Unlock New Space with Quality ADU Construction
Families in San Jose, CA are discovering that adding an accessory dwelling unit is one of the most rewarding investments they can make. ADU construction opens the door to a flexible new living space on your existing property — whether you want to generate rental income. Brother & Brother Builders has guided hundreds of local read more homeowners turn these plans to life with skill and transparency.
The demand for ADU construction has increased significantly in recent years, and it's easy to understand why. California state law has streamlined permitting for homeowners to construct these secondary units, and local municipalities like San Jose have supported the trend as a way to increase density responsibly. If you're planning a detached backyard cottage, a garage conversion, or an attached addition, ADU construction gives you more 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 knows the San Jose building codes, the engineering considerations, and the planning steps that make an ADU functional. If you've been thinking about what ADU construction could do for your property, this guide will walk you through everything you need to know.
What Is ADU Construction?
ADU construction refers to the process of designing, permitting, and building an accessory dwelling unit on a residential property. An accessory dwelling unit is a fully independent living space — including 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 work starts with a comprehensive review of your lot, where our team evaluate setbacks, zoning, utility access, and structural feasibility. From there, architectural drawings are prepared and submitted to the local building department. Once permits are secured, ADU construction enters the physical build phase — which includes foundation work, framing, roofing, plumbing, electrical, insulation. The result is a move-in-ready living unit attached to or separate from your main home.
What separates excellent ADU construction from an average project is the level of craftsmanship at every stage. Products need to be chosen to match the primary home's aesthetic. Systems like plumbing and electrical must be sized for independent daily use. Brother & Brother Builders handles every ADU construction job with the same high standards we apply to large-scale custom home projects.
Key Advantages ADU Construction
- Increased Property Value — ADU construction adds measurable market value to your property, often increasing appraised value substantially when it's time to sell.
- Revenue Generation — 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 self-contained residence without losing proximity to the family.
- Personalized Layouts — From two-bedroom configurations, ADU construction is adaptable to the intended occupant's lifestyle.
- Simplified Regulatory Path — Recent state legislation has cut down the red tape associated with ADU construction, resulting in a timeline that is faster and less expensive than ever before.
- Efficient Use of Your Lot — Building an ADU uses your existing lot instead of expanding urban sprawl, which supports broader sustainability goals.
- Separate Entrances and Spaces — Unlike a bedroom addition, ADU construction delivers a genuinely independent unit where residents have their own space.
- Durable Return on Investment — A well-built ADU continues to produce returns for decades, providing both livable square footage and monetary benefit.
The ADU Construction Process Step by Step
- Property Walkthrough and Feasibility Check — Our experts review your property to analyze zoning rules, slope conditions, and available square footage. This stage clarifies exactly what can be built before any resources go toward planning.
- Blueprint Development and Layout Design — Our design team create detailed floor plans based on your goals. Every square foot is planned 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. We manage this entire process on your behalf, addressing any city comments promptly.
- Ground Prep and Structural Base — Once permits are granted, on-site work kicks off. This involves leveling and prepping the ground, 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. During this step, the ADU transforms from a concept to a building.
- MEP Systems Rough-In — Licensed subcontractors install the heating, cooling, drainage, and power infrastructure that make the ADU operationally complete. All work is inspected at designated stages throughout ADU construction.
- Interior Finishing and Final Inspections — Trim, appliances, tile, and lighting are fitted and completed to the approved plan. A last official inspection confirms the unit is code-compliant and the ADU is ready for use.
Who Is a Good Candidate for ADU Construction?
Property owners who are best suited from ADU construction typically fall into a few common profiles. If you have a residential property with available square footage under zoning rules, you're already a strong candidate. 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.
Another strong candidate is someone who works from home and wants a private work environment that doesn't interfere with your family's daily life. Landlords and real estate investors who are building a portfolio are also a natural fit for ADU construction, since the long-term value is proven.
Situations where ADU construction may not be the best first step include sites with unusual utility access challenges. Sites with underground infrastructure conflicts may need a modified approach. Our experts will evaluate each property on its own merits to recommend the right path forward.
ADU Construction Frequently Asked Questions
How long does ADU construction typically take from start to finish?
The full timeline for ADU construction usually runs between six to fourteen months, influenced by the type of unit being built and city review schedules. City review on its own can take a significant portion of the overall timeline 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 larger new construction ADUs take longer to complete.
What does ADU construction usually run in terms of budget?
Costs vary widely 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. Garage conversions often come in under, sometimes between $75,000 and $140,000. An accurate budget can only be produced following a thorough property review.
Is ADU construction intrusive while it's underway?
The level of disruption depends on whether you're converting existing space or building new. Standalone ADU projects are usually easier to live alongside, since the construction zone is separate. Garage conversions or attached additions may involve some shared wall work during key milestones. Brother & Brother Builders keeps you informed about upcoming work and timelines.
Do I need to move out during ADU construction?
In most cases, you do not need to vacate your primary residence during ADU construction. The vast majority of projects are set up to let you continue living in the home throughout the build. Exceptions may arise if major utility upgrades affect the main house in ways that require short-term access disruption. Our project managers will walk you through any potential disruptions during the planning phase.
How long will an ADU built through professional ADU construction hold up?
Any ADU built to code with professional oversight is designed to last as long as the main residence — indefinitely with proper upkeep. Longevity is tied to the quality of materials used, how consistently minor repairs are addressed, and if mechanical components are maintained on schedule. Our builds use commercial-grade materials and follow all code requirements to ensure lasting performance.
ADU Construction for San Jose Homeowners
Residential areas across San Jose present a diverse mix of property types that are ideally positioned for ADU construction. Residents in the Rose Garden district have found their lots accommodate detached backyard units nicely. Communities around the Capitol Expressway corridor have seen growing ADU activity as housing demand rises. Whether your property is near downtown San Jose, our team has likely worked nearby.
The City of San Jose's building department follows defined procedures for ADU construction that our team navigates routinely. Location near major arterials like Story Road or Tully Road can impact the design approach for a given ADU project. Our familiarity with these local conditions means more accurate timelines and budgets from kickoff through certificate of occupancy.
Start 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. Our experts offer years of hands-on experience in ADU construction for many different project types — from modest studio builds to fully independent secondary homes. Our approach opens with a comprehensive site assessment where we listen to your goals and share clear expectations of what the project will involve.
Get in touch with our office to schedule a site visit. Even if you're just exploring the idea, we're glad to answer questions, share examples of our work and help you take the next step. 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