Unlock New Space with Expert ADU Construction
Homeowners across San Jose, CA are finding that adding an accessory dwelling unit is one of the most rewarding investments they can make. ADU construction creates a powerful new living space on your existing property — whether you want to generate rental income. Brother & Brother Builders has guided hundreds of local homeowners see these visions to life with precision and integrity.
The interest in ADU construction has grown rapidly in recent years, and it's easy to understand why. California state law has simplified the process for homeowners to build 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 works.
At Brother & Brother Builders, we bring years of hands-on experience to every ADU construction project. Our team is familiar with city and county requirements, the engineering considerations, 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 covers everything you need to know.
What Is an ADU Build?
ADU construction involves 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 — equipped with a kitchen, bathroom, sleeping area, and its own entrance — that is located on the same parcel as a primary residence. ADU construction comes in multiple configurations, including detached backyard units, attached additions, garage conversions, and even interior space reconfigurations.
Mechanically, the work starts with a detailed site assessment, where our professionals evaluate lot dimensions, existing structures, soil conditions, and local code requirements. From there, blueprints are prepared and submitted to the local building department. Once permits are secured, ADU construction enters the physical build phase — which includes foundation work, framing, roofing, plumbing, electrical, insulation. The result is a fully functional living unit attached to or separate from your main home.
The difference between a good and a great ADU build is the depth of planning at every stage. Materials must be selected to complement the existing structure. Systems like wiring and water supply must be built for long-term residential demand. Brother & Brother Builders approaches every build with the same technical discipline we use on major custom home projects.
Key Advantages ADU Construction
- Increased Property Value — ADU construction delivers real market value to your property, often returning more than the build cost 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 offers family members a self-contained residence without moving to another neighborhood.
- Personalized Layouts — From open-plan one-bedrooms, ADU construction may be customized to your household's priorities.
- Streamlined Approval Process — Recent state legislation has minimized the red tape associated with ADU construction, resulting in a timeline that is faster and more affordable than ever before.
- Efficient Use of Your Lot — Building an ADU maximizes the land you already own instead of expanding urban sprawl, which aligns with sustainability goals.
- Independent Living Areas — Unlike a bedroom addition, ADU construction produces a fully self-contained unit where residents have their own space.
- Lasting Financial Benefit — A well-built ADU remains an asset for many years and generates both usable housing and equity growth.
The ADU Construction Process Step by Step
- Site Evaluation and Zoning Analysis — Our builders assess your property to determine what type of ADU is allowed and where it can be placed. This phase answers exactly what's possible before any time is invested in drawings.
- Blueprint Development and Layout Design — Experienced draftspeople create detailed floor plans based on your goals. Every square foot is planned to optimize daily use.
- Filing for Building Permits — ADU construction in San Jose involves filing drawings to the city's building department for inspection and clearance. We manage this entire process on your behalf, resolving any revision requests promptly.
- Ground Prep and Structural Base — Once permits are issued, on-site work kicks off. This involves leveling and prepping the ground, pouring the concrete foundation, and setting up utilities.
- Structural Framing and Weatherproofing — Walls and roof systems go up followed by roofing, siding, windows, and exterior doors. At this stage, the ADU takes its visible shape.
- MEP Systems Rough-In — Skilled tradespeople install the water supply, drain lines, and electrical panel that make the ADU operationally complete. Every system is reviewed at required milestones 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 grants legal occupancy status and the unit is officially approved for use.
Who Is a Good Candidate for ADU Construction?
Property owners who are best suited from ADU construction generally fit within a few common profiles. If you own a single-family home with enough lot space to meet setback requirements, you're already well-positioned. Homeowners hoping to offset mortgage costs through rental are among the most motivated ADU construction clients, along with families accommodating adult children who need housing.
Another strong candidate is someone who works from home and wants a private work environment that is distinct from your family's daily life. Property investors and rental owners who are building a portfolio are also a natural fit for ADU construction, since the long-term value is proven.
Homeowners who may want to pause and evaluate include lots that are below minimum size thresholds. Very small lots or properties with easements may need a modified approach. Our experts will evaluate each property case by case to recommend the right path forward.
ADU Construction FAQ
How long does ADU construction usually take from start to finish?
The full timeline for ADU construction usually runs between six to fourteen months, influenced by the type of unit being built and city review schedules. The approval phase alone can take a significant portion of the overall timeline in San Jose, so starting early is important. Straightforward interior conversions often finish in the lower end of the range, while multi-room detached cottages require more time.
What does ADU construction usually run in terms of budget?
Budget requirements differ based on the type and size of the ADU. For most projects in this region, ADU construction generally falls between $150,000 to $400,000 or more for a detached new build. Attached ADU additions are generally priced lower, sometimes starting around $80,000 depending on scope. A precise cost projection can only be produced following a thorough property review.
Is ADU construction disruptive while it's underway?
The level of disruption depends on the project's location on your property. Standalone ADU projects are generally the least intrusive, since work happens away from the main house. Garage conversions or attached additions may create short-term inconveniences during certain phases of construction. Our team communicates clearly about upcoming work and timelines.
Do I need to move out during ADU construction?
For the majority of homeowners, you won't have to vacate your main home during ADU construction. Most job sites are structured to allow you remain on the property throughout the build. Certain situations could require a brief departure if significant structural connections require temporary shutoffs in ways that temporarily impact livability. The team at Brother & Brother Builders will discuss these scenarios during the planning phase.
How long will an ADU built through professional ADU construction hold up?
An ADU constructed with quality materials is designed to last as long as your primary home — often several decades with routine maintenance. How long it lasts comes down to the quality of materials used, how consistently minor repairs are addressed, and whether systems like roofing and plumbing are serviced regularly. We select residential-grade products rated for longevity and follow all code requirements 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. Homeowners in the Willow Glen neighborhood frequently see their parcels accommodate detached backyard units nicely. The Berryessa area are seeing more homeowners add secondary units as multigenerational living becomes more common. Whether your property is near downtown San Jose, our team has likely worked nearby.
The City of San Jose's building department has developed specific protocols for ADU construction that our team navigates routinely. Proximity to transit corridors can affect how quickly permits are approved for a given ADU project. Our familiarity with the San Jose permitting environment means smoother project delivery from design through the final walkthrough.
Schedule Your ADU Construction Consultation Today
Should you be thinking about how to adu construction add an ADU to your property, Brother & Brother Builders is the team to call. Our experts offer proven skills in ADU construction across a wide range of project types — from modest studio builds to multi-room backyard residences. Every project starts with a comprehensive site assessment where we listen to your goals and provide an honest assessment of what ADU construction on your property will look like.
Contact Brother & Brother Builders to begin the conversation. Whether you're in the early stages of planning, our team is happy to walk through your options, review completed projects and make sure you feel confident before committing. Building an ADU is a major decision — and our goal is to ensure it delivers real value.
Brother & Brother Builders | 3109 Stevens Creek Boulevard | San Jose CA 95117 | (888) 412-2632