Brother & Brother Builders

Unlock New Space with Professional ADU Construction

Homeowners across 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 powerful 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 skill and transparency.

The popularity of 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 address housing needs. 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 functions.

At Brother & Brother Builders, we draw on extensive hands-on experience to every ADU construction job. Our team understands the local permitting process, the engineering requirements, and the planning steps that make an ADU truly livable. When you're ready to explore what ADU construction could do 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 self-contained 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 basement or interior conversions.

Mechanically, everything kicks off with a detailed site assessment, where our professionals evaluate property boundaries, available square footage, and infrastructure capacity. From there, architectural drawings are prepared and submitted to the relevant municipal authority. Once approvals are in place, ADU construction moves into the physical build phase — which covers everything from foundational work, framing, mechanical systems, weatherproofing, and interior finishing. The result is a move-in-ready living unit connected to or independent of your main home.

What separates excellent ADU construction from an average project is the level of craftsmanship at every stage. Products need to be chosen to match the primary home's aesthetic. Systems like HVAC and drainage must be sized for independent daily use. Brother & Brother Builders treats each project with the same professional rigor we apply to large-scale custom home projects.

Key Benefits ADU Construction

• Higher Resale Potential — ADU construction contributes significant market value to your property, often increasing appraised value substantially when it's time to sell.
• Revenue Generation — A completed ADU is leasable as a long-term rental or short-term vacation unit, generating steady monthly revenue for the homeowner.
• Space for Loved Ones — ADU construction offers family members a self-contained residence without moving to another neighborhood.
• Personalized Layouts — From two-bedroom configurations, ADU construction is adaptable to the intended occupant's lifestyle.
• Streamlined Approval Process — Recent state legislation has cut down the permitting obstacles associated with ADU construction, making the process that is faster and more affordable than ever before.
• Efficient Use of Your Lot — Building an ADU works within your current footprint instead of requiring new development, which contributes to sustainability goals.
• Separate Entrances and Spaces — Unlike a bedroom addition, ADU construction creates a truly separate unit where tenants live autonomously.
• Durable Return on Investment — A well-built ADU holds its value for the long haul by offering both livable square footage and monetary benefit.

The ADU Construction Process Step by Step

1. Property Walkthrough and Feasibility Check — Our experts review your property to analyze zoning rules, slope conditions, and available square footage. This step tells you exactly what's possible before any time is invested in drawings.
2. Custom Design and Architectural Planning — Our design team create detailed floor plans tailored to your needs. Every square foot is planned to create practical, comfortable living.
3. Permit Submission and Municipal Review — ADU construction in San Jose requires submitting plans to the city's building department for sign-off and verification. Brother & Brother Builders coordinates the permitting on your behalf, responding to review feedback promptly.
4. Site Preparation and Foundation Work — Once permits are granted, physical construction begins. This involves leveling and prepping the ground, pouring the concrete foundation, and establishing utility connections.
5. Shell Construction and Exterior Finishing — Walls and roof systems go up followed by insulation, sheathing, and exterior cladding. At this stage, the ADU takes its visible shape.
6. Mechanical, Electrical, and Plumbing Installation — Skilled tradespeople install the water supply, drain lines, and electrical panel that make the ADU fully functional. Inspections are completed at designated stages throughout ADU construction.
7. Finishes, Fixtures, and Final Walkthrough — Countertops, hardware, finishes, and fixtures are installed and finished to the approved plan. A last official inspection grants legal occupancy status and the unit is officially approved for use.

Who Is a Strong 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 available square footage under zoning rules, you're already in a good starting place. Homeowners looking to generate income through rental are among the most financially driven ADU construction clients, along with families supporting elderly parents.

You may also be someone who runs a small business and wants a detached creative or business space that doesn't interfere with your family's daily life. Landlords and real estate investors who already own residential properties are also well suited 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. Parcels in historic districts or HOA-restricted communities may need a modified approach. Brother & Brother Builders reviews each property case by case to provide realistic options.

ADU Construction Common Questions Answered

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

The total process for ADU construction usually runs between six to fourteen months, influenced by the type of unit being built and local permitting timelines. City review on its own can take a significant portion of the overall timeline in San Jose, so beginning the process sooner rather than later is wise. Simpler garage conversions may complete more quickly, while larger new construction ADUs fall toward the upper end of the timeline.

What does ADU construction typically cost?

Budget requirements differ based on whether it's a conversion or new construction. 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 in the $80,000 to $150,000 range. A detailed estimate can only be given after completing a thorough property review.

Is ADU construction disruptive 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 work happens away from the main house. Garage conversions or attached additions may involve some shared wall work during key milestones. We provide advance notice about what to expect at each stage.

Do I need to move out during ADU construction?

In most cases, you do not need to vacate your house during ADU construction. Most builds are structured to allow you continue living in the home throughout the process. Certain situations could require a brief departure if major utility upgrades affect the main house in ways that require short-term access disruption. Our project managers will discuss these scenarios during the planning phase.

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

Any ADU built to code with professional oversight can be expected to last as long as the main residence — typically 50 years or more. Longevity is tied to the quality of materials used, how well routine maintenance is performed, and whether systems like roofing and plumbing are serviced regularly. Our builds use high-quality components and comply with all local building codes to deliver a structure that stands the test of time.

ADU Construction for San Jose Homeowners

San Jose's neighborhoods offer a wide range of property types that are ideally positioned for ADU construction. Property owners near the Almaden Valley area often discover their properties are well configured for ADU builds. Neighborhoods near Blossom Hill Road are seeing more homeowners add secondary units as multigenerational living becomes more common. If you're located closer to Evergreen, our team has likely worked nearby.

Local regulatory bodies in this area applies particular standards for ADU construction that our team navigates routinely. Access to infrastructure along thoroughfares like Monterey Road can impact the design approach for a given ADU project. Brother & Brother Builders' experience across the San Jose permitting environment means fewer surprises from kickoff through certificate of occupancy.

Start Your ADU Construction Planning Session Today

Should you be thinking about how to move forward with ADU construction, Brother & Brother Builders is ready to guide you. Our experts offer years of hands-on experience in ADU construction across a wide range of project types — from modest studio builds to fully independent secondary homes. Our approach opens with a comprehensive site assessment where we learn what you're trying to accomplish and share clear expectations of what's achievable.

Contact Brother & click here Brother Builders to set up your consultation. No matter where you are in the decision-making process, we're glad to walk through your options, review completed projects and give you the clarity you need to move forward. ADU construction is a significant investment — 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