Unlock New Space with Expert ADU Construction
Families in San Jose, CA are realizing that adding an accessory dwelling unit is one of the most practical investments they can make. ADU construction opens the door to a powerful new living space on your existing property — whether you want to house a family member. Brother & Brother Builders has guided hundreds of local homeowners bring these projects to life with craftsmanship and care.
The demand for ADU construction has surged in recent years, and it's easy to understand why. California state law has simplified the process for homeowners to construct these secondary units, and local municipalities like San Jose have supported the trend as a way to expand the housing supply. Whether you want to build a detached backyard cottage, a garage conversion, or an attached addition, ADU construction offers greater control over how your property functions.
At Brother & Brother Builders, we apply deep hands-on experience to every ADU construction build. Our team is familiar with city and county requirements, the engineering requirements, and the aesthetic decisions that make an ADU beautiful. If you've been thinking about what ADU construction could do for your property, this guide explains everything you need to know.
What Is ADU Construction?
ADU construction describes the process of planning, approving, and constructing an accessory dwelling unit on a residential property. An accessory dwelling unit is a fully independent living space — including a kitchen, bathroom, sleeping area, and its own entryway — that sits on the same property as a primary residence. ADU construction includes various structural types, including detached backyard units, attached additions, garage conversions, and even basement or interior conversions.
Mechanically, the process begins with a comprehensive review of your lot, where our builders evaluate lot dimensions, existing structures, soil conditions, and local code requirements. From there, design plans are prepared and submitted to the relevant municipal authority. Once permits are secured, ADU construction moves into the physical build phase — which encompasses site preparation, framing, roofing, plumbing, electrical, insulation. The result is a fully functional living unit adjacent to or detached from your main home.
What sets quality ADU construction apart is the depth of planning at every stage. Components should be specified to align with the neighborhood's character. Systems like plumbing and electrical must be built for long-term residential demand. Brother get more info & Brother Builders approaches every build with the same professional rigor we use on major custom home projects.
Key Advantages ADU Construction
- Boosted Home Equity — ADU construction adds measurable market value to your property, often generating strong equity gains when it's time to sell.
- Revenue Generation — A completed ADU can be rented as a long-term rental or short-term vacation unit, creating ongoing passive income for the homeowner.
- Space for Loved Ones — ADU construction provides adult children a comfortable home of their own without moving to another neighborhood.
- Design Flexibility — From modern studio layouts, ADU construction can be tailored to the intended occupant's lifestyle.
- Simplified Regulatory Path — Recent state legislation has reduced the red tape associated with ADU construction, resulting in a timeline that is faster and more affordable than ever before.
- Sustainable Land Use — Building an ADU maximizes the land you already own instead of expanding urban sprawl, which contributes to sustainability goals.
- Separate Entrances and Spaces — Unlike a bedroom addition, ADU construction creates a truly separate unit where tenants live autonomously.
- Lasting Financial Benefit — A well-built ADU remains an asset for decades, providing both functional space and financial upside.
The ADU Construction Process Step by Step
- Initial Property Assessment and Feasibility Review — Our experts review your property to determine what type of ADU is allowed and where it can be placed. This step tells you exactly what's possible before any resources go toward planning.
- Custom Design and Architectural Planning — Licensed architects and designers create detailed floor plans based on your goals. Layouts are carefully considered to create practical, comfortable living.
- Filing for Building Permits — ADU construction in San Jose involves filing drawings to the city's building department for sign-off and verification. We manage this entire process on your behalf, addressing any city comments promptly.
- Excavation and Foundation Installation — Once permits are issued, physical construction begins. This covers land preparation, pouring the concrete foundation, and establishing utility connections.
- Framing, Roofing, and Exterior Work — Framing is completed followed by insulation, sheathing, and exterior cladding. During this step, the ADU transforms from a concept to a building.
- Mechanical, Electrical, and Plumbing Installation — Certified technicians install the plumbing lines, electrical wiring, and HVAC systems that make the ADU fully functional. Inspections are completed at each code checkpoint throughout ADU construction.
