Expand Your Home with Expert 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 opens the door to a powerful new living space on your existing property — whether you want to house a family member. Brother & Brother Builders has guided hundreds of local homeowners turn these plans to life with precision and transparency.
The interest in ADU construction has surged in recent years, and it's easy to understand why. California state law now makes it easier for homeowners to construct these secondary units, and local municipalities like San Jose have encouraged the trend as a way to address housing needs. Whether you want to build a detached backyard cottage, a garage conversion, or an attached addition, ADU construction offers greater control over how your property works.
At Brother & Brother Builders, we apply deep hands-on experience to every ADU construction job. Our team understands the local permitting process, the engineering requirements, and the design choices that make an ADU functional. When you're ready to explore what ADU construction could look like on your property, this guide explains everything you need to know.
What Is the ADU Construction Process?
ADU construction involves 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 — featuring a kitchen, bathroom, sleeping area, and its own access point — that sits on the same property 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, everything kicks off with a thorough property evaluation, where our team evaluate setbacks, zoning, utility access, and structural feasibility. From there, architectural drawings are prepared and submitted to the local building department. Once the paperwork is cleared, 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.
The difference between a good and a great ADU build is the depth of planning at every stage. Materials must be selected to complement the existing structure. Systems like HVAC and drainage must be built for long-term residential demand. Brother & Brother Builders treats each project with the same high standards we use on major custom home projects.
Key Reasons to Choose ADU Construction
- Increased Property Value — 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.
- Housing for Extended Family — ADU construction gives aging parents a private, independent living space without losing proximity to the family.
- Design Flexibility — From two-bedroom configurations, ADU construction may be customized to your household's priorities.
- Simplified Regulatory Path — Recent state legislation has reduced the permitting obstacles associated with ADU construction, making the process that is faster and more affordable than ever before.
- Sustainable Land Use — Building an ADU works within your current footprint instead of requiring new development, which aligns with sustainability goals.
- Privacy for All Residents — Unlike a bedroom addition, ADU construction creates a truly separate unit where tenants live autonomously.
- Long-Term Investment Security — A well-built ADU holds its value for many years and generates both usable housing and equity growth.
The ADU Construction Procedure Step by Step
- Initial Property Assessment and Feasibility Review — Our experts review your property to analyze zoning rules, slope conditions, and available square footage. This stage clarifies exactly what ADU types will work before any time is invested in drawings.
- Custom Design and Architectural Planning — Our design team create precise architectural drawings tailored to your needs. Layouts are carefully considered to create practical, comfortable living.
- Permitting and City Approval — ADU construction in San Jose requires submitting plans to the city's building department for sign-off and verification. Brother & Brother Builders coordinates the permitting on your behalf, responding to review feedback promptly.
- Excavation and Foundation Installation — Once permits are granted, on-site work kicks off. This involves leveling and prepping the ground, completing foundation work, and running initial plumbing and electrical conduits.
- Framing, Roofing, and Exterior Work — Walls and roof systems go up followed by insulation, sheathing, and exterior cladding. During this step, the ADU becomes recognizable as a structure.
- Interior Systems and Infrastructure — Certified technicians install the plumbing lines, electrical wiring, and HVAC systems that make the ADU fully functional. Inspections are completed at each code checkpoint throughout ADU construction.
- Finishes, Fixtures, and Final Walkthrough — Flooring, cabinetry, fixtures, paint are installed and finished to your specifications. A final city inspection confirms the unit is code-compliant and your new space is cleared for use.
Who Is a Good Candidate 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 available square footage under zoning rules, 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 accommodating adult children who need housing.
You may also be someone who works from home and wants a detached creative or business space that remains away from your family's daily life. Real more info 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 properties with significant setback limitations. Very small lots or properties with easements may face additional constraints. Our team can assess each property on its own merits to advise you on what's feasible.
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, influenced by the type of unit being built and local permitting timelines. 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. Simpler garage 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?
Costs vary widely 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 detached new build. Garage conversions are generally priced lower, sometimes starting around $80,000 depending on scope. A detailed estimate can only be given after completing a thorough property review.
Is ADU construction disruptive while it's underway?
The level of disruption depends on where the ADU is being built. New construction in the rear yard are typically less disruptive, since the construction zone is separate. Projects that connect to the main structure may involve some shared wall work during specific stages like framing or MEP rough-in. Our team communicates clearly about what to expect at each stage.
Do I need to vacate the property during ADU construction?
In most cases, you won't have to vacate your primary residence during ADU construction. Most builds are structured to allow you stay in your primary unit throughout the build. There are edge cases if significant structural connections require temporary shutoffs in ways that require short-term access disruption. Our project managers will discuss these scenarios during the pre-construction consultation.
How long will an ADU built through professional ADU construction hold up?
Any ADU built to code with professional oversight is designed to last as long as your primary home — typically 50 years or more. How long it lasts comes down to the standard of construction, how well routine maintenance is performed, and how proactively issues are resolved over time. Brother & Brother Builders specifies commercial-grade materials and comply with all local building codes to ensure lasting performance.
ADU Construction for Local Homeowners
Residential areas across San Jose present a variety of property types that are well suited for ADU construction. Property owners near the Almaden Valley area have found their lots accommodate detached backyard units nicely. Communities around the Capitol Expressway corridor are seeing more homeowners add secondary units as multigenerational living becomes more common. From neighborhoods near the Guadalupe River Park corridor to those near Branham Lane, our team has project experience in the area.
San Jose's permitting office follows defined procedures for ADU construction that require a builder familiar with local expectations. Proximity to transit corridors can impact the design approach for a given ADU project. Our familiarity with this region's building landscape means fewer surprises from the first meeting to the final inspection.
Book Your ADU Construction Planning Session Today
If you're ready to move forward with ADU construction, Brother & Brother Builders is here to help. We bring licensed expertise in ADU construction across a wide range of project types — from simple garage conversions to fully independent secondary homes. Our approach opens with a thorough and honest property review where we learn what you're trying to accomplish and provide an honest assessment of what the project will involve.
Get in touch with our office to begin the conversation. No matter where you are in the decision-making process, our team is happy to walk through your options, review completed projects 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