Unlock New Space with Professional ADU Construction
Homeowners across San Jose, CA are discovering that adding an accessory dwelling unit is one of the smartest 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 supported hundreds of local homeowners see these visions to life with skill and care.
The demand for ADU construction has grown rapidly in recent years, and it's no mystery. California state law now makes it easier for homeowners to build these secondary units, and local municipalities like San Jose have supported the trend as a way to address housing needs. 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 job. Our team knows the San Jose building codes, the engineering considerations, and the aesthetic decisions that make an ADU truly livable. 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 the ADU Construction Process?
ADU construction describes the process of engineering, filing for, and completing an accessory dwelling unit on a residential property. An accessory dwelling unit is a complete living space — featuring a kitchen, bathroom, sleeping area, and its own access point — 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 work starts with a detailed site assessment, where our builders evaluate property boundaries, available square footage, and infrastructure capacity. From there, blueprints are prepared and submitted to the city for permit approval. Once permits are secured, ADU construction moves into the physical build phase — which includes foundation work, framing, mechanical systems, weatherproofing, and interior finishing. 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. Products need to be chosen to complement the existing structure. Systems like HVAC and drainage must be sized for independent daily use. Brother & Brother Builders treats each project with the same professional rigor we use on major custom home projects.
Key Reasons to Choose ADU Construction
- Boosted Home Equity — ADU construction delivers real market value to your property, often increasing appraised value substantially when it's time to sell.
- Monthly Cash Flow — A completed ADU can be rented as a long-term rental or short-term vacation unit, generating steady monthly revenue for the homeowner.
- Housing for Extended Family — ADU construction provides adult children a comfortable home of their own without leaving the property.
- Customization Options — From two-bedroom configurations, ADU construction may be customized to your household's priorities.
- Simplified Regulatory Path — 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.
- Efficient Use of Your Lot — Building an ADU maximizes the land you already own instead of expanding urban sprawl, which supports broader sustainability goals.
- Separate Entrances and Spaces — Unlike a bedroom addition, ADU construction creates a truly separate unit where residents have their own space.
- Durable Return on Investment — A well-built ADU remains an asset for many years and generates both livable square footage and monetary benefit.
The ADU Construction Journey Step by Step
- Site Evaluation and Zoning Analysis — Our builders assess your property to analyze zoning rules, slope conditions, and available square footage. This step tells you exactly what's possible before any money is spent on design.
- Custom Design and Architectural Planning — Experienced draftspeople create precise architectural drawings based on your goals. Space is thoughtfully allocated to optimize daily use.
- Permitting and City Approval — 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, resolving any revision requests promptly.
- Excavation and Foundation Installation — Once permits are issued, the build starts. This involves leveling and prepping the ground, laying the structural base, and running initial plumbing and electrical conduits.
- Structural Framing and Weatherproofing — Walls and roof systems go up followed by roofing, siding, windows, and exterior doors. At this stage, the ADU becomes recognizable as a structure.
- Mechanical, Electrical, and Plumbing Installation — Certified technicians 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 Finishing and Final Inspections — Countertops, hardware, finishes, and fixtures are fitted and completed to your specifications. A final city inspection issues the certificate of occupancy and the unit is officially approved for use.
Who Is a Good Candidate for ADU Construction?
People who see the greatest return from ADU construction generally fit within a few common profiles. If you are a homeowner 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 navigating multigenerational living situations.
ADU construction also suits 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 want to maximize their land are also well suited for ADU construction, since the return on investment is well-documented.
Those who should discuss alternatives first include lots that are below minimum size thresholds. Very small lots or properties with easements may need a modified approach. Our team can assess 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 typically ranges from six to fourteen months, based on the project scope and local permitting timelines. Permitting alone can take several months in San Jose, so beginning the process sooner rather than later is wise. Simpler garage conversions often finish in the lower end of the range, while multi-room detached cottages take longer to complete.
What does ADU construction typically cost?
Costs vary widely based on the type and size of the ADU. Locally, ADU construction generally falls between $150,000 to $400,000 or more for a detached new build. Interior conversion projects often come in under, sometimes in the $80,000 to $150,000 range. A precise cost projection can only be developed after a thorough property review.
Is ADU construction disruptive 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 the construction zone is separate. Garage conversions or attached additions may involve some shared wall work during certain phases of construction. Our team communicates clearly about upcoming work and timelines.
Do I need to leave my home during ADU construction?
In most cases, you are not required to vacate your main home during ADU construction. Most job sites are designed so that you remain on the property throughout the process. There are edge cases if major utility upgrades affect the main house in ways that briefly affect habitability. Our construction supervisors will discuss these scenarios during the planning phase.
How long will an ADU built through professional ADU construction remain in good condition?
An ADU constructed with quality materials can be expected to last as long as any standard residential structure — often several decades with routine maintenance. Durability depends to the quality of materials used, how consistently minor repairs are addressed, and how proactively issues are resolved over time. Our builds use residential-grade products rated for longevity and build to current California residential standards to protect your investment for the long haul.
ADU Construction for Local Homeowners
The communities throughout San Jose provide a diverse mix of property types that are perfectly suited 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 seeing more homeowners add secondary units as families expand. From neighborhoods near the Guadalupe River Park corridor to those near Branham Lane, our team has likely worked nearby.
The City of San Jose's building department has developed specific protocols for ADU construction that experienced builders know well. Location near major arterials like Story Road or Tully Road can impact the design approach for a given ADU project. Brother & Brother Builders' experience across these local conditions means smoother project delivery from design through the final walkthrough.
Book 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 licensed expertise in ADU construction for many different project types — from modest studio builds to large custom detached cottages. Every project starts with a thorough and honest property review where we listen to your goals and give you a realistic picture of what ADU construction on your property will look like.
Get in touch San Jose adu construction with our office to set up your consultation. No matter where you are in the decision-making process, we're glad to discuss timelines, costs, and design possibilities 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