Expand Your Home with Expert ADU Construction
Homeowners across San Jose, CA are realizing that adding an accessory dwelling unit is one of the most practical investments they can make. ADU construction opens the door to a versatile new living space on your existing property — whether you want to house a family member. Brother & Brother Builders has supported hundreds of local homeowners bring these projects to life with craftsmanship and integrity.
The popularity of ADU construction has surged in recent years, and it's no mystery. California state law has simplified the process for homeowners to add these secondary units, and local municipalities like San Jose have embraced the trend as a way to expand the housing supply. If you're planning a detached backyard cottage, a garage conversion, or an attached addition, ADU construction provides increased control over how your property serves your household.
At Brother & Brother Builders, we bring years of hands-on experience to every ADU construction project. Our team understands the local permitting process, the engineering considerations, and the planning steps that make an ADU truly livable. If you've been thinking about what ADU construction could look like on your property, this guide will walk you through everything you need to know.
What Is the ADU Construction Process?
ADU construction describes the process of planning, approving, and constructing an accessory dwelling unit on a residential property. An accessory dwelling unit is a fully independent living space — equipped with 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 professionals evaluate property boundaries, available square footage, and infrastructure capacity. From there, blueprints are prepared and submitted to the relevant municipal authority. Once the paperwork is cleared, ADU construction transitions to the physical build phase — which encompasses site preparation, framing, mechanical systems, weatherproofing, and interior finishing. The result is a fully functional living unit connected to or independent of your main home.
The difference between a good and a great ADU build is the attention to detail 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 professional rigor we apply to large-scale custom home projects.
Key Reasons to Choose ADU Construction
- Higher Resale Potential — ADU construction contributes significant 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 provides adult children a private, independent living space without leaving the property.
- Customization Options — From two-bedroom configurations, ADU construction is adaptable to your specific needs.
- Streamlined Approval Process — Recent state legislation has reduced the red tape associated with ADU construction, resulting in a timeline that is faster and more cost-efficient than ever before.
- Sustainable Land Use — Building an ADU maximizes the land you already own instead of expanding urban sprawl, which contributes to sustainability goals.
- Separate Entrances and Spaces — Unlike a bedroom addition, ADU construction creates a truly separate unit where occupants have full privacy.
- Long-Term Investment Security — A well-built ADU remains an asset for the long haul by offering both usable housing and equity growth.
The ADU Construction Procedure Step by Step
- Property Walkthrough and Feasibility Check — Our builders assess your property to analyze zoning rules, slope conditions, and available square footage. This phase answers exactly what's possible before any time is invested in drawings.
- Custom Design and Architectural Planning — Our design team create detailed floor plans reflecting your priorities. Every square foot is planned to maximize function and livability.
- Permit Submission and Municipal Review — ADU construction in San Jose demands documentation to the city's building department for review and approval. Our team handles all submissions on your behalf, resolving any revision requests promptly.
- Excavation and Foundation Installation — Once permits are granted, on-site work kicks off. This includes grading the site, pouring the concrete foundation, and setting up utilities.
- Structural Framing and Weatherproofing — Framing is completed 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 heating, cooling, drainage, and power infrastructure that make the ADU ready for occupancy. Inspections are completed at each code checkpoint throughout ADU construction.
- Interior Completion and City Sign-Off — Flooring, cabinetry, fixtures, paint are fitted and completed to your specifications. A closing municipal review confirms the unit is code-compliant and your new space is cleared for use.
Who Is a Right Fit for ADU Construction?
People who see the greatest return from ADU construction often belong to a few recognizable groups. If you have a residential property with enough lot space to meet setback requirements, you're already well-positioned. Homeowners wanting to add a revenue stream through rental are among the most financially driven ADU construction clients, along with families accommodating adult children who need housing.
Another strong click here candidate is someone who works from home and wants a detached creative or business space that is distinct from your family's daily life. Property investors and rental owners who already own residential properties are also prime candidates for ADU construction, since the return on investment is well-documented.
Homeowners who may want to pause and evaluate include properties with significant setback limitations. Sites with underground infrastructure conflicts may require additional review. Our team can assess each property individually and honestly to recommend the right path forward.
ADU Construction Common Questions Answered
How long does ADU construction usually take from start to finish?
The complete duration for ADU construction typically ranges from six to fourteen months, influenced by the type of unit being built and how quickly approvals come through. Permitting alone can take a significant portion of the overall timeline in San Jose, so beginning the process sooner rather than later is wise. Smaller detached units may complete more quickly, while larger new construction ADUs require more time.
What does ADU construction usually run in terms of budget?
Budget requirements differ based on whether it's a conversion or new construction. In the San Jose area, ADU construction generally falls between $150,000 to $400,000 or more for a detached new build. Attached ADU additions are generally priced lower, sometimes between $75,000 and $140,000. An accurate budget can only be given after completing a formal feasibility evaluation.
Is ADU construction intrusive while it's underway?
The level of disruption depends on the project's location on your property. New construction in the rear yard are typically less disruptive, since the construction zone is separate. Projects that connect to the main structure may create short-term inconveniences during key milestones. Our team communicates clearly about any phases that may affect your routine.
Do I need to leave my home during ADU construction?
Generally speaking, you do not need to vacate your main home during ADU construction. The vast majority of projects are set up to let you remain on the property throughout the construction timeline. Exceptions may arise if major utility upgrades affect the main house in ways that require short-term access disruption. Our project managers will walk you through any potential disruptions during the pre-construction consultation.
How long will an ADU built through professional ADU construction last?
Any ADU built to code with professional oversight can be expected to last as long as the main residence — typically 50 years or more. Longevity is tied to the systems installed, whether the unit is properly cared for, and if mechanical components are maintained on schedule. Brother & Brother Builders specifies high-quality components and follow all code requirements to ensure lasting performance.
ADU Construction for San Jose Homeowners
The communities throughout San Jose provide a variety of property types that are ideally positioned for ADU construction. Homeowners in the Willow Glen neighborhood often discover their properties work well for both attached and detached projects. Neighborhoods near Blossom Hill Road are increasingly popular for ADU construction as multigenerational living becomes more common. Whether your property is near downtown San Jose, 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 affect how quickly permits are approved for a given ADU project. Brother & Brother Builders' experience across the San Jose permitting environment means fewer surprises from the first meeting to the final inspection.
Schedule Your ADU Construction Consultation Today
If you're ready to move forward with ADU construction, Brother & Brother Builders is here to help. Our experts offer proven skills in ADU construction across a wide range of project types — from simple garage conversions 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 the project will involve.
Reach out to our team to set up your consultation. Whether you're in the early stages of planning, we enjoy discuss timelines, costs, and design possibilities 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