Expand Your Home with Expert 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 flexible 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 precision and integrity.
The interest in ADU construction has increased significantly in recent years, and it's not hard to see 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 increase density responsibly. If you're planning a detached backyard cottage, a garage conversion, or an attached addition, ADU construction gives you more control over how your property serves your household.
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 details, and the aesthetic decisions that make an ADU truly livable. When you're ready to explore what ADU construction could look like on your property, this guide covers everything you need to know.
What Is an ADU Build?
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 — equipped with a kitchen, bathroom, sleeping area, and its own access point — that exists on the same lot as a primary residence. ADU construction includes various structural types, including detached backyard units, attached additions, garage conversions, and even below-grade dwelling units.
Mechanically, the work starts with a comprehensive review of your lot, where our team evaluate setbacks, zoning, utility access, and structural feasibility. From there, design plans are prepared and submitted to the city for permit approval. Once the paperwork is cleared, ADU construction transitions to 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 attached to or separate from your main home.
What separates excellent ADU construction from an average project is the depth of planning at every stage. Materials must be selected to align with the neighborhood's character. Systems like HVAC and drainage must be built for long-term residential demand. Brother & Brother Builders handles every ADU construction job with the same technical discipline we bring to full custom home projects.
Key Advantages ADU Construction
- Increased Property Value — ADU construction adds measurable 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, providing a consistent income stream for the homeowner.
- Space for Loved Ones — ADU construction gives aging parents a self-contained residence without leaving the property.
- Customization Options — From open-plan one-bedrooms, ADU construction is adaptable to your household's priorities.
- Faster Permitting in California — Recent state legislation has minimized the permitting obstacles associated with ADU construction, creating a path that is faster and more cost-efficient than ever before.
- Sustainable Land Use — Building an ADU works within your current footprint instead of expanding urban sprawl, which supports broader sustainability goals.
- Separate Entrances and Spaces — Unlike a bedroom addition, ADU construction produces a fully self-contained unit where occupants have full privacy.
- Long-Term Investment Security — A well-built ADU remains an asset for decades, providing both usable housing and equity growth.
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 stage clarifies exactly what's possible before any time is invested in drawings.
- Architectural Drafting and Space Planning — Experienced draftspeople create precise architectural drawings based on your goals. Space is thoughtfully allocated to optimize daily use.
- Filing for Building Permits — ADU construction in San Jose requires submitting plans to the city's building department for review and approval. Our team handles all submissions on your behalf, addressing any city comments promptly.
- Excavation and Foundation Installation — Once permits are approved, on-site work kicks off. This involves leveling and prepping the ground, pouring the concrete foundation, and running initial plumbing and electrical conduits.
- Shell Construction and Exterior Finishing — Framing is completed followed by weatherproofing and exterior finish materials. At this stage, the ADU becomes recognizable as a structure.
- MEP Systems Rough-In — Skilled tradespeople install the heating, cooling, drainage, and power infrastructure that make the ADU fully functional. Inspections are completed at required milestones throughout ADU construction.
- Finishes, Fixtures, and Final Walkthrough — Trim, appliances, tile, and lighting are placed and inspected to the approved plan. A last official inspection issues the certificate of occupancy and your new space is cleared for use.
Who Is a Good Candidate for ADU Construction?
People who see the greatest return from ADU construction generally fit within a few recognizable groups. If you have a residential property with enough lot space to meet setback requirements, you're already 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 navigating multigenerational living situations.
ADU construction also suits someone who runs a small business and wants a separate office or studio space that is distinct from your family's daily life. Property investors and rental owners who want to maximize their land are also a natural fit for ADU construction, since rental income frequently offsets build costs.
Situations where ADU construction may not be the best first step include lots that are below minimum size thresholds. Very small lots or properties with easements may need a modified approach. Our experts will evaluate each property case by case to provide realistic options.
ADU Construction FAQ
How long does ADU construction generally take from start to finish?
The total process for ADU construction usually runs between six to fourteen months, based on the project scope and how quickly approvals come through. City review on its own can take several months in San Jose, so beginning the process sooner rather than later is wise. Simpler garage conversions can move faster, while multi-room detached cottages fall toward the upper end of the timeline.
What does ADU construction usually run in terms of budget?
Budget requirements differ based on project complexity and finishes selected. Locally, ADU construction commonly costs $150,000 to $400,000 or more for a standalone backyard unit. Attached ADU additions tend to cost less, sometimes in the $80,000 to $150,000 range. A precise cost projection can only be given after completing a thorough property review.
Is ADU construction difficult to live through while it's underway?
The day-to-day impact depends on whether you're converting existing space or building new. Detached backyard builds are typically less disruptive, since work happens away from the main house. Projects that connect to the main structure may require temporary access during specific stages like framing or MEP rough-in. Brother & Brother Builders keeps you informed about upcoming work and timelines.
Do I need to leave my home during ADU construction?
For the majority of homeowners, you won't have to vacate your main home during ADU more info construction. Most builds are structured to allow you remain on the property throughout the build. Certain situations could require a brief departure 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 kickoff meeting.
How long will an ADU built through professional ADU construction hold up?
An ADU constructed with quality materials can be expected to last as long as any standard residential structure — often several decades with routine maintenance. How long it lasts comes down to the quality of materials used, how consistently minor repairs are addressed, and whether systems like roofing and plumbing are serviced regularly. Brother & Brother Builders specifies residential-grade products rated for longevity and comply with all local building codes to ensure lasting performance.
ADU Construction for Local Homeowners
The communities throughout San Jose provide a variety of property types that are ideally positioned for ADU construction. Residents in the Rose Garden district have found their lots accommodate detached backyard units nicely. Communities around the Capitol Expressway corridor are seeing more homeowners add secondary units as housing demand rises. If you're located closer to Evergreen, our team has likely worked nearby.
San Jose's permitting office applies particular standards for ADU construction that experienced builders know well. Proximity to transit corridors can influence utility connection requirements for a given ADU project. Our familiarity with these local conditions means smoother project delivery from the first meeting to the final inspection.
Schedule Your ADU Construction Assessment Today
If you're ready to move forward with ADU construction, Brother & Brother Builders is the team to call. Our builders provide licensed expertise in ADU construction for many different project types — from modest studio builds to large custom detached cottages. The process begins with a comprehensive site assessment where we listen to your goals and provide an honest assessment of what's achievable.
Reach out to our team 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 make sure you feel confident before committing. ADU construction is a significant investment — and we're committed to helping you get it right.
Brother & Brother Builders | 3109 Stevens Creek Boulevard | San Jose CA 95117 | (888) 412-2632