Expand Your Home with Quality ADU Construction
Homeowners across San Jose, CA are discovering 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 skill and care.
The popularity of ADU construction has grown rapidly in recent years, and it's not hard to see why. California state law has simplified the process for homeowners to add these secondary units, and local municipalities like San Jose have encouraged 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 gives you more control over how your property functions.
At Brother & Brother Builders, we draw on extensive hands-on experience to every ADU construction project. Our team is familiar with city and county requirements, the engineering considerations, and the aesthetic decisions that make an ADU beautiful. If you've been thinking about what ADU construction could do for your property, this guide covers everything you need to know.
What Is ADU Construction?
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 — featuring a kitchen, bathroom, sleeping area, and its own access point — that sits on the same property as a primary residence. ADU construction can take several forms, including detached backyard units, attached additions, garage conversions, and even below-grade dwelling units.
Mechanically, the work starts with a thorough property evaluation, where our builders evaluate lot dimensions, existing structures, soil conditions, and local code requirements. From there, blueprints are prepared and submitted to the city for permit approval. Once the paperwork is cleared, ADU construction enters the physical build phase — which covers everything from foundational work, framing, roofing, plumbing, electrical, insulation. The result is a completely finished living unit adjacent to or detached from your main home.
What separates excellent ADU construction from an average project is the level of craftsmanship at every stage. Components should be specified to align with the neighborhood's character. Systems like plumbing and electrical must be built for long-term residential demand. Brother & Brother Builders approaches every build with the same high standards we use on major custom home projects.
Key Benefits ADU Construction
- Boosted Home Equity — ADU construction contributes significant market value to your property, often generating strong equity gains when it's time to sell.
- Monthly Cash Flow — 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 private, independent living space without moving to another neighborhood.
- Personalized Layouts — From modern studio layouts, ADU construction can be tailored to your household's priorities.
- Faster Permitting in California — Recent state legislation has cut down the red tape associated with ADU construction, making the process 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 supports broader sustainability goals.
- Privacy for All Residents — Unlike a bedroom addition, ADU construction creates a truly separate unit where occupants have full privacy.
- Lasting Financial Benefit — A well-built ADU remains an asset for many years and generates both livable square footage and monetary benefit.
The ADU Construction Procedure Step by Step
- Property Walkthrough and Feasibility Check — Our experts review your property to evaluate setbacks, lot coverage limits, and utility connections. This stage clarifies exactly what ADU types will work before any time is invested in drawings.
- Blueprint Development and Layout Design — Experienced draftspeople create comprehensive blueprints tailored to your needs. Every square foot is planned to maximize function and livability.
- Filing for Building Permits — ADU construction in San Jose involves filing drawings to the city's building department for inspection and clearance. We manage this entire process on your behalf, addressing any city comments promptly.
- Excavation and Foundation Installation — Once permits are approved, physical construction begins. This includes grading the site, laying the structural base, and setting up utilities.
- Framing, Roofing, and Exterior Work — Walls and roof systems go up followed by roofing, siding, windows, and exterior doors. At this stage, the ADU becomes recognizable as a structure.
- Mechanical, Electrical, and Plumbing Installation — Licensed subcontractors install the plumbing lines, electrical wiring, and HVAC systems that make the ADU fully functional. Every system is reviewed at designated stages throughout ADU construction.
- Interior Finishing and Final Inspections — Flooring, cabinetry, fixtures, paint 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 Right Fit for ADU Construction?
Property owners who are best suited 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 hoping to offset mortgage costs through rental are among the most financially driven ADU construction clients, along with families navigating multigenerational living situations.
ADU construction also suits someone who works from home and wants a separate office or studio space that doesn't interfere with your family's daily life. Property investors and rental owners who want to maximize their land are also prime candidates for ADU construction, since rental income frequently offsets build costs.
Situations where ADU construction may not be the best first step include properties with significant setback limitations. Parcels in historic districts or HOA-restricted communities may face additional constraints. Brother & Brother Builders reviews each property on its own merits to provide realistic options.
ADU Construction Common Questions Answered
How long does ADU construction usually take from start to finish?
The full timeline for ADU construction usually runs between six to fourteen months, depending on design complexity and how quickly approvals come through. The approval phase alone can take a significant portion of the overall timeline in San Jose, so beginning the process sooner rather than later is wise. Straightforward interior conversions often finish in the lower end of the range, while larger new construction ADUs fall toward the upper end of the timeline.
What does ADU construction typically cost?
Pricing depends on many factors based on the type and size of the ADU. Locally, ADU construction commonly costs $150,000 to $400,000 or more for a detached website new build. Garage conversions tend to cost less, sometimes between $75,000 and $140,000. 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 where the ADU is being built. Standalone ADU projects are typically less disruptive, since the construction zone is separate. Garage conversions or attached additions may create short-term inconveniences during certain phases of construction. We provide advance notice about any phases that may affect your routine.
Do I need to move out during ADU construction?
For the majority of homeowners, you won't have to vacate your main home during ADU construction. The vast majority of projects are designed so that you continue living in the home throughout the process. Certain situations could require a brief departure if significant structural connections require temporary shutoffs in ways that temporarily impact livability. Our construction supervisors will flag these situations during the kickoff meeting.
How long will an ADU built through professional ADU construction hold up?
A well-built ADU should last as long as your primary home — indefinitely with proper upkeep. Longevity is tied to the systems installed, whether the unit is properly cared for, and how proactively issues are resolved over time. Our builds use commercial-grade materials and follow all code requirements to ensure lasting performance.
ADU Construction for San Jose Homeowners
The communities throughout San Jose provide a diverse mix of property types that are ideally positioned for ADU construction. Property owners near the Almaden Valley area frequently see their parcels are well configured for ADU builds. The Berryessa area have seen growing ADU activity 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. Access to infrastructure along thoroughfares like Monterey Road can affect how quickly permits are approved for a given ADU project. Brother & Brother Builders' experience across these local conditions means more accurate timelines and budgets from kickoff through certificate of occupancy.
Book Your ADU Construction Planning Session Today
Should you be thinking about how to add an ADU to your property, Brother & Brother Builders is here to help. We bring licensed expertise in ADU construction across a wide range of project types — from small attached additions to fully independent secondary homes. The process begins with a comprehensive site assessment where we listen to your goals and provide an honest assessment of what ADU construction on your property will look like.
Contact Brother & Brother Builders to schedule a site visit. Whether you're in the early stages of planning, we're glad to walk through your options, review completed projects and help you take the next step. This type of project is a meaningful commitment — and we're committed to helping you get it right.
Brother & Brother Builders | 3109 Stevens Creek Boulevard | San Jose CA 95117 | (888) 412-2632