Unlock New Space with Quality 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 flexible new living space on your existing property — whether you want to create a private workspace. Brother & Brother Builders has guided hundreds of local homeowners see these visions to life with skill and transparency.
The interest in ADU construction has grown rapidly in recent years, and it's not hard to see why. California state law now makes it easier 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 want to build 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 build. Our team is familiar with city and county requirements, the engineering considerations, and the design choices that make an ADU beautiful. If you've been thinking about what ADU construction could mean for your property, this guide will walk you through everything you need to know.
What Is an ADU Build?
ADU construction refers to the process of engineering, filing for, and completing an accessory dwelling unit on a residential property. An accessory dwelling unit is a fully independent living space — equipped with a kitchen, bathroom, sleeping area, and its own entryway — 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, the process begins with a detailed site assessment, where our builders evaluate lot dimensions, existing structures, soil conditions, and local code requirements. From there, blueprints are prepared and submitted to the relevant municipal authority. Once the paperwork is cleared, ADU construction transitions to the physical build phase — which includes foundation work, framing, roofing, plumbing, electrical, insulation. The result is a completely finished living unit adjacent to or detached from your main home.
What sets quality ADU construction apart is the attention to detail at every stage. Materials must be selected to align with the neighborhood's character. Systems like plumbing and electrical must be sized for independent daily use. Brother & Brother Builders treats each project with the same professional rigor we bring to full custom home projects.
Key Benefits ADU Construction
- Higher Resale Potential — 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 provides adult children a comfortable home of their own without leaving the property.
- Personalized Layouts — From open-plan one-bedrooms, ADU construction may be customized to your household's priorities.
- Streamlined Approval Process — Recent state legislation has reduced the barriers and delays associated with ADU construction, creating a path that is faster and more affordable than ever before.
- Responsible Property Development — Building an ADU maximizes the land you already own instead of requiring new development, which aligns with sustainability goals.
- Privacy for All Residents — Unlike a bedroom addition, ADU construction produces a fully self-contained unit where occupants have full privacy.
- Long-Term Investment Security — A well-built ADU holds its value for decades, providing both usable housing and equity growth.
The ADU Construction Journey Step by Step
- Initial Property Assessment and Feasibility Review — Our builders assess 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 resources go toward planning.
- Architectural Drafting and Space Planning — Our design team create comprehensive blueprints reflecting your priorities. Space is thoughtfully allocated to create practical, comfortable living.
- Filing for Building Permits — ADU construction in San Jose involves filing drawings to the city's building department for sign-off and verification. Brother & Brother Builders coordinates the permitting on your behalf, addressing any city comments promptly.
- Excavation and Foundation Installation — Once permits are issued, the build starts. This covers land preparation, laying the structural base, and running initial plumbing and electrical conduits.
- Shell Construction and Exterior Finishing — Walls and roof systems go up followed by insulation, sheathing, and exterior cladding. During this step, the ADU takes its visible shape.
- MEP Systems Rough-In — Skilled tradespeople install the plumbing lines, electrical wiring, and HVAC systems that make the ADU fully functional. All work is inspected at required milestones throughout ADU construction.
- Finishes, Fixtures, and Final Walkthrough — Trim, appliances, tile, and lighting are fitted and completed to the approved plan. A final city inspection grants legal occupancy status and the ADU is ready for use.
Who Is a Good Candidate for ADU Construction?
Homeowners who benefit most from ADU construction generally fit within a few recognizable groups. If you have a residential property with available square footage under zoning rules, you're already in a good starting place. Homeowners wanting to add a revenue stream through rental are among the most motivated ADU construction clients, along with families accommodating adult children who need housing.
ADU construction also suits someone who works from home and wants a private work environment that doesn't interfere with your family's daily life. Property investors and rental owners who want to maximize their land are also prime candidates for ADU construction, since rental income frequently offsets build costs.
Those who should discuss alternatives first include lots that are below minimum size thresholds. Very small lots or properties with easements may face additional constraints. Our team can assess 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, based on the project scope and local permitting timelines. The approval phase alone can take two to four months in San Jose, so planning ahead matters. Straightforward interior conversions may complete more quickly, while multi-room detached cottages fall toward the upper end of the timeline.
What does ADU construction typically cost?
Costs vary widely based on whether it's a conversion or new construction. Locally, ADU construction typically ranges from $150,000 to $400,000 or more for a standalone backyard unit. Interior conversion projects are generally priced lower, sometimes between $75,000 and $140,000. A detailed estimate can only be given after completing a formal feasibility evaluation.
Is ADU construction difficult to live through while it's underway?
How much the build affects daily life 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. Interior conversions may involve some shared wall work during key milestones. Our team communicates clearly about upcoming work and timelines.
Do I need to leave my home during ADU construction?
For the majority of homeowners, you won't have to vacate your house during ADU construction. Most builds are set up to let you remain on the property throughout the build. There are edge cases if significant structural connections require temporary shutoffs in ways that temporarily impact livability. The team at Brother & Brother Builders will discuss these scenarios 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 can be expected to last as long as the main residence — often several decades with routine maintenance. Longevity is tied to the standard of construction, how consistently minor repairs are addressed, and how proactively issues are resolved over time. Our builds use website commercial-grade materials and follow all code requirements to deliver a structure that stands the test of time.
ADU Construction for Local Homeowners
The communities throughout San Jose provide a wide range of property types that are ideally positioned for ADU construction. Residents in the Rose Garden district have found their lots work well for both attached and detached projects. Communities around the Capitol Expressway corridor are increasingly popular for ADU construction as multigenerational living becomes more common. From neighborhoods near the Guadalupe River Park corridor to those near Branham Lane, our team knows the permitting landscape well.
The City of San Jose's building department applies particular standards for ADU construction that require a builder familiar with local expectations. Proximity to transit corridors can affect how quickly permits are approved for a given ADU project. Our familiarity with these local conditions means more accurate timelines and budgets from design through the final walkthrough.
Schedule Your ADU Construction Consultation Today
If you're ready to explore what an ADU could look like on your lot, Brother & Brother Builders is the team to call. Our experts offer licensed expertise in ADU construction across a wide range of project types — from simple garage conversions to multi-room backyard residences. Every project starts with a thorough and honest property review where we listen to your goals and share clear expectations of what's achievable.
Reach out to our team to schedule a site visit. No matter where you are in the decision-making process, we enjoy discuss timelines, costs, and design possibilities and give 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