Expand Your Home with Professional ADU Construction
Families in San Jose, CA are discovering 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 generate rental income. Brother & Brother Builders has guided hundreds of local homeowners see these visions to life with skill and integrity.
The popularity of ADU construction has increased significantly in recent years, and it's easy to understand why. California state law now makes it easier for homeowners to build these secondary units, and local municipalities like San Jose have supported 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 provides increased control over how your property functions.
At Brother & Brother Builders, we draw on extensive hands-on experience to every ADU construction project. Our team understands the local permitting process, the engineering requirements, and the design choices that make an ADU truly livable. If you've been thinking about what ADU construction could mean for your property, this guide explains 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 — equipped with a kitchen, bathroom, sleeping area, and its own entrance — that is located on the same parcel as a primary residence. ADU construction includes various structural types, including detached backyard units, attached additions, garage conversions, and even basement or interior conversions.
Mechanically, everything kicks off with a comprehensive review of your lot, where our professionals evaluate lot dimensions, existing structures, soil conditions, and local code requirements. From there, design plans 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, HVAC, drywall, flooring, and exterior finishes. The result is a fully functional living unit attached to or separate from your main home.
The difference between a good and a great ADU build is the level of craftsmanship at every stage. Components should be specified to complement the existing structure. Systems like HVAC and drainage must be built for long-term residential demand. Brother & Brother Builders approaches every build with the same technical discipline we use on major custom home projects.
Key Reasons to Choose ADU Construction
- Increased Property Value — ADU construction adds measurable market value to your property, often returning more than the build cost when it's time to sell.
- Monthly Cash Flow — A completed ADU may be listed as a long-term rental or short-term vacation unit, providing a consistent income stream for the homeowner.
- Housing for Extended Family — ADU construction gives aging parents a self-contained residence without losing proximity to the family.
- Customization Options — From modern studio layouts, ADU construction is adaptable to your specific needs.
- Simplified Regulatory Path — Recent state legislation has minimized the permitting obstacles associated with ADU construction, making the process that is faster and more cost-efficient than ever before.
- Sustainable Land Use — Building an ADU maximizes the land you already own instead of consuming open land, which aligns with sustainability goals.
- Independent Living Areas — Unlike a bedroom addition, ADU construction creates a truly separate unit where occupants have full privacy.
- Lasting Financial Benefit — A well-built ADU holds its value for decades, providing both usable housing and equity growth.
The ADU Construction Process Step by Step
- Initial Property Assessment and Feasibility Review — Our builders assess your property to determine what type of ADU is allowed and where it can be placed. This stage clarifies exactly what can be built before any time is invested in drawings.
- Custom Design and Architectural Planning — Our design team create precise architectural drawings reflecting your priorities. Space is thoughtfully allocated to maximize function and livability.
- Permitting and City Approval — ADU construction in San Jose requires submitting plans to the city's building department for sign-off and verification. We manage this entire process on your behalf, addressing any city comments promptly.
- Excavation and Foundation Installation — Once permits are approved, the build starts. This includes grading the site, laying the structural base, and running initial plumbing and electrical conduits.
- Shell Construction and Exterior Finishing — The structural frame is erected followed by roofing, siding, windows, and exterior doors. This phase, the ADU takes its visible shape.
- Mechanical, Electrical, and Plumbing Installation — Licensed subcontractors install the heating, cooling, drainage, and power infrastructure that make the ADU operationally complete. Every system is reviewed at designated stages throughout ADU construction.
- Finishes, Fixtures, and Final Walkthrough — Countertops, hardware, finishes, and fixtures are installed and finished to the approved plan. A closing municipal review confirms the unit is code-compliant and the ADU is ready for use.
Who Is a Strong Candidate for ADU Construction?
Homeowners who benefit most from ADU construction often belong to a few common profiles. If you own a single-family home with available square footage under zoning rules, you're already a strong candidate. Homeowners looking to generate income through rental are among the most motivated ADU construction clients, along with families navigating multigenerational living situations.
Another strong candidate is someone who needs a dedicated professional workspace and wants a detached creative or business space that doesn't interfere with your family's daily life. Real estate-minded homeowners who are building a portfolio are also well suited for ADU construction, since the long-term value is proven.
Homeowners who may want to pause and evaluate include sites with unusual utility access challenges. Sites with underground infrastructure conflicts may face additional constraints. Our team can assess each property on its own merits to advise you on what's feasible.
ADU Construction Frequently Asked Questions
How long does ADU construction typically take from start to finish?
The full timeline for ADU construction usually runs between six to fourteen months, based on the project scope and local permitting timelines. City review on its own can take two to four months in San Jose, so planning ahead matters. Straightforward interior conversions can move faster, while larger new construction ADUs take longer to complete.
What does ADU construction typically cost?
Budget requirements differ based on project complexity and finishes selected. In the San Jose area, ADU construction typically ranges from $150,000 to $400,000 or more for a fully custom construction. Attached ADU additions are generally priced lower, sometimes in the $80,000 to $150,000 range. A detailed estimate can only be produced following a thorough property review.
Is ADU construction difficult to live through while it's underway?
The level of disruption depends on where the ADU is being built. Detached backyard builds are typically less disruptive, since work happens away from the main house. Projects that connect to the main structure may create short-term inconveniences during specific stages like framing or MEP rough-in. We provide advance notice about any phases that may affect your routine.
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. Most builds are designed so that you remain on the property throughout the construction timeline. There are edge cases if interior conversion work touches shared systems in ways that require short-term access disruption. 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 remain in good condition?
A well-built ADU is designed to last as long as any standard residential structure — indefinitely with proper upkeep. Durability depends to the systems installed, how well routine maintenance is performed, and how proactively issues are resolved over time. We select residential-grade products rated for longevity and follow all code requirements to ensure lasting performance.
ADU Construction for San Jose Homeowners
Residential areas across San Jose present a diverse mix of property types that are perfectly suited for ADU construction. Property owners near the Almaden Valley area often discover their properties work well for both attached and detached projects. The Berryessa area are seeing more homeowners add secondary units as multigenerational living becomes more common. If you're located closer to Evergreen, our team knows the permitting landscape well.
The City of San Jose's building department has developed specific protocols for ADU construction that experienced builders know well. 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 smoother project delivery from kickoff through certificate of occupancy.
Schedule Your ADU Construction Planning Session Today
Should you be thinking about how to add an ADU to your property, Brother & Brother Builders is the team to call. Our builders provide proven skills in ADU construction including all types of project types — from modest studio builds to multi-room backyard residences. Every project starts with a comprehensive site assessment where we learn what you're trying to accomplish and give you a realistic picture of what the project will involve.
Reach out to our team to schedule a site visit. Whether you're in the early stages of planning, our team is happy to walk through check here your options, review completed projects and give you the clarity you need to move forward. 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