Expand Your Home with Expert ADU Construction
Families in San Jose, CA are discovering that adding an accessory dwelling unit is one of the most rewarding investments they can make. ADU construction provides a flexible new living space on your existing property — whether you want to house a family member. Brother & Brother Builders has supported hundreds of local homeowners see these visions to life with skill and care.
The interest in 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 add these secondary units, and local municipalities like San Jose have encouraged 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 provides increased control over how your property functions.
At Brother & Brother Builders, we apply deep hands-on experience to every ADU construction build. Our team understands the local permitting process, the engineering considerations, 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 will walk you through everything you need to know.
What Is the ADU Construction Process?
ADU construction involves 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 — featuring a kitchen, bathroom, sleeping area, and its own access point — that sits on the same property as a primary residence. ADU construction includes various structural types, including detached backyard units, attached additions, garage conversions, and even interior space reconfigurations.
Mechanically, the work starts with a thorough property evaluation, where our builders evaluate setbacks, zoning, utility access, and structural feasibility. From there, architectural drawings are prepared and submitted to the relevant municipal authority. Once permits are secured, ADU construction transitions to the physical build phase — which encompasses site preparation, framing, roofing, plumbing, electrical, insulation. The result is a move-in-ready living unit connected to or independent of your main home.
The difference between a good and a great ADU build is the depth of planning at every stage. Materials must be selected to align with the neighborhood's character. Systems like plumbing and electrical must be sized for independent daily use. Brother & Brother Builders approaches every build with the same high standards we bring to full custom home projects.
Key Advantages ADU Construction
- Higher Resale Potential — ADU construction delivers real market value to your property, often generating strong equity gains 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.
- Space for Loved Ones — ADU construction offers family members a self-contained residence without leaving the property.
- Design Flexibility — From two-bedroom configurations, ADU construction can be tailored to the intended occupant's lifestyle.
- Streamlined Approval Process — Recent state legislation has cut down the barriers and delays 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 delivers a genuinely independent unit where tenants live autonomously.
- Lasting Financial Benefit — A well-built ADU continues to produce returns for many years and generates both livable square footage and monetary benefit.
The ADU Construction Process Step by Step
- Site Evaluation and Zoning Analysis — Our experts review your property to analyze zoning rules, slope conditions, and available square footage. This phase answers exactly what ADU types will work before any money is spent on design.
- Blueprint Development and Layout Design — Licensed architects and designers create precise architectural drawings reflecting your priorities. Layouts are carefully considered to maximize function and livability.
- Permitting and City Approval — ADU construction in San Jose demands documentation to the city's building department for sign-off and verification. Our team handles all submissions on your behalf, resolving any revision requests promptly.
- Excavation and Foundation Installation — Once permits are issued, physical construction begins. This involves leveling and prepping the ground, pouring the concrete foundation, and establishing utility connections.
- Structural Framing and Weatherproofing — Walls and roof systems go up followed by roofing, siding, windows, and exterior doors. At this stage, the ADU takes its visible shape.
- Interior Systems and Infrastructure — Skilled tradespeople install the heating, cooling, drainage, and power infrastructure that make the ADU operationally complete. Every system is reviewed at each code checkpoint throughout ADU construction.
- Interior Completion and City Sign-Off — Countertops, hardware, finishes, and fixtures are fitted and completed to the agreed design. A final city inspection confirms the unit is code-compliant and the ADU is ready for use.
Who Is a Good Candidate for ADU Construction?
People who see the greatest return from ADU construction generally fit within a few common profiles. If you own a single-family home with a backyard, garage, or basement that could be converted, you're already click here 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.
You may also be someone who runs a small business and wants a private work environment that is distinct from your family's daily life. Landlords and real estate investors who already own residential properties are also prime candidates for ADU construction, since the long-term value is proven.
Those who should discuss alternatives first include sites with unusual utility access challenges. Sites with underground infrastructure conflicts may need a modified approach. Our experts will evaluate each property on its own merits to provide realistic options.
ADU Construction FAQ
How long does ADU construction usually take from start to finish?
The full timeline for ADU construction commonly spans six to fourteen months, depending on design complexity and local permitting timelines. City review on its own can take several months in San Jose, so planning ahead matters. Smaller detached units may complete more quickly, while multi-room detached cottages take longer to complete.
What does ADU construction cost in San Jose?
Costs vary widely based on the type and size of the ADU. For most projects in this region, ADU construction commonly costs $150,000 to $400,000 or more for a detached new build. Attached ADU additions often come in under, sometimes in the $80,000 to $150,000 range. A detailed estimate can only be developed after a thorough property review.
Is ADU construction intrusive while it's underway?
The level of disruption depends on the project's location on your property. Standalone ADU projects are generally the least intrusive, since work happens away from the main house. Garage conversions or attached additions may require temporary access during key milestones. We provide advance notice about upcoming work and timelines.
Do I need to vacate the property during ADU construction?
In most cases, you won't have to vacate your primary residence during ADU construction. The vast majority of projects are structured to allow you continue living in the home throughout the construction timeline. There are edge cases if major utility upgrades affect the main house in ways that temporarily impact livability. Our construction supervisors will walk you through any potential disruptions during the pre-construction consultation.
How long will an ADU built through professional ADU construction hold up?
Any ADU built to code with professional oversight is designed to last as long as the main residence — indefinitely with proper upkeep. How long it lasts comes down to the standard of construction, whether the unit is properly cared for, and how proactively issues are resolved over time. Brother & Brother Builders specifies high-quality components and build to current California residential standards to deliver a structure that stands the test of time.
ADU Construction for San Jose Homeowners
The communities throughout San Jose provide a wide range of property types that are well suited for ADU construction. Property owners near the Almaden Valley area frequently see their parcels work well for both attached and detached projects. Communities around the Capitol Expressway corridor are seeing more homeowners add secondary units as families expand. Whether your property is near downtown San Jose, our team has likely worked nearby.
The City of San Jose's building department 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 affect how quickly permits are approved for a given ADU project. Brother & Brother Builders' experience across this region's building landscape means smoother project delivery from kickoff through certificate of occupancy.
Book Your ADU Construction Planning Session Today
Should you be thinking about how to explore what an ADU could look like on your lot, Brother & Brother Builders is ready to guide you. Our experts offer licensed expertise in ADU construction across a wide range of project types — from modest studio builds to fully independent secondary homes. Our approach opens with a thorough and honest property review where we learn what you're trying to accomplish and provide an honest assessment of what's achievable.
Contact Brother & Brother Builders to set up your consultation. Even if you're just exploring the idea, 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 CA 95117 | (888) 412-2632