Expand Your Home with Professional ADU Construction
Families in San Jose, CA are realizing that adding an accessory dwelling unit is one of the smartest investments they can make. ADU construction creates a versatile new living space on your existing property — whether you want to house a family member. Brother & Brother Builders has helped hundreds of local homeowners bring these projects to life with craftsmanship and care.
The interest in ADU construction has increased significantly in recent years, and it's not hard to see why. California state law has simplified the process for homeowners to add these secondary units, and local municipalities like San Jose have embraced the trend as a way to increase density responsibly. Whether you want to build a detached backyard cottage, a garage conversion, or an attached addition, ADU construction gives you more control over how your property works.
At Brother & Brother Builders, we bring years of hands-on experience to every ADU construction project. Our team understands the local permitting process, the engineering requirements, and the planning steps that make an ADU functional. Should you want to learn about what ADU construction could look like on your property, this guide explains everything you need to know.
What Is the ADU Construction Process?
ADU construction refers to the process of designing, permitting, and building an accessory dwelling unit on a residential property. An accessory dwelling unit is a complete living space — including a kitchen, bathroom, sleeping area, and its own entryway — that sits on the same property as a primary residence. ADU construction comes in multiple configurations, including detached backyard units, attached additions, garage conversions, and even interior space reconfigurations.
Mechanically, everything kicks off 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 city for permit approval. Once approvals are in place, ADU construction enters the physical build phase — which includes foundation work, framing, HVAC, drywall, flooring, and exterior finishes. The result is a completely finished living unit attached to or separate from your main home.
What sets quality ADU construction apart is the attention to detail at every stage. Products need to be chosen to complement the existing structure. Systems like wiring and water supply must be built for long-term residential demand. Brother & Brother Builders treats each project with the same professional rigor we use on major custom home projects.
Key Benefits ADU Construction
- Boosted Home Equity — ADU construction delivers real market value to your property, often generating strong equity gains when it's time to sell.
- Monthly Cash Flow — A completed ADU may be listed as a long-term rental or short-term vacation unit, generating steady monthly revenue for the homeowner.
- Housing for Extended Family — ADU construction provides adult children a self-contained residence without moving to another neighborhood.
- Customization Options — From two-bedroom configurations, ADU construction can be tailored to your household's priorities.
- Streamlined Approval Process — Recent state legislation has minimized the barriers and delays associated with ADU construction, resulting in a timeline that is faster and less expensive than ever before.
- Sustainable Land Use — Building an ADU works within your current footprint instead of requiring new development, which supports broader sustainability goals.
- Separate Entrances and Spaces — Unlike a bedroom addition, ADU construction delivers a genuinely independent unit where occupants have full privacy.
- Long-Term Investment Security — A well-built ADU remains an asset for decades, providing both livable square footage and monetary benefit.
The ADU Construction Journey Step by Step
- Property Walkthrough and Feasibility Check — Our experts review your property to determine what type of ADU is allowed and where it can be placed. This phase answers exactly what ADU types will work before any resources go toward planning.
- Custom Design and Architectural Planning — Licensed architects and designers create detailed floor plans tailored to your needs. Space is thoughtfully allocated to maximize function and livability.
- Filing for Building Permits — ADU construction in San Jose involves filing drawings to the city's building department for inspection and clearance. Brother & Brother Builders coordinates the permitting on your behalf, responding to review feedback promptly.
- Site Preparation and Foundation Work — Once permits are granted, physical construction begins. This covers land preparation, completing foundation work, and running initial plumbing and electrical conduits.
- Shell Construction and Exterior Finishing — Framing is completed followed by insulation, sheathing, and exterior cladding. During this step, the ADU becomes recognizable as a structure.
- MEP Systems Rough-In — Licensed subcontractors install the water supply, drain lines, and electrical panel that make the ADU ready for occupancy. All work is inspected at required milestones throughout ADU construction.
- Interior Finishing and Final Inspections — Countertops, hardware, finishes, and fixtures are fitted and completed to the agreed design. A closing municipal review issues the certificate of occupancy and the ADU is ready for use.
Who Is a Good Candidate for ADU Construction?
Homeowners who benefit most from ADU construction generally fit within a few clear categories. If you have a residential property with available square footage under zoning rules, you're already a strong candidate. Homeowners hoping to offset mortgage costs through rental are among the most common ADU construction clients, along with families supporting elderly parents.
Another strong candidate is someone who needs a dedicated professional workspace and wants a private work environment that remains away from your family's daily life. Real estate-minded homeowners who are building a portfolio are also prime candidates for ADU construction, since rental income frequently offsets build costs.
Homeowners who may want to pause and evaluate include properties with significant setback limitations. Sites with underground infrastructure conflicts may need a modified approach. Our experts will evaluate each property on its own merits to provide realistic options.
ADU Construction Frequently Asked Questions
How long does ADU construction typically take from start to finish?
The full timeline for ADU construction usually runs between six to fourteen months, based on the project scope and local permitting timelines. Permitting alone can take a significant portion click here of the overall timeline in San Jose, so starting early is important. Simpler garage conversions can move faster, while larger new construction ADUs take longer to complete.
What does ADU construction usually run in terms of budget?
Costs vary widely based on project complexity and finishes selected. Locally, ADU construction generally falls between $150,000 to $400,000 or more for a detached new build. Garage conversions are generally priced lower, sometimes between $75,000 and $140,000. A detailed estimate can only be developed after a formal feasibility evaluation.
Is ADU construction disruptive while it's underway?
The day-to-day impact depends on the project's location on your property. 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 specific stages like framing or MEP rough-in. Brother & Brother Builders keeps you informed about what to expect at each stage.
Do I need to leave my home during ADU construction?
For the majority of homeowners, you won't have to vacate your primary residence during ADU construction. The vast majority of projects are designed so that you remain on the property throughout the process. There are edge cases if significant structural connections require temporary shutoffs in ways that temporarily impact livability. Our construction supervisors will discuss these scenarios during the kickoff meeting.
How long will an ADU built through professional ADU construction hold up?
A well-built ADU can be expected to last as long as the main residence — often several decades with routine maintenance. How long it lasts comes down to the systems installed, whether the unit is properly cared for, and if mechanical components are maintained on schedule. Our builds use commercial-grade materials 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. Property owners near the Almaden Valley area often discover their properties work well for both attached and detached projects. Communities around the Capitol Expressway corridor have seen growing ADU activity as housing demand rises. If you're located closer to Evergreen, our team knows the permitting landscape well.
The City of San Jose's building department has developed specific protocols 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 this region's building landscape means more accurate timelines and budgets from design through the final walkthrough.
Schedule Your ADU Construction Assessment Today
When you want to explore what an ADU could look like on your lot, Brother & Brother Builders is here to help. Our experts offer licensed expertise in ADU construction across a wide range of project types — from small attached additions to fully independent secondary homes. The process begins with a detailed, no-pressure consultation where we listen to your goals and give you a realistic picture of what ADU construction on your property will look like.
Reach out to our team to set up your consultation. No matter where you are in the decision-making process, we enjoy answer questions, share examples of our work and give you the clarity you need to move forward. Building an ADU is a major decision — and we're committed to helping you get it right.
Brother & Brother Builders | 3109 Stevens Creek Boulevard | San Jose CA 95117 | (888) 412-2632