Unlock New Space with Quality ADU Construction
Property owners throughout San Jose, CA are realizing that adding an accessory dwelling unit is one of the most rewarding investments they can make. ADU construction creates a versatile new living space on your existing property — whether you want to create a private workspace. Brother & Brother Builders has supported hundreds of local homeowners turn these plans to life with skill and transparency.
The demand for ADU construction has increased significantly 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 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 functions.
At Brother & Brother Builders, we draw on extensive hands-on experience to every ADU construction job. Our team understands the local permitting process, the engineering details, and the planning steps that make an ADU functional. If you've been thinking about what ADU construction could look like on your property, this guide covers everything you need to know.
What Is the ADU Construction Process?
ADU construction refers to the process of designing, permitting, and building an accessory dwelling unit on a residential property. An accessory dwelling unit is a complete living space — including 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 interior space reconfigurations.
Mechanically, everything kicks off with a detailed site assessment, where our professionals evaluate setbacks, zoning, utility access, and structural feasibility. From there, design plans are prepared and submitted to the relevant municipal authority. Once permits are secured, ADU construction transitions to the physical build phase — which covers everything from foundational work, framing, HVAC, drywall, flooring, and exterior finishes. The result is a fully functional living unit adjacent to or detached from your main home.
What sets quality ADU construction apart is the attention to detail at every stage. Materials must be selected to match the primary home's aesthetic. Systems like wiring and water supply must be sized for independent daily use. Brother & Brother Builders approaches every build with the same professional rigor we apply to large-scale custom home projects.
Key Reasons to Choose ADU Construction
- Boosted Home Equity — ADU construction contributes significant market value to your property, often returning more than the build cost when it's time to sell.
- Rental Income Potential — A completed ADU is leasable 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 self-contained residence without leaving the property.
- Customization Options — From modern studio layouts, ADU construction is adaptable to the intended occupant's lifestyle.
- Simplified Regulatory Path — Recent state legislation has reduced the permitting obstacles associated with ADU construction, resulting in a timeline that is faster and less expensive than ever before.
- Responsible Property Development — Building an ADU uses your existing lot instead of requiring new development, which aligns with sustainability goals.
- Separate Entrances and Spaces — Unlike a bedroom addition, ADU construction produces a fully self-contained unit where residents have their own space.
- Long-Term Investment Security — A well-built ADU continues to produce returns for decades, providing both functional space and financial upside.
The ADU Construction Procedure 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 resources go toward planning.
- Custom Design and Architectural Planning — Experienced draftspeople create detailed floor plans based on your goals. Every square foot is planned to maximize function and livability.
- Permitting and City Approval — ADU construction in San Jose involves filing drawings to the city's building department for review and approval. Brother & Brother Builders coordinates the permitting on your behalf, addressing any city comments promptly.
- Site Preparation and Foundation Work — Once permits are approved, the build starts. This includes grading the site, laying the structural base, and setting up utilities.
- Framing, Roofing, and Exterior Work — Walls and roof systems go up followed by roofing, siding, windows, and exterior doors. This phase, the ADU becomes recognizable as a structure.
- Interior Systems and Infrastructure — Skilled tradespeople install the heating, cooling, drainage, and power infrastructure that make the ADU operationally complete. Every system is reviewed at designated stages throughout ADU construction.
- Interior Completion and City Sign-Off — Trim, appliances, tile, and lighting are fitted and completed to your specifications. A last official inspection issues the certificate of occupancy and the ADU is ready for use.
Who Is a Right Fit for ADU Construction?
Property owners who are best suited 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 wanting to add a revenue stream through rental are among the most financially driven ADU construction clients, along with families supporting elderly parents.
You may also be 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 are building a portfolio are also a natural fit for ADU construction, since the long-term value is proven.
Those who should discuss alternatives first include lots that are below minimum size thresholds. Parcels in historic districts or HOA-restricted communities may require additional review. Our experts will evaluate each property case by case to advise you on what's feasible.
ADU Construction Common Questions Answered
How long does ADU construction usually take from start to finish?
The complete duration for ADU construction commonly spans six to fourteen months, based on the project scope and how quickly approvals come through. The approval phase alone can take several months in San Jose, so starting early is important. Smaller detached units can move faster, while custom detached builds require more time.
What does ADU construction typically cost?
Costs vary widely based on project complexity and finishes selected. Locally, ADU construction commonly costs $150,000 to $400,000 or more for a detached new build. Attached ADU additions tend to cost less, adu construction sometimes between $75,000 and $140,000. A precise cost projection can only be developed after 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. Detached backyard builds are typically less disruptive, since work happens away from the main house. Projects that connect to the main structure may involve some shared wall work during certain phases of construction. We provide advance notice about any phases that may affect your routine.
Do I need to leave my home during ADU construction?
Generally speaking, you are not required to vacate your main home during ADU construction. The vast majority of projects are structured to allow you remain on the property throughout the build. Certain situations could require a brief departure if significant structural connections require temporary shutoffs in ways that briefly affect habitability. The team at Brother & Brother Builders will flag these situations during the planning phase.
How long will an ADU built through professional ADU construction remain in good condition?
Any ADU built to code with professional oversight should last as long as any standard residential structure — 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. We select commercial-grade materials and build to current California residential standards to ensure lasting performance.
ADU Construction for San Jose Homeowners
Residential areas across San Jose present a variety of property types that are ideally positioned for ADU construction. Property owners near the Almaden Valley area often discover their properties are well configured for ADU builds. The Berryessa area are increasingly popular for ADU construction as families expand. From neighborhoods near the Guadalupe River Park corridor to those near Branham Lane, our team has project experience in the area.
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 these local conditions means more accurate timelines and budgets from the first meeting to the final inspection.
Schedule Your ADU Construction Planning Session Today
Should you be thinking about how to move forward with ADU construction, Brother & Brother Builders is ready to guide you. Our builders provide licensed expertise in ADU construction across a wide range of project types — from modest studio builds to large custom detached cottages. The process begins with a detailed, no-pressure consultation where we listen to your goals and share clear expectations of what the project will involve.
Reach out to our team to schedule a site visit. Even if you're just exploring the idea, we enjoy answer questions, share examples of our work and help you take the next step. Building an ADU is a major decision — and we want to make sure it's the right one for you.
Brother & Brother Builders | 3109 Stevens Creek Boulevard | San Jose CA 95117 | (888) 412-2632