Unlock New Space with Expert ADU Construction
Families in San Jose, CA are finding that adding an accessory dwelling unit is one of the most practical investments they can make. ADU construction provides 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 turn these plans to life with precision and integrity.
The interest in ADU construction has surged in recent years, and it's easy to understand why. California state law has simplified the process for homeowners to construct these secondary units, and local municipalities like San Jose have embraced 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 offers greater 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 knows the San Jose building codes, the engineering considerations, 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 covers everything you need to know.
What Is an ADU Build?
ADU construction involves the process of designing, permitting, and building an accessory dwelling unit on a residential property. An accessory dwelling unit is a self-contained living space — including a kitchen, bathroom, sleeping area, and its own access point — 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 detailed site assessment, where our professionals evaluate lot dimensions, existing structures, soil conditions, and local code requirements. From there, architectural drawings are prepared and submitted to the local building department. Once approvals are in place, ADU construction enters the physical build phase — which covers everything from foundational work, framing, mechanical systems, weatherproofing, and interior finishing. The result is a completely finished living unit attached to or separate from your main home.
What separates excellent ADU construction from an average project is the attention to detail at every stage. Products need to be chosen to match the primary home's aesthetic. Systems like plumbing and electrical must be sized for independent daily use. Brother & Brother Builders approaches every build with the same high standards we bring to full custom home projects.
Key Advantages ADU Construction
- Boosted Home Equity — 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, creating ongoing passive income for the homeowner.
- Space for Loved Ones — ADU construction offers family members a comfortable home of their own without leaving the property.
- Customization Options — From open-plan one-bedrooms, ADU construction is adaptable to your specific needs.
- Streamlined Approval Process — Recent state legislation has minimized the barriers and delays associated with ADU construction, resulting in a timeline that is faster and more affordable 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 tenants live autonomously.
- Long-Term Investment Security — A well-built ADU continues to produce returns for decades, providing both functional space and financial upside.
The ADU Construction Process Step by Step
- Site Evaluation and Zoning Analysis — Our builders assess your property to evaluate setbacks, lot coverage limits, and utility connections. This stage clarifies exactly what's possible before any money is spent on design.
- Architectural Drafting and Space Planning — Experienced draftspeople create detailed floor plans tailored to your needs. Every square foot is planned 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, responding to review feedback promptly.
- Site Preparation and Foundation Work — Once permits are granted, physical construction begins. This includes grading the site, pouring the concrete foundation, and establishing utility connections.
- Structural Framing and Weatherproofing — The structural frame is erected followed by roofing, siding, windows, and exterior doors. During this step, the ADU becomes recognizable as a structure.
- Interior Systems and Infrastructure — Certified technicians install the heating, cooling, drainage, and power infrastructure that make the ADU fully functional. Inspections are completed at designated stages throughout ADU construction.
- Interior Completion and City Sign-Off — Flooring, cabinetry, fixtures, paint are fitted and completed to the approved plan. A closing municipal review issues the certificate of occupancy and the ADU is ready for use.
Who Is a Strong Candidate for ADU Construction?
Property owners who are best suited from ADU construction generally fit within a few clear categories. If you own a single-family home with a backyard, garage, or basement that could be converted, 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 candidate is someone who works from home and wants a separate office or studio space that remains away from your family's daily life. Real estate-minded homeowners who want to maximize their land are also a natural fit for ADU check here construction, since the long-term value is proven.
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 face additional constraints. Brother & Brother Builders reviews each property individually and honestly to advise you on what's feasible.
ADU Construction Common Questions Answered
How long does ADU construction generally take from start to finish?
The total process for ADU construction commonly spans six to fourteen months, based on the project scope and how quickly approvals come through. Permitting alone can take several months in San Jose, so planning ahead matters. Smaller detached units can move faster, while multi-room detached cottages take longer to complete.
What does ADU construction usually run in terms of budget?
Costs vary widely based on the type and size of the ADU. In the San Jose area, ADU construction commonly costs $150,000 to $400,000 or more for a fully custom construction. Interior conversion projects tend to cost less, sometimes in the $80,000 to $150,000 range. An accurate budget can only be produced following a full site assessment.
Is ADU construction difficult to live through while it's underway?
How much the build affects daily life depends on the project's location on your property. New construction in the rear yard are generally the least intrusive, since the crew operates at a distance from your living areas. Projects that connect to the main structure may require temporary access during certain phases of construction. We provide advance notice about any phases that may affect your routine.
Do I need to vacate the property during ADU construction?
In most cases, you won't have to vacate your house during ADU construction. Most builds are structured to allow you remain on the property throughout the build. Exceptions may arise if major utility upgrades affect the main house in ways that briefly affect habitability. Our project managers will discuss these scenarios during the kickoff meeting.
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 your primary home — often several decades with routine maintenance. Longevity is tied to the standard of construction, whether the unit is properly cared for, and if mechanical components are maintained on schedule. We select residential-grade products rated for longevity and build to current California residential standards to protect your investment for the long haul.
ADU Construction for San Jose 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 frequently see their parcels accommodate detached backyard units nicely. The Berryessa area have seen growing ADU activity as housing demand rises. Whether your property is near downtown San Jose, our team has likely worked nearby.
Local regulatory bodies in this area applies particular standards for ADU construction that our team navigates routinely. Proximity to transit corridors can affect how quickly permits are approved for a given ADU project. Our familiarity with this region's building landscape means smoother project delivery from the first meeting to the final inspection.
Book Your ADU Construction Consultation 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 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 share clear expectations of what ADU construction on your property will look like.
Get in touch with our office to set up your consultation. Even if you're just exploring the idea, we enjoy answer questions, share examples of our work and give you the clarity you need to move forward. 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