Expand Your Home with Quality ADU Construction

Property owners throughout San Jose, CA are discovering that adding an accessory dwelling unit is one of the most practical investments they can make. ADU construction opens the door to a versatile new living space on your existing property — whether you want to house a family member. Brother & Brother Builders has guided hundreds of local homeowners see these visions to life with craftsmanship and transparency.

The interest in ADU construction has surged in recent years, and it's easy to understand why. California state law has streamlined permitting for homeowners to add these secondary units, and local municipalities like San Jose have embraced 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 provides increased 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 requirements, and the design choices that make an ADU beautiful. Should you want to learn about what ADU construction could mean for your property, this guide will walk you through everything you need to know.

What Is the ADU Construction Process?

ADU construction describes the process of designing, permitting, and building an accessory dwelling unit on a residential property. An accessory dwelling unit is a self-contained living space — including a kitchen, bathroom, sleeping area, and its own entrance — 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 below-grade dwelling units.

Mechanically, the work starts with a comprehensive review of your lot, where our builders evaluate setbacks, zoning, utility access, and structural feasibility. From there, blueprints are prepared and submitted to the local building department. Once approvals are in place, ADU construction moves into the physical build phase — which includes foundation work, framing, HVAC, drywall, flooring, and exterior finishes. The result is a completely finished living unit adjacent to or detached from your main home.

What sets quality ADU construction apart is the level of craftsmanship at every stage. Components should be specified to complement the existing structure. Systems like HVAC and drainage must be designed to handle full-time occupancy. Brother & Brother Builders handles every ADU construction job with the same technical discipline we use on major 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 can be rented as a long-term rental or short-term vacation unit, creating ongoing passive income for the homeowner.
• Multi-Generational Living — ADU construction offers family members a comfortable home of their own without leaving the property.
• Customization Options — From two-bedroom configurations, ADU construction may be customized to your specific needs.
• Simplified Regulatory Path — Recent state legislation has cut down the barriers and delays associated with ADU construction, making the process that is faster and more affordable than ever before.
• Sustainable Land Use — Building an ADU maximizes the land you already own instead of consuming open land, which contributes to sustainability goals.
• Privacy for All Residents — Unlike a bedroom addition, ADU construction creates a truly separate unit where tenants live autonomously.
• Durable Return on Investment — A well-built ADU remains an asset for many years and generates both functional space and financial upside.

The ADU Construction Journey Step by Step

1. Site Evaluation and Zoning Analysis — Our team visits your property to determine what type of ADU is allowed and where it can be placed. This step tells you exactly what's possible before any time is invested in drawings.
2. Architectural Drafting and Space Planning — Experienced draftspeople create comprehensive blueprints reflecting your priorities. Every square foot is planned to create practical, comfortable living.
3. Permit Submission and Municipal Review — ADU construction in San Jose demands documentation to the city's building department for review and approval. We manage this entire process on your behalf, responding to review feedback promptly.
4. Excavation and Foundation Installation — Once permits are approved, physical construction begins. This involves leveling and prepping the ground, laying the structural base, and setting up utilities.
5. Framing, Roofing, and Exterior Work — The structural frame is erected followed by insulation, sheathing, and exterior cladding. This phase, the ADU transforms from a concept to a building.
6. Interior Systems and Infrastructure — Certified technicians install the heating, cooling, drainage, and power infrastructure that make the ADU ready for occupancy. All work is inspected at designated stages throughout ADU construction.
7. Interior Completion and City Sign-Off — Flooring, cabinetry, fixtures, paint are installed and finished to your specifications. A last official inspection issues the certificate of occupancy and your new space is cleared for use.

Who Is a Right Fit for ADU Construction?

People who see the greatest return from ADU construction generally fit within a few recognizable groups. If you are a homeowner with enough lot space to meet setback requirements, you're already a strong candidate. Homeowners wanting to add a revenue stream click here through rental are among the most financially driven ADU construction clients, along with families accommodating adult children who need housing.

Another strong candidate is someone who works from home and wants a separate office or studio space that is distinct from your family's daily life. Landlords and real estate investors who want to maximize their land are also prime candidates 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 require additional review. Our team can assess each property on its own merits to provide realistic options.

ADU Construction FAQ

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

The complete duration for ADU construction commonly spans six to fourteen months, based on the project scope and city review schedules. The approval phase alone can take several months in San Jose, so starting early is important. Smaller detached units can move faster, while multi-room detached cottages require more time.

What does ADU construction cost in San Jose?

Budget requirements differ based on project complexity and finishes selected. For most projects in this region, ADU construction commonly costs $150,000 to $400,000 or more for a fully custom construction. Garage conversions tend to cost less, sometimes between $75,000 and $140,000. A detailed estimate can only be produced following a thorough property review.

Is ADU construction intrusive while it's underway?

The level of disruption depends on whether you're converting existing space or building new. Detached backyard builds are generally the least intrusive, since the construction zone is separate. Projects that connect to the main structure may involve some shared wall work during key milestones. We provide advance notice about what to expect at each stage.

Do I need to leave my home during ADU construction?

In most cases, you won't have to vacate your house during ADU construction. The vast majority of projects are structured to allow you continue living in the home throughout the construction timeline. Certain situations could require a brief departure if major utility upgrades affect the main house in ways that briefly affect habitability. The team at Brother & Brother Builders will discuss these scenarios during the kickoff meeting.

How long will an ADU built through professional ADU construction last?

An ADU constructed with quality materials can be expected to last as long as the main residence — typically 50 years or more. Longevity is tied to the standard of construction, how well routine maintenance is performed, 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 ensure lasting performance.

ADU Construction for San Jose Homeowners

The communities throughout San Jose provide a variety of property types that are ideally positioned for ADU construction. Property owners near the Almaden Valley area frequently see their parcels accommodate detached backyard units nicely. The Berryessa area are increasingly popular for ADU construction 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 applies particular standards for ADU construction that require a builder familiar with local expectations. Location near major arterials like Story Road or Tully Road can impact the design approach for a given ADU project. Our familiarity with the San Jose permitting environment means more accurate timelines and budgets from the first meeting to the final inspection.

Book Your ADU Construction Assessment 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 builders provide proven skills in ADU construction including all types of project types — from modest studio builds to fully independent secondary homes. The process begins with a detailed, no-pressure consultation where we learn what you're trying to accomplish and share clear expectations of what's achievable.

Get in touch with our office to set up your consultation. Even if you're just exploring the idea, we enjoy 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