Unlock New Space with Professional ADU Construction
Property owners throughout San Jose, CA are discovering 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 integrity.
The interest in ADU construction has grown rapidly in recent years, and it's not hard to see why. California state law has streamlined permitting for homeowners to add these secondary units, and local municipalities like San Jose have supported the trend as a way to increase density responsibly. Whether you're building a detached backyard cottage, a garage conversion, or an attached addition, ADU construction provides increased control over how your property functions.
At Brother & Brother Builders, we bring years of hands-on experience to every ADU construction build. Our team understands the local permitting process, the engineering details, and the planning steps that make an ADU functional. Should you want to learn about what ADU construction could do for your property, this guide covers everything you need to know.
What Is an ADU Build?
ADU construction refers to the process of engineering, filing for, and completing an accessory dwelling unit on a residential property. An accessory dwelling unit is a self-contained living space — equipped with a kitchen, bathroom, sleeping area, and its own entrance — that exists on the same lot as a primary residence. ADU construction can take several forms, including detached backyard units, attached additions, garage conversions, and even basement or interior conversions.
Mechanically, the work starts with a thorough property evaluation, 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 encompasses site preparation, framing, HVAC, drywall, flooring, and exterior finishes. The result is a move-in-ready living unit attached to or separate from your main home.
What separates excellent ADU construction from an average project is the level of craftsmanship at every stage. Products need to be chosen to align with the neighborhood's character. Systems like plumbing and electrical must be sized for independent daily use. Brother & Brother Builders treats each project with the same high standards we bring to full custom home projects.
Key Advantages ADU Construction
- Increased Property Value — ADU construction adds measurable market value to your property, often generating strong equity gains when it's time to sell.
- Rental Income Potential — A completed ADU can be rented as a long-term rental or short-term vacation unit, providing a consistent income stream for the homeowner.
- Housing for Extended Family — ADU construction gives aging parents a comfortable home of their own without leaving the property.
- Design Flexibility — From modern studio layouts, ADU construction may be customized to your specific needs.
- Streamlined Approval Process — Recent state legislation has minimized the red tape associated with ADU construction, resulting in a timeline that is faster and more cost-efficient than ever before.
- Responsible Property Development — Building an ADU uses your existing lot instead of consuming open land, which supports broader sustainability goals.
- Privacy for All Residents — Unlike a bedroom addition, ADU construction delivers a genuinely independent unit where occupants have full privacy.
- Long-Term Investment Security — A well-built ADU continues to produce returns for the long haul by offering both livable square footage and monetary benefit.
The ADU Construction Journey Step by Step
- Property Walkthrough and Feasibility Check — Our team visits your property to evaluate setbacks, lot coverage limits, and utility connections. This phase answers exactly what ADU types will work before any time is invested in drawings.
- Custom Design and Architectural Planning — Our design team create precise architectural drawings based on your goals. Space is thoughtfully allocated to maximize function and livability.
- Filing for Building Permits — ADU construction in San Jose demands documentation to the city's building department for sign-off and verification. We manage this entire process on your behalf, responding to review feedback promptly.
- Excavation and Foundation Installation — Once permits are granted, the build starts. This involves leveling and prepping the ground, pouring the concrete foundation, and running initial plumbing and electrical conduits.
- Shell Construction and Exterior Finishing — The structural frame is erected followed by insulation, sheathing, and exterior cladding. At this stage, the ADU transforms from a concept to a building.
- Interior Systems and Infrastructure — Skilled tradespeople install the water supply, drain lines, and electrical panel that make the ADU fully functional. Every system is reviewed at each code checkpoint throughout ADU construction.
- Finishes, Fixtures, and Final Walkthrough — Countertops, hardware, finishes, and fixtures are installed and finished to the approved plan. 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 common profiles. If you are a homeowner with enough lot space to meet setback requirements, you're already a strong candidate. Homeowners hoping to offset mortgage costs through rental are among the most motivated ADU construction clients, along with families supporting elderly parents.
ADU construction also suits someone who runs a small business and wants a detached creative or business space that remains away from your family's daily life. Landlords and real estate investors who already own residential properties are also a natural fit for ADU construction, since the return on investment is well-documented.
Those who should discuss alternatives first include lots that are below minimum size thresholds. Sites with underground infrastructure conflicts may face additional constraints. Our experts will evaluate each property case by case to provide realistic options.
ADU Construction Common Questions Answered
How long does ADU construction usually take from start to finish?
The complete duration for ADU construction typically ranges from six to fourteen months, depending on design complexity and local permitting timelines. The approval phase alone can take a significant portion of the overall timeline in San Jose, so planning ahead matters. Simpler garage conversions can move faster, while larger new construction ADUs fall toward the upper end of the timeline.
What does ADU construction typically cost?
Costs vary widely based on the type and size of the ADU. Locally, ADU construction typically ranges from $150,000 to $400,000 or more for a detached adu construction San Jose new build. Interior conversion projects are generally priced lower, sometimes starting around $80,000 depending on scope. A detailed estimate can only be given after completing a full site assessment.
Is ADU construction disruptive while it's underway?
How much the build affects daily life depends on the project's location on your property. Standalone ADU projects are typically less disruptive, since the construction zone is separate. Garage conversions or attached additions may require temporary access during specific stages like framing or MEP rough-in. Our team communicates clearly about any phases that may affect your routine.
Do I need to vacate the property during ADU construction?
Generally speaking, you are not required to vacate your primary residence during ADU construction. Most job sites are structured to allow you continue living in the home throughout the build. Certain situations could require a brief departure if interior conversion work touches shared systems in ways that briefly affect habitability. Our project managers will walk you through any potential disruptions during the planning phase.
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 quality of materials used, how consistently minor repairs are addressed, and whether systems like roofing and plumbing are serviced regularly. Brother & Brother Builders specifies commercial-grade materials and comply with all local building codes to deliver a structure that stands the test of time.
ADU Construction for Local Homeowners
San Jose's neighborhoods offer a diverse mix of property types that are ideally positioned for ADU construction. Residents in the Rose Garden district have found their lots accommodate detached backyard units nicely. Communities around the Capitol Expressway corridor are seeing more homeowners add secondary units as families expand. From neighborhoods near the Guadalupe River Park corridor to those near Branham Lane, our team has likely worked nearby.
San Jose's permitting office follows defined procedures for ADU construction that our team navigates routinely. Location near major arterials like Story Road or Tully Road can influence utility connection requirements for a given ADU project. Our familiarity with this region's building landscape means more accurate timelines and budgets from kickoff through certificate of occupancy.
Book Your ADU Construction Consultation Today
If you're ready to explore what an ADU could look like on your lot, Brother & Brother Builders is ready to guide you. Our experts offer years of hands-on experience in ADU construction across a wide range of project types — from modest studio builds to large custom detached cottages. The process begins with a thorough and honest property review where we learn what you're trying to accomplish and give you a realistic picture of what the project will involve.
Get in touch with our office to set up your consultation. Even if you're just exploring the idea, we're glad to answer questions, share examples of our work and give you the clarity you need to move forward. This type of project is a meaningful commitment — 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