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 creates a versatile new living space on your existing property — whether you want to house a family member. Brother & Brother Builders has guided hundreds of local homeowners bring these projects to life with precision 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 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 gives you more control over how your property serves your household.
At Brother & Brother Builders, we apply deep hands-on experience to every ADU construction build. Our team knows the San Jose building codes, the engineering details, and the planning steps that make an ADU truly livable. Should you want to learn about what ADU construction could do for your property, this guide covers everything you need to know.
What Is ADU Construction?
ADU construction involves 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 — featuring a kitchen, bathroom, sleeping area, and its own entrance — that exists on the same lot as a primary residence. ADU construction can take several forms, including detached backyard units, attached additions, garage conversions, and even basement or interior conversions.
Mechanically, the work starts with a thorough property evaluation, where our builders evaluate property boundaries, available square footage, and infrastructure capacity. From there, design plans are prepared and submitted to the city for permit approval. Once approvals are in place, ADU construction enters the physical build phase — which covers everything from foundational work, framing, HVAC, drywall, flooring, and exterior finishes. 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 attention to detail at every stage. Materials must be selected to complement the existing structure. Systems like wiring and water supply must be built for long-term residential demand. Brother & Brother Builders approaches every build with the same technical discipline we apply to large-scale custom home projects.
Key Reasons to Choose ADU Construction
- Higher Resale Potential — ADU construction delivers real market value to your property, often increasing appraised value substantially when it's time to sell.
- Monthly Cash Flow — A completed ADU is leasable as a long-term rental or short-term vacation unit, creating ongoing passive income for the homeowner.
- Housing for Extended Family — ADU construction offers family members a self-contained residence without leaving the property.
- Customization Options — From two-bedroom configurations, ADU construction may be customized to your household's priorities.
- Simplified Regulatory Path — Recent state legislation has minimized the red tape associated with ADU construction, making the process that is faster and less expensive than ever before.
- Responsible Property Development — Building an ADU works within your current footprint 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 residents have their own space.
- Durable Return on Investment — A well-built ADU continues to produce returns for the long haul by offering both functional space and financial upside.
The ADU Construction Journey 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 step tells you exactly what's possible before any money is spent on design.
- Blueprint Development and Layout Design — Our design team create comprehensive blueprints tailored to your needs. Layouts are carefully considered to optimize daily use.
- Permit Submission and Municipal Review — ADU construction in San Jose requires submitting plans to the city's building department for inspection and clearance. Brother & Brother Builders coordinates the permitting on your behalf, addressing any city comments promptly.
- Site Preparation and Foundation Work — Once permits are granted, physical construction begins. This covers land preparation, completing foundation work, and running initial plumbing and electrical conduits.
- Shell Construction and Exterior Finishing — Framing is completed followed by roofing, siding, windows, and exterior doors. This phase, the ADU becomes recognizable as a structure.
- MEP Systems Rough-In — Certified technicians install the plumbing lines, electrical wiring, and HVAC systems that make the ADU fully functional. Inspections are completed at designated stages throughout ADU construction.
- Interior Finishing and Final Inspections — Trim, appliances, tile, and lighting are fitted and completed to the approved plan. A last official inspection confirms the unit is code-compliant and your new space is cleared for use.
Who Is a Strong Candidate for ADU Construction?
Homeowners who benefit most from ADU construction typically fall into a few clear categories. If you are a homeowner with available square footage under zoning rules, you're already in a good starting place. Homeowners looking to generate income through rental are among the most website motivated ADU construction clients, along with families accommodating adult children who need housing.
Another strong candidate is someone who needs a dedicated professional workspace and wants a separate office or studio space that is distinct from your family's daily life. Real estate-minded homeowners who already own residential properties are also well suited for ADU construction, since the return on investment is well-documented.
Those who should discuss alternatives first include lots that are below minimum size thresholds. Sites with underground infrastructure conflicts may face additional constraints. Our experts will evaluate each property case by case to recommend the right path forward.
ADU Construction Frequently Asked Questions
How long does ADU construction generally take from start to finish?
The full timeline for ADU construction typically ranges from six to fourteen months, depending on design complexity and city review schedules. City review on its own can take a significant portion of the overall timeline in San Jose, so planning ahead matters. Simpler garage conversions can move faster, while larger new construction ADUs take longer to complete.
What does ADU construction usually run in terms of budget?
Budget requirements differ based on project complexity and finishes selected. In the San Jose area, ADU construction commonly costs $150,000 to $400,000 or more for a fully custom construction. Attached ADU additions often come in under, sometimes between $75,000 and $140,000. An accurate budget can only be produced following a formal feasibility evaluation.
Is ADU construction intrusive while it's underway?
The level of disruption depends on where the ADU is being built. Detached backyard builds are usually easier to live alongside, since the crew operates at a distance from your living areas. Garage conversions or attached additions may involve some shared wall work during key milestones. Our team communicates clearly about upcoming work and timelines.
Do I need to leave my home during ADU construction?
For the majority of homeowners, you are not required to vacate your primary residence during ADU construction. Most builds are set up to let you remain on the property throughout the construction timeline. There are edge cases if significant structural connections require temporary shutoffs in ways that briefly affect habitability. Our project managers will walk you through any potential disruptions during the planning phase.
How long will an ADU built through professional ADU construction last?
A well-built ADU should last as long as your primary home — typically 50 years or more. Longevity is tied to the systems installed, how well routine maintenance is performed, and if mechanical components are maintained on schedule. Our builds use high-quality components and build to current California residential standards to protect your investment for the long haul.
ADU Construction for Local Homeowners
San Jose's neighborhoods offer a wide range of property types that are ideally positioned for ADU construction. Property owners near the Almaden Valley area have found their lots are well configured for ADU builds. Communities around the Capitol Expressway corridor have seen growing ADU activity as multigenerational living becomes more common. Whether your property is near downtown San Jose, our team knows the permitting landscape well.
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 the San Jose permitting environment means more accurate timelines and budgets from design through the final walkthrough.
Schedule Your ADU Construction Assessment Today
When you want to move forward with ADU construction, Brother & Brother Builders is the team to call. Our builders provide proven skills in ADU construction for many different project types — from modest studio builds to fully independent secondary homes. Every project starts with a thorough and honest property review where we listen to your goals and share clear expectations of what's achievable.
Reach out to our team to schedule a site visit. No matter where you are in the decision-making process, we enjoy answer questions, share examples of our work and help you take the next step. ADU construction is a significant investment — and our goal is to ensure it delivers real value.
Brother & Brother Builders | 3109 Stevens Creek Boulevard | San Jose CA 95117 | (888) 412-2632