Expand Your Home with Professional ADU Construction
Homeowners across San Jose, CA are finding that adding an accessory dwelling unit is one of the most practical investments they can make. ADU construction opens the door to a powerful new living space on your existing property — whether you want to create a private workspace. Brother & Brother Builders has helped hundreds of local homeowners see these visions to life with craftsmanship and transparency.
The demand for ADU construction has surged 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 increase density responsibly. Whether you're building a detached backyard cottage, a garage conversion, or an attached addition, ADU construction offers greater control over how your property serves your household.
At Brother & Brother Builders, we draw on extensive hands-on experience to every ADU construction job. Our team is familiar with city and county requirements, the engineering considerations, and the planning steps that make an ADU functional. Should you want to learn about what ADU construction could mean for 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 self-contained living space — equipped with a kitchen, bathroom, sleeping area, and its own entryway — that is located on the same parcel as a primary residence. ADU construction can take several forms, including detached backyard units, attached additions, garage conversions, and even basement or interior conversions.
Mechanically, the process begins with a comprehensive review of your lot, where our professionals evaluate property boundaries, available square footage, and infrastructure capacity. From there, blueprints are prepared and submitted to the relevant municipal authority. Once approvals are in place, ADU construction moves into the physical build phase — which encompasses site preparation, framing, mechanical systems, weatherproofing, read more and interior finishing. The result is a move-in-ready living unit adjacent to or detached from your main home.
What sets quality ADU construction apart is the attention to detail at every stage. Components should be specified to match the primary home's aesthetic. Systems like plumbing and electrical must be built for long-term residential demand. Brother & Brother Builders approaches every build with the same technical discipline we bring to full custom home projects.
Key Advantages ADU Construction
- Increased Property Value — ADU construction contributes significant market value to your property, often returning more than the build cost when it's time to sell.
- Revenue Generation — A completed ADU may be listed as a long-term rental or short-term vacation unit, creating ongoing passive income for the homeowner.
- Multi-Generational Living — ADU construction offers family members a comfortable home of their own without leaving the property.
- Personalized Layouts — From open-plan one-bedrooms, ADU construction is adaptable to your household's priorities.
- Faster Permitting in California — Recent state legislation has minimized the red tape associated with ADU construction, making the process that is faster and less expensive than ever before.
- Responsible Property Development — Building an ADU works within your current footprint instead of consuming open land, which aligns with sustainability goals.
- Separate Entrances and Spaces — Unlike a bedroom addition, ADU construction produces a fully self-contained unit where tenants live autonomously.
- Long-Term Investment Security — A well-built ADU remains an asset 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 experts review your property to determine what type of ADU is allowed and where it can be placed. This step tells you exactly what's possible before any time is invested in drawings.
- Custom Design and Architectural Planning — Our design team create precise architectural drawings based on your goals. Layouts are carefully considered to maximize function and livability.
- Permitting and City Approval — 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.
- Excavation and Foundation Installation — Once permits are granted, on-site work kicks off. This includes grading the site, completing foundation work, and setting up utilities.
- Framing, Roofing, and Exterior Work — The structural frame is erected followed by roofing, siding, windows, and exterior doors. This phase, the ADU takes its visible shape.
- Interior Systems and Infrastructure — Licensed subcontractors install the plumbing lines, electrical wiring, and HVAC systems that make the ADU fully functional. Every system is reviewed at designated stages throughout ADU construction.
- Interior Completion and City Sign-Off — Countertops, hardware, finishes, and fixtures are installed and finished to the agreed design. A final city inspection confirms the unit is code-compliant and the unit is officially approved for use.
Who Is a Right Fit for ADU Construction?
Homeowners who benefit most from ADU construction typically fall into a few clear categories. If you own a single-family home with a backyard, garage, or basement that could be converted, 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 navigating multigenerational living situations.
ADU construction also suits someone who runs a small business and wants a private work environment that remains away from your family's daily life. Real estate-minded homeowners who are building a portfolio 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. Parcels in historic districts or HOA-restricted communities may require additional review. Our team can assess each property case by case to provide realistic options.
ADU Construction Common Questions Answered
How long does ADU construction generally take from start to finish?
The complete duration for ADU construction usually runs between six to fourteen months, depending on design complexity and local permitting timelines. City review on its own can take two to four months in San Jose, so planning ahead matters. Simpler garage conversions may complete more quickly, while multi-room detached cottages fall toward the upper end of the timeline.
What does ADU construction usually run in terms of budget?
Costs vary widely based on project complexity and finishes selected. Locally, 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. A precise cost projection can only be produced following a full site assessment.
Is ADU construction disruptive while it's underway?
The level of disruption depends on whether you're converting existing space or building new. Detached backyard builds are typically less disruptive, since work happens away from the main house. Projects that connect to the main structure may involve some shared wall work 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 move out during ADU construction?
For the majority of homeowners, you won't have to vacate your primary residence during ADU construction. Most builds are structured to allow you stay in your primary unit throughout the process. Exceptions may arise if interior conversion work touches shared systems in ways that require short-term access disruption. Our project managers 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 the main residence — typically 50 years or more. Durability depends to the standard of construction, how well routine maintenance is performed, and how proactively issues are resolved over time. Brother & Brother Builders specifies commercial-grade materials and comply with all local building codes to ensure lasting performance.
ADU Construction for San Jose 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 frequently see their parcels accommodate detached backyard units nicely. The Berryessa area are seeing more homeowners add secondary units as families expand. From neighborhoods near the Guadalupe River Park corridor to those near Branham Lane, our team knows the permitting landscape well.
San Jose's permitting office follows defined procedures for ADU construction that our team navigates routinely. Location near major arterials like Story Road or Tully Road can influence utility connection requirements for a given ADU project. Our familiarity with the San Jose permitting environment means smoother project delivery from the first meeting to the final inspection.
Schedule 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. Our builders provide proven skills in ADU construction across a wide range of project types — from modest studio builds to large custom detached cottages. The process begins with a comprehensive site assessment where we understand your vision and provide an honest assessment of what the project will involve.
Get in touch with our office to begin the conversation. Even if you're just exploring the idea, we enjoy answer questions, share examples of our work and help you take the next step. Building an ADU is a major decision — and our goal is to ensure it delivers real value.
Brother & Brother Builders | 3109 Stevens Creek Boulevard | San Jose CA 95117 | (888) 412-2632