Unlock New Space with Quality ADU Construction
Families in San Jose, CA are finding that adding an accessory dwelling unit is one of the most rewarding investments they can make. ADU construction creates a flexible new living space on your existing property — whether you want to create a private workspace. Brother & Brother Builders has helped hundreds of local homeowners turn these plans to life with precision and transparency.
The interest in ADU construction has grown rapidly in recent years, and it's no mystery. California state law has simplified the process for homeowners to construct 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 provides increased control over how your property serves your household.
At Brother & Brother Builders, we draw on extensive hands-on experience to every ADU construction project. Our team understands the local permitting process, the engineering requirements, and the planning steps that make an ADU beautiful. Should you want to learn about what ADU construction could mean for your property, this guide explains everything you need to know.
What Is an ADU Build?
ADU construction involves 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 sits on the same property as a primary residence. ADU construction includes various structural types, including detached backyard units, attached additions, garage conversions, and even interior space reconfigurations.
Mechanically, everything kicks off with a detailed site assessment, where our builders evaluate property boundaries, available square footage, and infrastructure capacity. From there, architectural drawings 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, HVAC, drywall, flooring, and exterior finishes. The result is a completely finished living unit connected to or independent of 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 match the primary home's aesthetic. Systems like plumbing and electrical must be designed to handle full-time occupancy. Brother & Brother Builders approaches every build with the same technical discipline we apply to large-scale custom home projects.
Key Advantages ADU Construction
- Increased Property Value — ADU construction contributes significant market value to your property, often generating strong equity gains when it's time to sell.
- Rental Income Potential — A completed ADU is leasable as a long-term rental or short-term vacation unit, creating ongoing passive income for the homeowner.
- Space for Loved Ones — ADU construction offers family members a self-contained residence without leaving the property.
- Design Flexibility — From modern studio layouts, ADU construction is adaptable to your specific needs.
- Faster Permitting in California — Recent state legislation has cut down the red tape associated with ADU construction, making the process that is faster and less expensive than ever before.
- Sustainable Land Use — Building an ADU works within your current footprint instead of requiring new development, which contributes to sustainability goals.
- Separate Entrances and Spaces — Unlike a bedroom addition, ADU construction creates a truly separate unit where tenants live autonomously.
- 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 Journey Step by Step
- Site Evaluation and Zoning Analysis — Our experts review your property to determine what type of ADU is allowed and where it can be placed. This phase answers exactly what can be built before any money is spent on design.
- Custom Design and Architectural Planning — Our design team create precise architectural drawings tailored to your needs. Every square foot is planned to optimize daily use.
- Filing for Building Permits — ADU construction in San Jose involves filing drawings to the city's building department for review and approval. We manage this entire process on your behalf, responding to review feedback promptly.
- Excavation and Foundation Installation — Once permits are granted, physical construction begins. This covers land preparation, laying the structural base, and establishing utility connections.
- Structural Framing and Weatherproofing — Walls and roof systems go up followed by roofing, siding, windows, and exterior doors. During this step, the ADU becomes recognizable as a structure.
- Mechanical, Electrical, and Plumbing Installation — Certified technicians install the water supply, drain lines, and electrical panel that make the ADU fully functional. Every system is reviewed at each code checkpoint throughout ADU construction.
- Interior Finishing and Final Inspections — Flooring, cabinetry, fixtures, paint are fitted and completed to the agreed design. A final city inspection issues the certificate of occupancy and your new space is cleared for use.
Who Is a Right Fit for ADU Construction?
People who see the greatest return from ADU construction often belong to a few clear categories. If you have a residential property with a backyard, garage, or basement that could be converted, you're already a strong candidate. Homeowners wanting to add a revenue stream 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 separate office or studio space that remains away from your family's daily life. Landlords and real estate investors who already own residential properties are also a natural fit for ADU construction, since the return on investment is well-documented.
Situations where ADU construction may not be the best first step include sites with unusual utility access challenges. Sites with underground infrastructure conflicts may face additional constraints. Our experts will evaluate each property on its own merits to provide realistic options.
ADU Construction Common Questions Answered
How long does ADU construction generally take from start to finish?
The total process 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. Simpler garage conversions often finish in the lower end of the range, while multi-room detached cottages require more time.
What does ADU construction cost in San Jose?
Costs vary widely based on project complexity and finishes selected. For most check here projects in this region, ADU construction commonly costs $150,000 to $400,000 or more for a standalone backyard unit. Interior conversion projects often come in under, sometimes in the $80,000 to $150,000 range. An accurate budget can only be given after completing a full site assessment.
Is ADU construction intrusive while it's underway?
The level of disruption depends on the project's location on your property. Standalone ADU projects are typically less disruptive, since the construction zone is separate. Garage conversions or attached additions may create short-term inconveniences during certain phases of construction. Brother & Brother Builders keeps you informed about upcoming work and timelines.
Do I need to leave my home during ADU construction?
For the majority of homeowners, you are not required to vacate your primary residence during ADU construction. Most job sites are structured to allow you stay in your primary unit throughout the process. Exceptions may arise if major utility upgrades affect the main house in ways that require short-term access disruption. The team at Brother & Brother Builders will discuss these scenarios during the planning phase.
How long will an ADU built through professional ADU construction last?
An ADU constructed with quality materials is designed to last as long as the main residence — typically 50 years or more. Longevity is tied to the standard of construction, how well routine maintenance is performed, and whether systems like roofing and plumbing are serviced regularly. 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 San Jose Homeowners
The communities throughout San Jose provide a diverse mix of property types that are well suited for ADU construction. Homeowners in the Willow Glen neighborhood have found their lots work well for both attached and detached projects. The Berryessa area are increasingly popular for ADU construction as multigenerational living becomes more common. If you're located closer to Evergreen, our team knows the permitting landscape well.
Local regulatory bodies in this area follows defined procedures for ADU construction that require a builder familiar with local expectations. Access to infrastructure along thoroughfares like Monterey Road can influence utility connection requirements for a given ADU project. Our familiarity with these local conditions means smoother project delivery from the first meeting to the final inspection.
Book Your ADU Construction Planning Session 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 for many different project types — from modest studio builds to fully independent secondary homes. Every project starts with a thorough and honest property review where we learn what you're trying to accomplish and share clear expectations of what's achievable.
Reach out to our team to begin the conversation. Even if you're just exploring the idea, our team is happy to discuss timelines, costs, and design possibilities and help you take the next step. This type of project is a meaningful commitment — and we're committed to helping you get it right.
Brother & Brother Builders | 3109 Stevens Creek Boulevard | San Jose CA 95117 | (888) 412-2632