Unlock New Space with Professional ADU Construction
Families in San Jose, CA are realizing that adding an accessory dwelling unit is one of the most practical investments they can make. ADU construction creates a versatile new living space on your existing property — whether you want to house a family member. Brother & Brother Builders has helped hundreds of local homeowners turn these plans to life with skill and care.
The demand for ADU construction has increased significantly in recent years, and it's easy to understand why. California state law has streamlined permitting for homeowners to construct these secondary units, and local municipalities like San Jose have supported the trend as a way to expand the housing supply. If you're planning 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 bring years of hands-on experience to every ADU construction job. Our team is familiar with city and county requirements, the engineering requirements, and the planning steps that make an ADU functional. 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 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 exists on the same lot as a primary residence. ADU construction comes in multiple configurations, including detached backyard units, attached additions, garage conversions, and even basement or interior conversions.
Mechanically, the process begins with a comprehensive review of your lot, where our builders evaluate property boundaries, available square footage, and infrastructure capacity. From there, architectural drawings are prepared and submitted to the local building department. Once permits are secured, ADU construction enters the physical build phase — which covers everything from foundational work, framing, roofing, plumbing, electrical, insulation. The result is a fully functional living unit adjacent to or detached from your main home.
The difference between a good and a great ADU build is the depth of planning at every stage. Components should be specified to match the primary home's aesthetic. 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 Benefits ADU Construction
- Boosted Home Equity — ADU construction delivers real market value to your property, often returning more than the build cost when it's time to sell.
- Revenue Generation — A completed ADU may be listed as a long-term rental or short-term vacation unit, generating steady monthly revenue for the homeowner.
- Multi-Generational Living — ADU construction gives aging parents a self-contained residence without leaving the property.
- Design Flexibility — From modern studio layouts, ADU construction can be tailored to the intended occupant's lifestyle.
- Faster Permitting in California — Recent state legislation has cut down the permitting obstacles associated with ADU construction, resulting in a timeline that is faster and more affordable than ever before.
- Responsible Property Development — Building an ADU uses your existing lot instead of requiring new development, which supports broader sustainability goals.
- Separate Entrances and Spaces — Unlike a bedroom addition, ADU construction produces a fully self-contained unit where residents have their own space.
- Durable Return on Investment — 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
- Property Walkthrough and Feasibility Check — Our builders assess your property to evaluate setbacks, lot coverage limits, and utility connections. This phase answers exactly what ADU types will work before any time is invested in drawings.
- Blueprint Development and Layout Design — Licensed architects and designers create detailed floor plans based on your goals. Layouts are carefully considered to create practical, comfortable living.
- Permit Submission and Municipal Review — ADU construction in San Jose demands documentation to the city's building department for sign-off and verification. We manage this entire process on your behalf, addressing any city comments promptly.
- Ground Prep and Structural Base — Once permits are issued, on-site work kicks off. This includes grading the site, pouring the concrete foundation, and establishing utility connections.
- Framing, Roofing, and Exterior Work — The structural frame is erected followed by insulation, sheathing, and exterior cladding. At this stage, the ADU transforms from a concept to a building.
- Mechanical, Electrical, and Plumbing Installation — Skilled tradespeople install the water supply, drain lines, and electrical panel that make the ADU operationally complete. Inspections are completed at designated stages throughout ADU construction.
- Interior Finishing and Final Inspections — Countertops, hardware, finishes, and fixtures are installed and finished to your specifications. A closing municipal review confirms the unit is code-compliant and the ADU is ready for use.
Who Is a Right Fit for ADU Construction?
Property owners who are best suited from ADU construction typically fall into a few recognizable groups. If you have a residential property with a backyard, garage, or basement that could be converted, you're already a strong candidate. Homeowners hoping to offset mortgage costs through rental are among the most motivated ADU construction clients, along with families supporting elderly parents.
Another strong candidate is someone who works from home and wants a detached creative or business space that remains away 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.
Homeowners who may want to pause and evaluate include properties with significant setback limitations. Sites with underground infrastructure conflicts may need a modified approach. Our team can assess each property case by case to recommend the right path forward.
ADU Construction Frequently Asked Questions
How long does ADU construction usually take from start to finish?
The complete duration for ADU construction typically ranges from 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 multi-room detached cottages 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. In the San Jose area, ADU construction generally falls between $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 formal feasibility evaluation.
Is ADU construction intrusive while it's underway?
The day-to-day impact depends on the project's location on your property. Standalone ADU projects are usually easier to live alongside, since the crew operates at a distance from your living areas. Projects that connect to the main structure may create short-term inconveniences during key milestones. Brother & Brother Builders keeps you informed about any phases that may affect your routine.
Do I need to leave my home during ADU construction?
Generally speaking, you are not required to vacate your primary residence during ADU construction. Most builds are designed so that you remain on the property throughout the build. Certain situations could require a brief departure if significant structural connections require temporary shutoffs in ways that require short-term access disruption. Our project managers will flag these situations during the pre-construction consultation.
How long will an ADU built through professional ADU construction hold up?
A well-built ADU should last as long as the main residence — indefinitely with proper upkeep. Durability depends to the quality of materials used, whether the unit is properly cared for, and whether systems like roofing and plumbing are serviced regularly. Brother & Brother Builders specifies commercial-grade materials and comply with all local building codes to ensure lasting performance.
ADU Construction for San Jose Homeowners
San Jose's neighborhoods offer a variety of property types that are ideally positioned for ADU construction. Property owners get more info near the Almaden Valley area often discover their properties are well configured for ADU builds. Communities around the Capitol Expressway corridor have seen growing ADU activity as multigenerational living becomes more common. If you're located closer to Evergreen, our team has project experience in the area.
The City of San Jose's building department applies particular standards 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 this region's building landscape means smoother project delivery from design through the final walkthrough.
Start Your ADU Construction Planning Session Today
When you want to move forward with ADU construction, Brother & Brother Builders is the team to call. Our builders provide licensed expertise in ADU construction across a wide range of project types — from modest studio builds to multi-room backyard residences. The process begins with a comprehensive site assessment where we learn what you're trying to accomplish and share clear expectations of what's achievable.
Contact Brother & Brother Builders to begin the conversation. Whether you're in the early stages of planning, our team is happy to walk through your options, review completed projects and help you take the next step. Building an ADU is a major decision — and our goal is to ensure it delivers real value.
Brother & Brother Builders | 3109 Stevens Creek Boulevard | San Jose CA 95117 | (888) 412-2632