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 powerful new living space on your existing property — whether you want to generate rental income. Brother & Brother Builders has supported hundreds of local homeowners see these visions to life with skill and integrity.
The interest in ADU construction has increased significantly in recent years, and it's not hard to see why. California state law has streamlined permitting for homeowners to add these secondary units, and local municipalities like San Jose have supported 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 offers greater control over how your property functions.
At Brother & Brother Builders, we apply deep 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 beautiful. Should you want to learn about what ADU construction could look like on your property, this guide covers 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 complete living space — including a kitchen, bathroom, sleeping area, and its own entryway click here — that exists on the same lot as a primary residence. ADU construction includes various structural types, including detached backyard units, attached additions, garage conversions, and even below-grade dwelling units.
Mechanically, everything kicks off with a comprehensive review of your lot, where our builders evaluate setbacks, zoning, utility access, and structural feasibility. From there, architectural drawings are prepared and submitted to the local building department. Once approvals are in place, ADU construction moves into 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 connected to or independent of your main home.
What sets quality ADU construction apart is the level of craftsmanship at every stage. Products need to be chosen to match the primary home's aesthetic. Systems like wiring and water supply must be built for long-term residential demand. Brother & Brother Builders handles every ADU construction job with the same technical discipline we use on major 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 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 provides adult children a private, independent living space without leaving the property.
- Personalized Layouts — From modern studio layouts, ADU construction can be tailored to the intended occupant's lifestyle.
- Simplified Regulatory Path — Recent state legislation has minimized the red tape associated with ADU construction, resulting in a timeline that is faster and more affordable than ever before.
- Responsible Property Development — Building an ADU uses your existing lot instead of requiring new development, which supports broader sustainability goals.
- Privacy for All Residents — Unlike a bedroom addition, ADU construction creates a truly separate unit where tenants live autonomously.
- Lasting Financial Benefit — A well-built ADU continues to produce returns for many years and generates both functional space and financial upside.
The ADU Construction Process Step by Step
- Initial Property Assessment and Feasibility Review — Our builders assess your property to analyze zoning rules, slope conditions, and available square footage. This step tells you exactly what can be built before any resources go toward planning.
- Blueprint Development and Layout Design — Experienced draftspeople create comprehensive blueprints based on your goals. Every square foot is planned to maximize function and livability.
- Permit Submission and Municipal Review — ADU construction in San Jose requires submitting plans to the city's building department for sign-off and verification. Brother & Brother Builders coordinates the permitting on your behalf, responding to review feedback promptly.
- Ground Prep and Structural Base — Once permits are issued, on-site work kicks off. This involves leveling and prepping the ground, pouring the concrete foundation, and establishing utility connections.
- Structural Framing and Weatherproofing — Framing is completed followed by weatherproofing and exterior finish materials. This phase, the ADU transforms from a concept to a building.
- MEP Systems Rough-In — Skilled tradespeople install the plumbing lines, electrical wiring, and HVAC systems that make the ADU ready for occupancy. All work is inspected at required milestones throughout ADU construction.
- Interior Completion and City Sign-Off — Trim, appliances, tile, and lighting are placed and inspected to the agreed design. A final city inspection confirms the unit is code-compliant and your new space is cleared for use.
Who Is a Strong Candidate for ADU Construction?
People who see the greatest return from ADU construction generally fit within a few recognizable groups. If you have a residential property with enough lot space to meet setback requirements, you're already well-positioned. Homeowners hoping to offset mortgage costs through rental are among the most common ADU construction clients, along with families navigating multigenerational living situations.
You may also be someone who runs a small business and wants a detached creative or business space that doesn't interfere with your family's daily life. Real estate-minded homeowners who already own residential properties are also prime candidates for ADU construction, since the long-term value is proven.
Situations where ADU construction may not be the best first step include properties with significant setback limitations. Sites with underground infrastructure conflicts may require additional review. Brother & Brother Builders reviews each property individually and honestly to provide realistic options.
ADU Construction FAQ
How long does ADU construction generally take from start to finish?
The full timeline for ADU construction usually runs between six to fourteen months, depending on design complexity and local permitting timelines. Permitting 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 fall toward the upper end of the timeline.
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 standalone backyard unit. Attached ADU additions 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 difficult to live through while it's underway?
How much the build affects daily life depends on where the ADU is being built. Detached backyard builds are typically less disruptive, since the crew operates at a distance from your living areas. Interior conversions may create short-term inconveniences during certain phases of construction. Our team communicates clearly about upcoming work and timelines.
Do I need to move out during ADU construction?
Generally speaking, you are not required to vacate your main home during ADU construction. The vast majority of projects are designed so that 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 require short-term access disruption. Our project managers will flag these situations 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 the main residence — often several decades with routine maintenance. Durability depends to the quality of materials used, how consistently minor repairs are addressed, and whether systems like roofing and plumbing are serviced regularly. Brother & Brother Builders specifies commercial-grade materials and build to current California residential standards to deliver a structure that stands the test of time.
ADU Construction for Local Homeowners
The communities throughout San Jose provide a diverse mix of property types that are ideally positioned for ADU construction. Homeowners in the Willow Glen neighborhood frequently see their parcels accommodate detached backyard units nicely. Communities around the Capitol Expressway corridor have seen growing ADU activity as housing demand rises. Whether your property is near downtown San Jose, our team has project experience in the area.
San Jose's permitting office follows defined procedures for ADU construction that our team navigates routinely. Proximity to transit corridors can influence utility connection requirements for a given ADU project. Our familiarity with the San Jose permitting environment means fewer surprises from kickoff through certificate of occupancy.
Start Your ADU Construction Planning Session Today
Should you be thinking about how to explore what an ADU could look like on your lot, Brother & Brother Builders is the team to call. We bring licensed expertise in ADU construction for many different project types — from small attached additions 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.
Get in touch with our office to set up your consultation. No matter where you are in the decision-making process, we enjoy discuss timelines, costs, and design possibilities and make sure you feel confident before committing. 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