- Interior Completion and City Sign-Off — Trim, appliances, tile, and lighting are fitted and completed to the agreed design. A closing municipal review issues the certificate of occupancy and your new space is cleared for use.
Who Is a Good Candidate for ADU Construction?
People who see the greatest return from ADU construction generally fit within a few recognizable groups. If you are a homeowner with available square footage under zoning rules, you're already in a good starting place. Homeowners wanting to add a revenue stream through rental are among the most motivated ADU construction clients, along with families supporting elderly parents.
You may also be someone who runs a small business and wants a separate office or studio space that doesn't interfere with your family's daily life. Landlords and real estate investors who are building a portfolio are also a natural fit for ADU construction, since the return on investment is well-documented.
Situations where ADU construction may not be the best first step include properties with significant setback limitations. Sites with underground infrastructure conflicts may require additional review. Brother & Brother Builders reviews each property case by case to recommend the right path forward.
ADU Construction Frequently Asked Questions
How long does ADU construction usually take from start to finish?
The full timeline for ADU construction typically ranges from six to fourteen months, based on the project scope and local permitting timelines. City review on its own can take several months in San Jose, so starting early is important. Smaller detached units may complete more quickly, while larger new construction ADUs require more time.
What does ADU construction cost in San Jose?
Costs vary widely based on the type and size of the ADU. In the San Jose area, ADU construction typically ranges from $150,000 to $400,000 or more for a standalone backyard unit. Garage conversions tend to cost less, sometimes in the $80,000 to $150,000 range. An accurate budget can only be given after completing a formal feasibility evaluation.
Is ADU construction difficult to live through while it's underway?
How much the build affects daily life depends on where the ADU is being built. Detached backyard builds are generally the least intrusive, since the crew operates at a distance from your living areas. Projects that connect to the main structure may involve some shared wall work during key milestones. Brother & Brother Builders keeps you informed about what to expect at each stage.
Do I need to move out during ADU construction?
In most cases, you won't have to vacate your house during ADU construction. Most builds are designed so that you remain on the property throughout the build. Exceptions may arise if major utility upgrades affect the main house in ways that briefly affect habitability. Our project managers will flag these situations during the pre-construction consultation.
How long will an ADU built through professional ADU construction last?
Any ADU built to code with professional oversight can be expected to last as long as your primary home — typically 50 years or more. Longevity is tied to the standard of construction, how well routine maintenance is performed, and whether systems like roofing and plumbing are serviced regularly. Brother & Brother Builders specifies high-quality components and comply with all local building codes to ensure lasting performance.
ADU Construction for Local Homeowners
The communities throughout San Jose provide a diverse mix of property types that are perfectly suited for ADU construction. Homeowners in the Willow Glen neighborhood often discover their properties work well for both attached and detached projects. The Berryessa area have seen growing ADU activity as multigenerational living becomes more common. If you're located closer to Evergreen, our team has project experience in the area.
Local regulatory bodies in this area applies particular standards for ADU construction that require a builder familiar with local expectations. Proximity to transit corridors can affect how quickly permits are approved for a given ADU project. Brother & Brother Builders' experience across these local conditions means more accurate timelines and budgets from the first meeting to the final inspection.
Schedule Your ADU Construction Consultation Today
If you're ready to explore what an ADU could look like on your lot, Brother & Brother Builders is here to help. Our builders provide proven skills in ADU construction across a wide range of project types — from simple garage conversions to fully independent secondary homes. Every project starts with a comprehensive site assessment where we understand your vision and give you a realistic picture of what ADU construction on your property will look like.
Get in touch with our office to schedule a site visit. No matter where you are in the decision-making process, our team is happy to discuss timelines, costs, and design possibilities and make sure you feel confident before committing. ADU construction is a significant investment — and we want to make sure it's the right one for you.
Brother & Brother Builders | 3109 Stevens Creek Boulevard | San Jose CA 95117 | (888) 412-2632