond San Jose to Santa Clara, Sunnyvale, Los Gatos, Saratoga, Milpitas, Cupertino, Campbell, Palo Alto, and Los Altos. Based on Stevens Creek Boulevard in San Jose, we’re centrally positioned to serve the entire South Bay with the same response time and craftsmanship on every project.

Brother & Brother Builders
3109 Stevens Creek Blvd, San Jose, CA 95117

Phone: (888) 412-2632
Business Hours: Mon-Fri: 8AM – 5PM

How much does it cost to build an ADU in San Jose, CA?

In San Jose, the average cost of building an ADU ranges from $150,000 to $400,000, depending on the type (garage conversion, attached, or detached), finishes, and site conditions. At Brother and Brother Builders, we provide detailed estimates tailored to your property and budget. We also help you understand cost-saving options like using pre-approved ADU plans.

What size ADU can I build in San Jose?

You can build a detached ADU up to 1,200 sq. ft. in most San Jose neighborhoods, and an attached ADU up to 50% of your main home’s living area. Zoning laws and lot size may affect the final allowable size. We’ll handle all zoning reviews to ensure your project meets city requirements.

Are there any special ADU incentives or programs in San Jose?

Yes. San Jose offers pre-approved ADU designs and a streamlined permitting program to reduce planning and construction time. Some homeowners may also qualify for fee reductions or state financing assistance. We’ll guide you through all available options and help you apply for eligible programs.

Can I build both a Junior ADU (JADU) and a standard ADU on my property?

Yes, San Jose allows property owners to build both a JADU and a full ADU on the same lot. This is a great way to maximize your rental income or living space, especially for multigenerational households. We help with layout planning and compliance with local ordinances.

Do ADUs require separate utility connections in San Jose?

It depends on the type of ADU and existing utility setup. Detached ADUs typically require separate utility hookups, while garage conversions and attached units may share some systems. Our team works closely with local utility providers to ensure efficient and compliant connections.

How long does it take to get an ADU permit in San Jose?

If you use a pre-approved ADU design, permits can be issued in as little as 4 to 6 weeks. Custom designs typically take 8 to 12 weeks, depending on complexity and zoning requirements. Brother and Brother Builders manages the entire permit process for you to minimize delays.

Is the $40,000 California ADU grant still available?

No new funding is open right now. The California Housing Finance Agency says the latest round of its ADU Grant Program was fully allocated on December 28, 2023. CalHFA also warns that anyone who approaches you saying they can help you get an ADU grant is running a financial scam.

Can a tiny home on wheels count as an ADU in San Jose?

Yes. The City of San José treats tiny homes on wheels as a type of ADU. They are allowed only on single-family properties and have different requirements, with a simpler, lower-cost permit process than a standard ADU. The City’s Bulletin 291, the Tiny Home on Wheels Permit Checklist, lists the requirements.

Who should pull the permit for a preapproved ADU in San Jose?

The City of San José highly advises having the plan vendor or your contractor pull the permits, because it keeps the liability for the work with the professional. Before you sign, confirm who will submit the plans and site-specific documents and who will secure the building permit.

Frequently Asked Questions

All Your Remodeling Questions Answered

Have questions about remodeling your home? We’ve got answers. From budgeting and timelines to permits and design choices, our FAQs cover the most common concerns. Learn what to expect, how to prepare, and how we make your remodel smooth, transparent, and stress-free.