Brother & Brother Builders

Unlock New Space with Expert ADU Construction

Homeowners across San Jose, CA are finding that adding an accessory dwelling unit is one of the smartest investments they can make. ADU construction opens the door to 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 turn these plans to life with precision and integrity.

The demand for ADU construction has surged in recent years, and it's no mystery. California state law has streamlined permitting for homeowners to construct these secondary units, and local municipalities like San Jose have supported 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 offers greater control over how your property works.

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 details, and the planning steps that make an ADU beautiful. If you've been thinking about what ADU construction could mean for your property, this guide explains everything you need to know.

What Is an ADU Build?

ADU construction describes 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 — equipped with a kitchen, bathroom, sleeping area, and its own access point — that exists on the same lot as a primary residence. ADU construction comes in multiple configurations, including detached backyard units, attached additions, garage conversions, and even interior space reconfigurations.

Mechanically, the work starts with a thorough property evaluation, where our builders evaluate lot dimensions, existing structures, soil conditions, and local code requirements. From there, design plans are prepared and submitted to the relevant municipal authority. Once permits are secured, ADU construction moves into the physical build phase — which encompasses site preparation, framing, mechanical systems, weatherproofing, and interior finishing. The result is a move-in-ready living unit attached to or separate from your main home.

What separates excellent ADU construction from an average project is the depth of planning at every stage. Components should be specified to match the primary home's aesthetic. Systems like HVAC and drainage must be designed to handle full-time occupancy. Brother & Brother Builders treats each project with the same high standards we use on major custom home projects.

Key Advantages ADU Construction

• Boosted Home Equity — ADU construction contributes significant market value to your property, often generating strong equity gains 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, generating steady monthly revenue for the homeowner.
• Space for Loved Ones — ADU construction gives aging parents a comfortable home of their own without leaving the property.
• Design Flexibility — From two-bedroom configurations, ADU construction may be customized to the intended occupant's lifestyle.
• Faster Permitting in California — Recent state legislation has cut down the red tape 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 works within your current footprint instead of requiring new development, which supports broader sustainability goals.
• Privacy for All Residents — Unlike a bedroom addition, ADU construction produces a fully self-contained unit where residents have their own space.
• Lasting Financial Benefit — A well-built ADU continues to produce returns for decades, providing both usable housing and equity growth.

The ADU Construction Procedure Step by Step

1. Initial Property Assessment and Feasibility Review — Our experts review your property to analyze zoning rules, slope conditions, and available square footage. This step tells you exactly what can be built before any money is spent on design.
2. Architectural Drafting and Space Planning — Experienced draftspeople create detailed floor plans based on your goals. Layouts are carefully considered to optimize daily use.
3. Permit Submission and Municipal Review — ADU construction in San Jose requires submitting plans to the city's building department for inspection and clearance. Our team handles all submissions on your behalf, resolving any revision requests promptly.
4. Excavation and Foundation Installation — Once permits are approved, the build starts. This includes grading the site, pouring the concrete foundation, and establishing utility connections.
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 — Certified technicians install the heating, cooling, drainage, and power infrastructure that make the ADU operationally complete. Inspections are completed at designated stages throughout ADU construction.
7. Interior Completion and City Sign-Off — Flooring, cabinetry, fixtures, paint are placed and inspected to the agreed design. A final city inspection confirms the unit is code-compliant 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 recognizable groups. If you are a homeowner with available square footage under zoning rules, you're already well-positioned. Homeowners looking to generate income through rental are among the most financially driven ADU construction clients, along with families accommodating adult children who need housing.

ADU construction also suits someone who works from home and wants a separate office or studio space that doesn't interfere with your family's daily life. Property investors and rental owners who are building a portfolio are also well suited for ADU construction, since the return on investment is well-documented.

Those who should discuss alternatives first include properties with significant setback limitations. Sites with underground infrastructure conflicts may require additional review. Our experts will evaluate each property on its own merits to recommend the right path forward.

ADU Construction Frequently Asked Questions

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

The full timeline for ADU construction typically ranges from six to fourteen months, depending on design complexity and city review schedules. The approval phase alone can take a significant portion of the overall timeline in San Jose, so starting early is important. Straightforward interior conversions can move faster, while multi-room detached cottages require more time.

What does ADU construction typically cost?

Pricing depends on many factors based on project complexity and finishes selected. Locally, ADU construction generally falls between $150,000 to $400,000 or more for a fully custom construction. Interior conversion projects are generally priced lower, sometimes between $75,000 and $140,000. A precise cost projection can only be given after completing a formal feasibility evaluation.

Is ADU construction disruptive while it's underway?

The day-to-day impact depends on the project's location on your property. Detached backyard builds are generally the least intrusive, since the construction zone is separate. 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 vacate the property during ADU construction?

For the majority of homeowners, you won't have to vacate your primary residence during ADU construction. Most builds are designed so that you stay in your primary unit throughout the build. There are edge cases if major utility upgrades affect the main house in ways that temporarily impact livability. The team at Brother & Brother Builders will flag these situations during the kickoff meeting.

How long will an ADU built through professional ADU construction hold up?

A well-built ADU is designed to last as long as any standard residential structure — typically 50 years or more. Durability depends to the quality of materials used, how consistently minor repairs are addressed, and if mechanical components are maintained on schedule. Brother & Brother Builders specifies commercial-grade materials and build to current California residential standards to ensure lasting performance.

ADU Construction for San Jose Homeowners

The communities throughout San Jose provide a diverse mix of property types that are perfectly suited for ADU construction. Property owners near the Almaden Valley area often discover their properties accommodate detached backyard units nicely. Communities around the Capitol Expressway corridor have seen growing ADU activity as housing demand rises. From neighborhoods near the Guadalupe River Park corridor to those near Branham Lane, our team knows the permitting landscape well.

Local regulatory bodies in this area applies particular standards for ADU construction that our team navigates routinely. Access to infrastructure along thoroughfares like Monterey Road can impact the design approach for a given ADU project. Our familiarity with this region's building landscape means fewer surprises from the first meeting to the final inspection.

Schedule Your ADU Construction Planning Session Today

Should you be thinking about how to add an ADU to your property, Brother & Brother Builders is the team to call. Our builders provide years of hands-on experience in ADU construction across a wide range of project types — from simple garage conversions to fully independent secondary homes. Our approach opens with a detailed, no-pressure consultation 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're glad to answer questions, share examples of our work and give here you the clarity you need to move forward. ADU construction is a significant investment — 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