Brother & Brother Builders

Expand Your Home 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 generate rental income. Brother & Brother Builders has supported hundreds of local homeowners turn these plans to life with precision and care.

The popularity of ADU construction has grown rapidly in recent years, and it's no mystery. California state law has streamlined permitting for homeowners to build 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 gives you more control over how your property works.

At Brother & Brother Builders, we draw on extensive hands-on experience to every ADU construction build. Our team is familiar with city and county requirements, the engineering details, and the aesthetic decisions that make an ADU beautiful. Should you want to learn about what ADU construction could do for your property, this guide will walk you through everything you need to know.

What Is an ADU Build?

ADU construction describes the process of designing, permitting, and building 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 entryway — that exists on the same lot 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 detailed site assessment, where our builders evaluate property boundaries, available square footage, and infrastructure capacity. From there, design plans are prepared and submitted to the relevant municipal authority. Once permits are secured, ADU construction enters the physical build phase — which includes foundation work, framing, mechanical systems, weatherproofing, and interior finishing. The result is a fully functional living unit connected to or independent of your main home.

The difference between a good and a great ADU build is the attention to detail at every stage. Materials must be selected to match the primary home's aesthetic. Systems like plumbing and electrical must be sized for independent daily use. Brother & Brother Builders treats each project with the same high standards we apply to large-scale custom home projects.

Key Reasons to Choose ADU Construction

• Higher Resale Potential — ADU construction contributes significant market value to your property, often generating strong equity gains when it's time to sell.
• Rental Income Potential — A completed ADU may be listed as a long-term rental or short-term vacation unit, providing a consistent income stream for the homeowner.
• Multi-Generational Living — ADU construction provides adult children a private, independent living space without losing proximity to the family.
• Customization Options — From open-plan one-bedrooms, ADU construction is adaptable 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 cost-efficient than ever before.
• Sustainable Land Use — Building an ADU uses your existing lot instead of expanding urban sprawl, which contributes to sustainability goals.
• Independent Living Areas — Unlike a bedroom addition, ADU construction creates a truly separate unit where residents have their own space.
• Lasting Financial Benefit — A well-built ADU continues to produce returns for many years and generates both functional space and financial upside.

The ADU Construction Procedure Step by Step

1. Site Evaluation and Zoning Analysis — Our builders assess your property to evaluate setbacks, lot coverage limits, and utility connections. This stage clarifies exactly what ADU types will work before any money is spent on design.
2. Architectural Drafting and Space Planning — Our design team create comprehensive blueprints tailored to your needs. Layouts are carefully considered to optimize daily use.
3. Permitting and City Approval — ADU construction in San Jose involves filing drawings to the city's building department for inspection and clearance. Our team handles all submissions on your behalf, responding to review feedback promptly.
4. Excavation and Foundation Installation — Once permits are issued, physical construction begins. This covers land preparation, completing foundation work, and setting up utilities.
5. Framing, Roofing, and Exterior Work — Walls and roof systems go up followed by roofing, siding, windows, and exterior doors. This phase, the ADU becomes recognizable as a structure.
6. Interior Systems and Infrastructure — Licensed subcontractors install the water supply, drain lines, and electrical panel that make the ADU ready for occupancy. All work is inspected at designated stages throughout ADU construction.
7. Finishes, Fixtures, and Final Walkthrough — Trim, appliances, tile, and lighting are fitted and completed to your specifications. A last official inspection grants legal occupancy status and the unit is officially approved for use.

Who Is a Strong Candidate for ADU Construction?

People who see the greatest return from ADU construction often belong to a few recognizable groups. If you own a single-family home with a backyard, garage, or basement that could be converted, you're already a strong candidate. Homeowners looking to generate income through rental are among the most financially driven ADU construction clients, along with families accommodating adult children who need housing.

ADU construction also suits someone who works from home and wants a detached creative or business space that is distinct from your family's daily life. Real estate-minded homeowners who already own residential properties are also prime candidates for ADU construction, since the long-term value is proven.

Homeowners who may want to pause and evaluate include sites with unusual utility access challenges. Parcels in historic districts or HOA-restricted communities may need a modified approach. Brother & Brother Builders reviews each property individually and honestly to advise you on what's feasible.

ADU Construction FAQ

How long does ADU construction usually take from start to finish?

The complete duration for ADU construction commonly spans six to fourteen months, based on the project scope and how quickly approvals come through. The approval phase alone can take a significant portion of the overall timeline in San Jose, so planning ahead matters. Simpler garage conversions may complete more quickly, while larger new construction ADUs fall toward the upper end of the timeline.

What does ADU construction cost in San Jose?

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 are generally priced lower, sometimes in the $80,000 to $150,000 range. A precise cost projection can only be given after completing 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 typically less disruptive, since work happens away from the main house. Garage conversions or attached additions may involve some shared wall work during specific stages like framing or MEP rough-in. Our team communicates clearly about what to expect at each stage.

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 process. Exceptions may arise if major utility upgrades affect the main house in ways that briefly affect habitability. Our construction supervisors 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 should last as long as your primary home — indefinitely with proper upkeep. 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. Our builds use residential-grade products rated for longevity and build to current California residential standards to protect your investment for the long haul.

ADU Construction for Local Homeowners

San Jose's neighborhoods offer a diverse mix of property types that are perfectly suited for ADU construction. Property owners near the Almaden Valley area have found their lots are well configured for ADU builds. Neighborhoods near Blossom Hill Road are seeing more homeowners add secondary units as housing demand rises. If you're located closer to Evergreen, our team has likely worked nearby.

Local regulatory bodies in this area has developed specific protocols for ADU construction that require a builder familiar with local expectations. 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 fewer surprises from the first meeting to the final inspection.

Schedule Your ADU Construction Planning Session Today

Should you be thinking about how to add an ADU to your property, Brother & Brother Builders is here to help. We bring proven skills in ADU construction across a wide range of project types — from small attached additions to multi-room backyard residences. Every project starts with a thorough and honest property review where we listen to your goals and share clear expectations of what the project will involve.

Reach out to our team to schedule a site visit. No matter where you are in the decision-making process, we're glad to discuss timelines, costs, and design possibilities and help you take the next step. 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 read more CA 95117 | (888) 412-2632