Expand Your Home with Professional ADU Construction
Families in San Jose, CA are discovering 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 helped hundreds of local homeowners bring these projects to life with precision and transparency.
The demand for ADU construction has surged in recent years, and it's easy to understand why. California state law has simplified the process for homeowners to add these secondary units, and local municipalities like San Jose have supported the trend as a way to address housing needs. 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 apply deep hands-on experience to every ADU construction project. Our team is familiar with city and county requirements, the engineering considerations, 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 will walk you through everything you need to know.
What Is ADU Construction?
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 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 below-grade dwelling units.
Mechanically, the process begins with a detailed site assessment, where our builders evaluate lot dimensions, existing structures, soil conditions, and local code requirements. From there, design plans are prepared and submitted to the city for permit approval. Once the paperwork is cleared, ADU construction enters the physical build phase — which includes foundation work, framing, roofing, plumbing, electrical, insulation. The result is a move-in-ready living unit connected to or independent of your main home.
What sets quality ADU construction apart is the level of craftsmanship at every stage. Materials must be selected to match the primary home's aesthetic. Systems like wiring and water supply must be built for long-term residential demand. Brother & Brother Builders approaches every build with the same technical discipline we use on major custom home projects.
Key Benefits ADU Construction
- Boosted Home Equity — ADU construction contributes significant market value to your property, often increasing appraised value substantially when it's time to sell.
- Revenue Generation — A completed ADU is leasable as a long-term rental or short-term vacation unit, creating ongoing passive income for the homeowner.
- Multi-Generational Living — ADU construction provides adult children a self-contained residence without moving to another neighborhood.
- Customization Options — From modern studio layouts, ADU construction can be tailored to your specific needs.
- Streamlined Approval Process — Recent state legislation has minimized the permitting obstacles associated with ADU construction, making the process that is faster and less expensive than ever before.
- Sustainable Land Use — Building an ADU maximizes the land you already own instead of consuming open land, which contributes to sustainability goals.
- Separate Entrances and Spaces — Unlike a bedroom addition, ADU construction delivers a genuinely independent unit where occupants have full privacy.
- Durable Return on Investment — A well-built ADU remains an asset for the long haul by offering both functional space and financial upside.
The ADU Construction Process Step by Step
- Site Evaluation and Zoning Analysis — Our team visits your property to evaluate setbacks, lot coverage limits, and utility connections. This stage clarifies exactly what's possible before any time is invested in drawings.
- Custom Design and Architectural Planning — Our design team create comprehensive blueprints reflecting your priorities. Space is thoughtfully allocated to maximize function and livability.
- Filing for Building Permits — ADU construction in San Jose involves filing drawings to the city's building department for sign-off and verification. We manage this entire process on your behalf, responding to review feedback promptly.
- Excavation and Foundation Installation — Once permits are approved, physical construction begins. This covers land preparation, completing foundation work, and setting up utilities.
- Framing, Roofing, and Exterior Work — Framing is completed followed by roofing, siding, windows, and exterior doors. This phase, the ADU transforms from a concept to a building.
- MEP Systems Rough-In — Skilled tradespeople install the heating, cooling, drainage, and power infrastructure that make the ADU fully functional. All work is inspected at required milestones throughout ADU construction.
- Interior Completion and City Sign-Off — Trim, appliances, tile, and lighting are installed and finished to the agreed design. A final city inspection issues the certificate of occupancy and the ADU is ready for use.
Who Is a Strong Candidate for ADU Construction?
Homeowners who benefit most from ADU construction often belong to a few recognizable groups. If you own a single-family home with enough lot space to meet setback requirements, you're already in a good starting place. Homeowners looking to generate income through rental are among the most common ADU construction clients, along with families supporting elderly parents.
Another strong candidate is someone who works from home 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 a natural fit 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. Sites with underground infrastructure conflicts may face additional constraints. Brother & Brother Builders reviews each property individually and honestly to recommend the right path forward.
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, influenced by the type of unit being built and how quickly approvals come through. Permitting alone can take several months in San Jose, so starting early is important. Smaller detached units may complete more quickly, while larger new construction ADUs require more time.
What does ADU construction typically cost?
Costs vary widely based on whether it's a conversion or new construction. For most projects in this region, ADU construction generally falls between $150,000 to $400,000 or more for a standalone backyard unit. Attached ADU additions are generally priced lower, sometimes starting around $80,000 depending on scope. A detailed estimate can only be given after completing a thorough property review.
Is ADU construction disruptive while it's underway?
The day-to-day impact depends on where the ADU is being built. Standalone ADU projects are typically less disruptive, since the construction zone is separate. Interior conversions may involve some shared wall work during certain phases of construction. Our team communicates clearly about what to expect at each stage.
Do I need to vacate the property during ADU construction?
For the majority of homeowners, you do not need to vacate your house during ADU construction. Most builds are set up to let you remain on the property throughout the process. There are edge cases if interior conversion work touches shared systems in ways that temporarily impact livability. The team at Brother & Brother Builders will walk you through any potential disruptions during the pre-construction consultation.
How long will an ADU built through professional ADU construction hold up?
Any ADU built to code with professional oversight is designed to last as long as the main residence — typically 50 years or more. How long it lasts comes down to the quality of materials used, how well routine maintenance is performed, and whether systems like roofing and plumbing are serviced more info regularly. Brother & Brother Builders specifies commercial-grade materials and build to current California residential standards to ensure lasting performance.
ADU Construction for Local Homeowners
The communities throughout San Jose provide a diverse mix of property types that are ideally positioned for ADU construction. Residents in the Rose Garden district often discover their properties accommodate detached backyard units nicely. Neighborhoods near Blossom Hill Road have seen growing ADU activity as families expand. If you're located closer to Evergreen, our team has project experience in the area.
The City of San Jose's building department applies particular standards for ADU construction that our team navigates routinely. Proximity to transit corridors can influence utility connection requirements for a given ADU project. Our team's knowledge of this region's building landscape means smoother project delivery from kickoff through certificate of occupancy.
Start Your ADU Construction Assessment Today
When you want to explore what an ADU could look like on your lot, Brother & Brother Builders is the team to call. Our builders provide proven skills in ADU construction including all types of project types — from simple garage conversions to large custom detached cottages. Our approach opens with a comprehensive site assessment 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.
Reach out to our team to schedule a site visit. No matter where you are in the decision-making process, we enjoy walk through your options, review completed projects and help you take the next step. ADU construction is a significant investment — and we're committed to helping you get it right.
Brother & Brother Builders | 3109 Stevens Creek Boulevard | San Jose CA 95117 | (888) 412-2632