Brother & Brother Builders

Unlock New Space with Quality ADU Construction

Property owners throughout San Jose, CA are realizing that adding an accessory dwelling unit is one of the most rewarding investments they can make. ADU construction opens the door to a powerful new living space on your existing property — whether you want to generate rental income. Brother & Brother Builders has supported hundreds of local homeowners see these visions to life with precision and care.

The demand for ADU construction has grown rapidly in recent years, and it's easy to understand 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 expand the housing supply. Whether you're building 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 build. Our team is familiar with city and county requirements, the engineering requirements, and the planning steps that make an ADU beautiful. Should you want to learn about what ADU construction could look like on your property, this guide covers everything you need to know.

What Is the ADU Construction Process?

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 complete living space — including a kitchen, bathroom, sleeping area, and its own entryway — that sits on the same property as a primary residence. ADU construction comes in multiple configurations, including detached backyard units, attached additions, garage conversions, and even below-grade dwelling units.

Mechanically, the process begins with a comprehensive review of your lot, where our professionals evaluate property boundaries, available square footage, and infrastructure capacity. From there, blueprints are prepared and submitted to the relevant municipal authority. Once the paperwork is cleared, ADU construction moves into the physical build phase — which covers everything from foundational work, framing, HVAC, drywall, flooring, and exterior finishes. The result is a completely finished living unit attached to or separate from your main home.

What sets quality ADU construction apart is the depth of planning at every stage. Materials must be selected to complement the existing structure. Systems like plumbing and electrical must be sized for independent daily use. Brother & Brother Builders handles every ADU construction job with the same technical discipline we bring to full custom home projects.

Key Advantages ADU Construction

• Higher Resale Potential — ADU construction contributes significant market value to your property, often returning more than the build cost when it's time to sell.
• Revenue Generation — A completed ADU can be rented as a long-term rental or short-term vacation unit, creating ongoing passive income for the homeowner.
• Housing for Extended Family — ADU construction provides adult children a private, independent living space without moving to another neighborhood.
• Personalized Layouts — From two-bedroom configurations, ADU construction is adaptable to your specific needs.
• Streamlined Approval Process — Recent state legislation has minimized the barriers and delays associated with ADU construction, resulting in a timeline that is faster and more affordable 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 delivers a genuinely independent unit where residents have their own space.
• Lasting Financial Benefit — A well-built ADU continues to produce returns for decades, providing both livable square footage and monetary benefit.

The ADU Construction Process Step by Step

1. 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 step tells you exactly what can be built before any time is invested in drawings.
2. Blueprint Development and Layout Design — Experienced draftspeople create detailed floor plans reflecting your priorities. Every square foot is planned to create practical, comfortable living.
3. Permit Submission and Municipal Review — ADU construction in San Jose involves filing drawings to the city's building department for sign-off and verification. Our team handles all submissions on your behalf, responding to review feedback promptly.
4. Site Preparation and Foundation Work — Once permits are approved, the build starts. This involves leveling and prepping the ground, pouring the concrete foundation, and running initial plumbing and electrical conduits.
5. Structural Framing and Weatherproofing — Walls and roof systems go up followed by weatherproofing and exterior finish materials. During this step, the ADU takes its visible shape.
6. MEP Systems Rough-In — Skilled tradespeople install the water supply, drain lines, and electrical panel that make the ADU operationally complete. Inspections are completed at required milestones throughout ADU construction.
7. Interior Finishing and Final Inspections — Flooring, cabinetry, fixtures, paint are placed and inspected to your specifications. A last official inspection confirms the unit is code-compliant and the unit is officially approved 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 are a homeowner with available square footage under zoning rules, you're already in a good starting place. Homeowners wanting to add a revenue stream through rental are among the most common ADU construction clients, along with families supporting elderly parents.

ADU construction also suits someone who needs a dedicated professional workspace and wants a detached creative or business space that remains away from your family's daily life. Real estate-minded homeowners who are building a portfolio are also prime candidates for ADU construction, since the long-term value is proven.

Situations where ADU construction may not be the best first step include lots that are below minimum size thresholds. Very small lots or properties with easements may face additional constraints. Our team can assess each property on its own merits to advise you on what's feasible.

ADU Construction FAQ

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

The total process for ADU construction typically ranges from six to fourteen months, influenced by the type of unit being built and local permitting timelines. The approval phase alone can take several months in San Jose, so planning ahead matters. Smaller detached units can move faster, while larger new construction ADUs fall toward the upper Brother & Brother Builders adu construction end of the timeline.

What does ADU construction typically cost?

Budget requirements differ based on project complexity and finishes selected. In the San Jose area, ADU construction commonly costs $150,000 to $400,000 or more for a detached new build. Attached ADU additions often come in under, sometimes between $75,000 and $140,000. A detailed estimate can only be developed after a formal feasibility evaluation.

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 typically less disruptive, since work happens away from the main house. Garage conversions or attached additions may involve some shared wall work during key milestones. Brother & Brother Builders keeps you informed about upcoming work and timelines.

Do I need to leave my home during ADU construction?

For the majority of homeowners, you do not need to vacate your primary residence during ADU construction. The vast majority of projects are designed so that you stay in your primary unit throughout the build. There are edge cases if major utility upgrades affect the main house in ways that require short-term access disruption. Our construction supervisors will flag these situations during the planning phase.

How long will an ADU built through professional ADU construction remain in good condition?

A well-built ADU should last as long as any standard residential structure — indefinitely with proper upkeep. How long it lasts comes down to the systems installed, 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 ensure lasting performance.

ADU Construction for Local Homeowners

Residential areas across San Jose present a diverse mix of property types that are well suited for ADU construction. Residents in the Rose Garden district frequently see their parcels are well configured for ADU builds. Communities around the Capitol Expressway corridor are seeing more homeowners add secondary units as multigenerational living becomes more common. From neighborhoods near the Guadalupe River Park corridor to those near Branham Lane, our team knows the permitting landscape well.

Local regulatory bodies in this area follows defined procedures for ADU construction that experienced builders know well. Proximity to transit corridors can impact the design approach for a given ADU project. Our team's knowledge of the San Jose permitting environment means smoother project delivery from the first meeting to the final inspection.

Start Your ADU Construction Consultation Today

When you want to explore what an ADU could look like on your lot, Brother & Brother Builders is ready to guide you. We bring proven skills in ADU construction for many different project types — from simple garage conversions to large custom detached cottages. The process begins with a comprehensive site assessment where we learn what you're trying to accomplish and share clear expectations of what the project will involve.

Get in touch with our office to schedule a site visit. Whether you're in the early stages of planning, our team is happy to answer questions, share examples of our work and help you take the next step. Building an ADU is a major 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