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 opens the door to a versatile new living space on your existing property — whether you want to create a private workspace. Brother & Brother Builders has supported hundreds of local homeowners bring these projects to life with skill and integrity.
The demand for ADU construction has grown rapidly in recent years, and it's not hard to see why. California state law now makes it easier for homeowners to construct these secondary units, and local municipalities like San Jose have encouraged the trend as a way to increase density responsibly. If you're planning 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 draw on extensive hands-on experience to every ADU construction project. Our team understands the local permitting process, the engineering considerations, and the design choices that make an ADU functional. If you've been thinking about what ADU construction could mean 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 complete living space — including a kitchen, bathroom, sleeping area, and its own entryway — that is located on the same parcel as a primary residence. ADU construction can take several forms, including detached backyard units, attached additions, garage conversions, and even below-grade dwelling units.
Mechanically, everything kicks off with a thorough property evaluation, where our builders evaluate lot dimensions, existing structures, soil conditions, and local code requirements. From there, blueprints are prepared and submitted to the local building department. Once the paperwork is cleared, ADU construction transitions to 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.
What sets quality ADU construction apart is the level of craftsmanship 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 approaches every build with the same technical discipline we bring to full custom home projects.
Key Advantages ADU Construction
- Boosted Home Equity — ADU construction delivers real market value to your property, often increasing appraised value substantially when it's time to sell.
- Revenue Generation — A completed ADU may be listed as a long-term rental or short-term vacation unit, creating ongoing passive income for the homeowner.
- Multi-Generational Living — ADU construction provides adult children a comfortable home of their own without losing proximity to the family.
- Customization Options — From two-bedroom configurations, ADU construction may be customized to your household's priorities.
- Streamlined Approval Process — Recent state legislation has cut down 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 aligns with sustainability goals.
- Independent Living Areas — Unlike a bedroom addition, ADU construction produces a fully self-contained unit where occupants have full privacy.
- Long-Term Investment Security — A well-built ADU continues to produce returns for many years and generates both usable housing and equity growth.
The ADU Construction Process Step by Step
- Property Walkthrough and Feasibility Check — Our builders assess your property to analyze zoning rules, slope conditions, and available square footage. This step tells you exactly what's possible before any resources go toward planning.
- Blueprint Development and Layout Design — Experienced draftspeople create detailed floor plans tailored to your needs. Every square foot is planned to maximize function and livability.
- Filing for Building Permits — ADU construction in San Jose demands documentation to the city's building department for review and approval. Our team handles all submissions on your behalf, addressing any city comments promptly.
- Site Preparation and Foundation Work — Once permits are approved, physical construction begins. This covers land preparation, laying the structural base, and running initial plumbing and electrical conduits.
- Structural Framing and Weatherproofing — Walls and roof systems go up followed by insulation, sheathing, and exterior cladding. This phase, the ADU transforms from a concept to a building.
- Mechanical, Electrical, and Plumbing Installation — Licensed subcontractors install the heating, cooling, drainage, and power infrastructure that make the ADU operationally complete. Inspections are completed at designated stages throughout ADU construction.
- Finishes, Fixtures, and Final Walkthrough — Trim, appliances, tile, and lighting are placed and inspected to the agreed design. A closing municipal review grants legal occupancy status and your new space is cleared for use.
Who Is a Good Candidate for ADU Construction?
Homeowners who benefit most from ADU construction often belong to a few recognizable groups. If you have a residential property 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 needs a dedicated professional workspace and wants a separate office or studio space that doesn't interfere with your family's daily life. Real estate-minded homeowners who already own residential properties are also well suited 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. Sites with underground infrastructure conflicts may need a modified approach. Our team can assess each property case by case to provide realistic options.
ADU Construction Common Questions Answered
How long does ADU construction typically take from start to finish?
The total process for ADU construction usually runs between six to fourteen months, based on the project scope and how quickly approvals come through. City review on its own can take two to four months in San Jose, so planning ahead matters. Smaller detached units may complete more quickly, while larger new construction ADUs fall toward the upper end of the timeline.
What does ADU construction usually run in terms of budget?
Budget requirements differ based on the type and size of the ADU. Locally, ADU construction commonly costs $150,000 to $400,000 or more for a fully custom construction. Interior conversion projects tend to cost less, sometimes between $75,000 and $140,000. A detailed estimate can only be developed after a full site assessment.
Is ADU construction difficult to live through while it's underway?
How much the build affects daily life depends on whether you're converting existing space or building new. New construction in the rear yard are usually easier to live alongside, since the construction zone is separate. Interior conversions may involve some shared wall work during specific stages like framing or MEP rough-in. Our team communicates clearly about upcoming work and timelines.
Do I need to move out during ADU construction?
Generally speaking, you are not required to vacate your primary residence during ADU construction. Most job sites are designed so that you stay in your primary unit throughout the build. Certain situations could require a brief departure if major utility upgrades affect the main house in ways that temporarily impact livability. Our construction supervisors will flag these situations during the pre-construction consultation.
How long will an ADU built through professional ADU construction hold up?
An ADU constructed with quality materials can be expected to last as long as the main residence — often several decades with routine maintenance. Longevity is tied to the quality of materials used, whether the unit is properly cared for, and whether systems like roofing and plumbing are serviced regularly. Brother & Brother Builders specifies high-quality components and follow all code requirements to ensure lasting performance.
ADU Construction for Local Homeowners
Residential areas across San Jose present a wide range 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. The Berryessa area are seeing more homeowners add secondary units as housing demand rises. From neighborhoods near the Guadalupe River Park corridor to those near Branham Lane, our team has project experience in the area.
The City of San Jose's building department applies particular standards for ADU construction that experienced builders know well. Proximity to transit corridors can influence utility connection requirements for a given ADU project. Brother & Brother Builders' experience across these local conditions means fewer surprises from kickoff through certificate of occupancy.
Schedule Your ADU Construction Planning Session Today
Should you be thinking about how to add an ADU to your property, Brother & Brother Builders is the team to call. We bring licensed expertise in ADU construction across a wide range of project types — from simple garage conversions to multi-room backyard residences. Our approach opens with a comprehensive site assessment where we understand your vision and give you a realistic picture of what's achievable.
Reach out to our team to schedule a site visit. No matter where you are in the decision-making process, our team is happy to walk through your options, review completed projects and help you take the next step. Building an ADU is a major check here 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