Brother & Brother Builders

Transform Your Property with Expert ADU Construction

Property owners throughout San Jose, CA are realizing that adding an accessory dwelling unit is one of the smartest investments they can make. ADU construction creates a flexible new living space on your existing property — whether you want to generate rental income. Brother & Brother Builders has helped hundreds of local homeowners see these visions to life with precision and transparency.

The demand for ADU construction has grown rapidly in recent years, and it's not hard to see why. California state law now makes it easier for homeowners to add these secondary units, and local municipalities like San Jose have encouraged the trend as a way to expand the housing supply. Whether you're building 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 bring years of hands-on experience to every ADU construction job. Our team understands the local permitting process, the engineering requirements, and the aesthetic decisions that make an ADU truly livable. 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 get more info unit is a complete living space — featuring 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 below-grade dwelling units.

Mechanically, the work starts with a detailed site assessment, where our team evaluate setbacks, zoning, utility access, and structural feasibility. From there, blueprints 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, HVAC, drywall, flooring, and exterior finishes. The result is a fully functional living unit adjacent to or detached from your main home.

The difference between a good and a great ADU build is the level of craftsmanship at every stage. Materials must be selected to complement the existing structure. Systems like HVAC and drainage must be sized for independent daily use. Brother & Brother Builders handles every ADU construction job 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 increasing appraised value substantially when it's time to sell.
• Revenue Generation — A completed ADU can be rented as a long-term rental or short-term vacation unit, generating steady monthly revenue for the homeowner.
• Housing for Extended Family — ADU construction offers family members a comfortable home of their own without leaving the property.
• Personalized Layouts — From modern studio layouts, ADU construction is adaptable to the intended occupant's lifestyle.
• Faster Permitting in California — Recent state legislation has minimized the permitting obstacles associated with ADU construction, resulting in a timeline that is faster and more cost-efficient than ever before.
• Efficient Use of Your Lot — 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 creates a truly separate unit where residents have their own space.
• Durable Return on Investment — A well-built ADU holds its value for decades, providing both functional space and financial upside.

The ADU Construction Journey Step by Step

1. Initial Property Assessment and Feasibility Review — Our builders assess your property to evaluate setbacks, lot coverage limits, and utility connections. This phase answers exactly what's possible before any money is spent on design.
2. Architectural Drafting and Space Planning — Experienced draftspeople create precise architectural drawings tailored to your needs. Space is thoughtfully allocated to maximize function and livability.
3. Permit Submission and Municipal Review — ADU construction in San Jose requires submitting plans to the city's building department for review and approval. Brother & Brother Builders coordinates the permitting on your behalf, resolving any revision requests promptly.
4. Excavation and Foundation Installation — Once permits are issued, on-site work kicks off. This covers land preparation, pouring the concrete foundation, and running initial plumbing and electrical conduits.
5. Shell Construction and Exterior Finishing — Framing is completed followed by roofing, siding, windows, and exterior doors. During this step, the ADU becomes recognizable as a structure.
6. Mechanical, Electrical, and Plumbing Installation — Skilled tradespeople 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.
7. Finishes, Fixtures, and Final Walkthrough — Countertops, hardware, finishes, and fixtures are fitted and completed to your specifications. A final city inspection issues the certificate of occupancy 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 generally fit within a few recognizable groups. If you own a single-family home 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 common ADU construction clients, along with families accommodating adult children who need housing.

You may also be someone who needs a dedicated professional workspace and wants a separate office or studio space that is distinct from your family's daily life. Landlords and real estate investors who already own residential properties are also well suited for ADU construction, since the return on investment is well-documented.

Homeowners who may want to pause and evaluate include lots that are below minimum size thresholds. Sites with underground infrastructure conflicts may face additional constraints. Brother & Brother Builders reviews each property on its own merits to advise you on what's feasible.

ADU Construction Common Questions Answered

How long does ADU construction generally take from start to finish?

The complete duration for ADU construction typically ranges from 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 starting early is important. Smaller detached units can move faster, while multi-room detached cottages take longer to complete.

What does ADU construction cost in San Jose?

Costs vary widely based on project complexity and finishes selected. Locally, ADU construction generally falls between $150,000 to $400,000 or more for a detached new build. Interior conversion projects tend to cost less, sometimes between $75,000 and $140,000. A precise cost projection 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 where the ADU is being built. Standalone ADU projects are typically less disruptive, since the construction zone is separate. Garage conversions or attached additions may require temporary access during specific stages like framing or MEP rough-in. We provide advance notice about any phases that may affect your routine.

Do I need to vacate the property during ADU construction?

Generally speaking, you won't have to vacate your primary residence during ADU construction. The vast majority of projects are set up to let you continue living in the home throughout the construction timeline. There are edge cases if major utility upgrades affect the main house in ways that briefly affect habitability. The team at Brother & Brother Builders will walk you through any potential disruptions during the kickoff meeting.

How long will an ADU built through professional ADU construction remain in good condition?

A well-built ADU can be expected to last as long as your primary home — 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 high-quality components and comply with all local building codes to deliver a structure that stands the test of time.

ADU Construction for Local Homeowners

The communities throughout San Jose provide a wide range of property types that are well suited for ADU construction. Property owners near the Almaden Valley area often discover their properties work well for both attached and detached projects. Neighborhoods near Blossom Hill Road are increasingly popular for ADU construction as housing demand rises. If you're located closer to Evergreen, our team knows the permitting landscape well.

The City of San Jose's building department has developed specific protocols 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 these local conditions means smoother project delivery from design through the final walkthrough.

Schedule Your ADU Construction Assessment Today

When you want to move forward with ADU construction, Brother & Brother Builders is ready to guide you. We bring proven skills 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 share clear expectations of what the project will involve.

Reach out to our team to begin the conversation. Whether you're in the early stages of planning, our team is happy to discuss timelines, costs, and design possibilities and make sure you feel confident before committing. 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