Expand Your Home with Professional ADU Construction
Families in 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 flexible new living space on your existing property — whether you want to house a family member. Brother & Brother Builders has guided hundreds of local homeowners bring these projects to life with skill and care.
The popularity of ADU construction has surged in recent years, and it's no mystery. California state law now makes it easier for homeowners to construct these secondary units, and local municipalities like San Jose have embraced 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 provides increased 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. If you've been thinking about what ADU construction could mean for your property, this guide explains everything you need to know.
What Is the ADU Construction Process?
ADU construction describes the process of planning, approving, and constructing an accessory dwelling unit on a residential property. An accessory dwelling unit is a self-contained living space — featuring a kitchen, bathroom, sleeping area, and its own access point — 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 interior space reconfigurations.
Mechanically, everything kicks off with a comprehensive review of your lot, where our builders evaluate property boundaries, available square footage, and infrastructure capacity. From there, design plans are prepared and submitted to the local building department. Once approvals are in place, ADU construction moves into the physical build phase — which includes foundation work, framing, mechanical systems, weatherproofing, and interior finishing. The result is a move-in-ready 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. 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 handles every ADU construction job with the same professional rigor we bring to full custom home projects.
Key Advantages ADU Construction
- Increased Property Value — ADU construction adds measurable market value to your property, often generating strong equity gains 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 open-plan one-bedrooms, ADU construction can be tailored to your specific needs.
- Streamlined Approval Process — Recent state legislation has cut down the permitting obstacles associated with ADU construction, making the process that is faster and more affordable than ever before.
- Efficient Use of Your Lot — Building an ADU uses your existing lot instead of consuming open land, which aligns with sustainability goals.
- Independent Living Areas — Unlike a bedroom addition, ADU construction creates a truly separate unit where tenants live autonomously.
- Lasting Financial Benefit — A well-built ADU remains an asset for many years and generates both functional space and financial upside.
The ADU Construction Procedure Step by Step
- Property Walkthrough and Feasibility Check — Our experts review your property to evaluate setbacks, lot coverage limits, and utility connections. This phase answers exactly what can be built before any resources go toward planning.
- Architectural Drafting and Space Planning — Licensed architects and designers create detailed floor plans reflecting your priorities. Space is thoughtfully allocated to maximize function and livability.
- Permit Submission and Municipal Review — 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, responding to review feedback promptly.
- Excavation and Foundation Installation — Once permits are issued, on-site work kicks off. This covers land preparation, pouring the concrete foundation, and running initial plumbing and electrical conduits.
- Framing, Roofing, and Exterior Work — Framing is completed followed by weatherproofing and exterior finish materials. At this stage, the ADU transforms from a concept to a building.
- Interior Systems and Infrastructure — Certified technicians install the plumbing lines, electrical wiring, and HVAC systems that make the ADU operationally complete. Inspections are completed at required milestones throughout ADU construction.
- Interior Completion and City Sign-Off — Flooring, cabinetry, fixtures, paint are placed and inspected to the approved plan. A final city inspection grants legal occupancy status and your new space is cleared for use.
Who Is a Strong Candidate for ADU Construction?
Property owners who are best suited from ADU construction typically fall into a few clear categories. If you have a residential property with enough lot space to meet setback requirements, you're already in a good starting place. 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 runs a small business and wants a detached creative or read more business space that doesn't interfere with your family's daily life. Property investors and rental owners who are building a portfolio are also a natural fit 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. Sites with underground infrastructure conflicts may face additional constraints. Our experts will evaluate each property on its own merits to advise you on what's feasible.
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. Permitting alone can take a significant portion of the overall timeline in San Jose, so planning ahead matters. Smaller detached units often finish in the lower end of the range, while larger new construction ADUs require more time.
What does ADU construction typically cost?
Pricing depends on many factors based on whether it's a conversion or new construction. For most projects in this region, ADU construction commonly costs $150,000 to $400,000 or more for a standalone backyard unit. Interior conversion projects are generally priced lower, sometimes starting around $80,000 depending on scope. A precise cost projection can only be developed after 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. Standalone ADU projects are generally the least intrusive, since the construction zone is separate. Interior conversions may require temporary access during key milestones. We provide advance notice about upcoming work and timelines.
Do I need to vacate the property during ADU construction?
Generally speaking, you won't have to vacate your main home during ADU construction. Most job sites are designed so that you continue living in the home throughout the build. Certain situations could require a brief departure if major utility upgrades affect the main house in ways that briefly affect habitability. 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?
A well-built ADU should last as long as any standard residential structure — typically 50 years or more. How long it lasts comes down to the standard of construction, how well routine maintenance is performed, and whether systems like roofing and plumbing are serviced regularly. Our builds use residential-grade products rated for longevity and comply with all local building codes to ensure lasting performance.
ADU Construction for San Jose Homeowners
Residential areas across San Jose present a wide range of property types that are perfectly suited for ADU construction. Property owners near the Almaden Valley area frequently see their parcels accommodate detached backyard units nicely. The Berryessa area are seeing more homeowners add secondary units as multigenerational living becomes more common. From neighborhoods near the Guadalupe River Park corridor to those near Branham Lane, our team has project experience in the area.
San Jose's permitting office has developed specific protocols for ADU construction that our team navigates routinely. Access to infrastructure along thoroughfares like Monterey Road can influence utility connection requirements for a given ADU project. Brother & Brother Builders' experience across these local conditions means more accurate timelines and budgets 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 ready to guide you. We bring years of hands-on experience in ADU construction for many different project types — from modest studio builds to fully independent secondary homes. The process begins with a comprehensive site assessment where we learn what you're trying to accomplish and share clear expectations of what ADU construction on your property will look like.
Contact Brother & Brother Builders to begin the conversation. No matter where you are in the decision-making process, we're glad to answer questions, share examples of our work and make sure you feel confident before committing. This type of project is a meaningful commitment — 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