Unlock New Space with Expert ADU Construction
Homeowners across San Jose, CA are discovering that adding an accessory dwelling unit is one of the most rewarding investments they can make. ADU construction provides 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 bring these projects to life with skill and transparency.
The popularity of ADU construction has increased significantly in recent years, and it's easy to understand why. California state law has simplified the process for homeowners to build these secondary units, and local municipalities like San Jose have encouraged the trend as a way to address housing needs. 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 is familiar with city and county requirements, the engineering details, and the aesthetic decisions that make an ADU truly livable. If you've been thinking about what ADU construction could do for your property, this guide covers everything you need to know.
What Is an ADU Build?
ADU construction involves 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 — including a kitchen, bathroom, sleeping area, and its own entryway — 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 team evaluate property boundaries, available website square footage, and infrastructure capacity. From there, design plans are prepared and submitted to the city for permit approval. Once permits are secured, ADU construction transitions to the physical build phase — which includes foundation work, framing, HVAC, drywall, flooring, and exterior finishes. The result is a fully functional living unit attached to or separate from your main home.
What separates excellent ADU construction from an average project is the level of craftsmanship at every stage. Components should be specified to complement the existing structure. Systems like HVAC and drainage must be sized for independent daily use. Brother & Brother Builders approaches every build with the same professional rigor we bring to full custom home projects.
Key Advantages ADU Construction
- Boosted Home Equity — ADU construction adds measurable market value to your property, often generating strong equity gains when it's time to sell.
- Revenue Generation — A completed ADU is leasable as a long-term rental or short-term vacation unit, generating steady monthly revenue for the homeowner.
- Space for Loved Ones — ADU construction gives aging parents a self-contained residence without losing proximity to the family.
- Personalized Layouts — From modern studio layouts, ADU construction can be tailored to the intended occupant's lifestyle.
- Faster Permitting in California — Recent state legislation has reduced the red tape associated with ADU construction, creating a path that is faster and more cost-efficient than ever before.
- Responsible Property Development — Building an ADU works within your current footprint instead of consuming open land, which aligns with sustainability goals.
- Privacy for All Residents — Unlike a bedroom addition, ADU construction creates a truly separate unit where tenants live autonomously.
- Durable Return on Investment — A well-built ADU remains an asset for the long haul by offering both livable square footage and monetary benefit.
The ADU Construction Journey Step by Step
- Property Walkthrough and Feasibility Check — Our builders assess your property to determine what type of ADU is allowed and where it can be placed. This phase answers exactly what ADU types will work before any money is spent on design.
- Blueprint Development and Layout Design — Licensed architects and designers create precise architectural drawings reflecting your priorities. Layouts are carefully considered to maximize function and livability.
- Filing for Building Permits — ADU construction in San Jose involves filing drawings to the city's building department for review and approval. We manage this entire process on your behalf, addressing any city comments promptly.
- Excavation and Foundation Installation — Once permits are issued, physical construction begins. This involves leveling and prepping the ground, pouring the concrete foundation, and establishing utility connections.
- Shell Construction and Exterior Finishing — The structural frame is erected followed by roofing, siding, windows, and exterior doors. This phase, the ADU becomes recognizable as a structure.
- MEP Systems Rough-In — Licensed subcontractors install the heating, cooling, drainage, and power infrastructure that make the ADU operationally complete. Every system is reviewed at designated stages throughout ADU construction.
- Finishes, Fixtures, and Final Walkthrough — Trim, appliances, tile, and lighting are installed and finished to the agreed design. A last official inspection confirms the unit is code-compliant and the unit is officially approved for use.
Who Is a Good Candidate for ADU Construction?
People who see the greatest return from ADU construction generally fit within a few common profiles. If you are a homeowner with a backyard, garage, or basement that could be converted, you're already in a good starting place. Homeowners hoping to offset mortgage costs through rental are among the most financially driven ADU construction clients, along with families accommodating adult children who need housing.
You may also be someone who works from home and wants a private work environment that doesn't interfere with your family's daily life. Landlords and real estate investors who are building a portfolio are also prime candidates for ADU construction, since the long-term value is proven.
Homeowners who may want to pause and evaluate include sites with unusual utility access challenges. Very small lots or properties with easements may face additional constraints. Our team can assess each property case by case to advise you on what's feasible.
ADU Construction FAQ
How long does ADU construction typically take from start to finish?
The full timeline for ADU construction typically ranges from six to fourteen months, based on the project scope and city review schedules. The approval phase alone can take two to four months in San Jose, so starting early is important. Smaller detached units may complete more quickly, while multi-room detached cottages require more time.
What does ADU construction cost in San Jose?
Pricing depends on many factors based on whether it's a conversion or new construction. Locally, ADU construction commonly costs $150,000 to $400,000 or more for a fully custom construction. Interior conversion projects often come in under, sometimes starting around $80,000 depending on scope. A detailed estimate can only be developed after a full site assessment.
Is ADU construction intrusive while it's underway?
How much the build affects daily life depends on the project's location on your property. Standalone ADU projects 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 what to expect at each stage.
Do I need to move out during ADU construction?
For the majority of homeowners, you do not need to vacate your main home during ADU construction. The vast majority of projects are designed so that you stay in your primary unit throughout the process. Exceptions may arise if major utility upgrades affect the main house in ways that require short-term access disruption. Our project managers will flag these situations during the pre-construction consultation.
How long will an ADU built through professional ADU construction hold up?
An ADU constructed with quality materials should last as long as your primary home — often several decades with routine maintenance. Longevity is tied to the systems installed, how well routine maintenance is performed, and whether systems like roofing and plumbing are serviced regularly. We select commercial-grade materials and follow all code requirements to protect your investment for the long haul.
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 frequently see their parcels work well for both attached and detached projects. Communities around the Capitol Expressway corridor are increasingly popular for ADU construction as families expand. Whether your property is near downtown San Jose, our team knows the permitting landscape well.
Local regulatory bodies in this area has developed specific protocols for ADU construction that require a builder familiar with local expectations. Proximity to transit corridors can influence utility connection requirements for a given ADU project. Brother & Brother Builders' experience across these local conditions means smoother project delivery from the first meeting to the final inspection.
Start Your ADU Construction Planning Session Today
When you want to explore what an ADU could look like on your lot, Brother & Brother Builders is ready to guide you. Our experts offer years of hands-on experience in ADU construction including all types of project types — from simple garage conversions to fully independent secondary homes. The process begins with a detailed, no-pressure consultation where we learn what you're trying to accomplish and give you a realistic picture of what ADU construction on your property will look like.
Contact Brother & Brother Builders to begin the conversation. No matter where you are in the decision-making process, we're glad to answer questions, share examples of our work and help you take the next step. This type of project is a meaningful commitment — and we're committed to helping you get it right.
Brother & Brother Builders | 3109 Stevens Creek Boulevard | San Jose CA 95117 | (888) 412-2632