Expand Your Home with Professional ADU Construction
Property owners throughout San Jose, CA are realizing that adding an accessory dwelling unit is one of the most rewarding investments they can make. ADU construction creates a versatile new living space on your existing property — whether you want to generate rental income. Brother & Brother Builders has guided hundreds of local homeowners bring these projects to life with craftsmanship and integrity.
The interest in ADU construction has surged 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 provides increased control over how your property works.
At Brother & Brother Builders, we bring years of hands-on experience to every ADU construction build. Our team knows the San Jose building codes, the engineering details, and the aesthetic decisions that make an ADU truly livable. If you've been thinking about what ADU construction could do for 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 self-contained living space — including a kitchen, bathroom, sleeping area, and its own access point — 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 interior space reconfigurations.
Mechanically, the work starts with a comprehensive review of your lot, where our builders evaluate setbacks, zoning, utility access, and structural feasibility. From there, architectural drawings are prepared and submitted to the relevant municipal authority. Once permits are secured, ADU construction enters the physical build phase — which covers everything from foundational work, framing, mechanical systems, weatherproofing, and interior finishing. The result is a fully functional living unit connected to or independent of your main home.
What sets quality ADU construction apart is the level of craftsmanship at every stage. Materials must be selected to match the primary home's aesthetic. Systems like wiring and water supply 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 Benefits ADU Construction
- Higher Resale Potential — ADU construction contributes significant market value to your property, often increasing appraised value substantially 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.
- Housing for Extended Family — ADU construction provides adult children a private, independent living space without losing proximity to the family.
- Personalized Layouts — From modern studio layouts, ADU construction may be customized to your household's priorities.
- Simplified Regulatory Path — Recent state legislation has reduced 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 requiring new development, which contributes to sustainability goals.
- Separate Entrances and Spaces — Unlike a bedroom addition, ADU construction creates a truly separate unit where tenants live autonomously.
- Durable Return on Investment — A well-built ADU continues to produce returns for many years and generates both livable square footage and monetary benefit.
The ADU Construction Process Step by Step
- Initial Property Assessment and Feasibility Review — Our team visits your property to analyze zoning rules, slope conditions, and available square footage. This stage clarifies exactly what ADU types will work before any time is invested in drawings.
- Blueprint Development and Layout Design — Licensed architects and designers create precise architectural drawings reflecting your priorities. Layouts are carefully considered to maximize function and livability.
- Filing for Building Permits — ADU construction in San Jose requires submitting plans to the city's building department for review and approval. We manage this entire process on your behalf, responding to review feedback promptly.
- Ground Prep and Structural Base — Once permits are granted, on-site work kicks off. This involves leveling and prepping the ground, laying the structural base, and establishing utility connections.
- Shell Construction and Exterior Finishing — The structural frame is erected followed by insulation, sheathing, and exterior cladding. At this stage, the ADU takes its visible shape.
- MEP Systems Rough-In — Certified technicians install the water supply, drain lines, and electrical panel that make the ADU ready for occupancy. Every system is reviewed 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 issues the certificate of occupancy and the ADU is ready for use.
Who Is a Good Candidate for ADU Construction?
Homeowners who benefit most from ADU construction often belong to a few recognizable groups. If you own a single-family home 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.
ADU construction also suits someone who runs a small business and wants a detached creative or business space that doesn't interfere with your family's daily life. Landlords and real estate investors who already own residential properties are also well suited for ADU construction, since the long-term value is proven.
Those who should discuss alternatives first include lots that are below minimum size thresholds. Parcels in historic districts or HOA-restricted communities may need a modified approach. Brother & Brother Builders reviews each property individually and honestly to provide realistic options.
ADU Construction Common Questions Answered
How long does ADU construction typically take from start to finish?
The complete duration for ADU construction typically ranges from six to fourteen months, based on the project scope and how quickly approvals come through. City review on its own can take a significant portion of the overall timeline in San Jose, so planning ahead matters. Straightforward interior conversions may complete more quickly, while custom detached builds 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 commonly costs $150,000 to $400,000 or more for a fully custom construction. Attached ADU additions often come in under, sometimes in the $80,000 to $150,000 range. A detailed estimate can only be developed after a full site assessment.
Is ADU construction disruptive while it's underway?
The day-to-day impact depends on the project's location on your property. Standalone ADU projects are generally the least intrusive, since the construction zone is separate. Garage conversions or attached additions may create short-term inconveniences during specific stages like framing or MEP rough-in. We provide advance notice about what to expect at each stage.
Do I need to vacate the property during ADU construction?
In most cases, you do not need to vacate your primary residence during ADU construction. Most job sites are designed so that you remain on the property throughout the build. Exceptions may arise if significant structural connections require temporary shutoffs in ways that require short-term access disruption. Our project managers will walk you through any potential website disruptions during the planning phase.
How long will an ADU built through professional ADU construction hold up?
A well-built ADU should last as long as your primary home — indefinitely with proper upkeep. How long it lasts comes down to the systems installed, whether the unit is properly cared for, and whether systems like roofing and plumbing are serviced regularly. Our builds use commercial-grade materials and build to current California residential standards to protect your investment for the long haul.
ADU Construction for Local Homeowners
San Jose's neighborhoods offer a wide range of property types that are well suited for ADU construction. Homeowners in the Willow Glen neighborhood often discover their properties work well for both attached and detached projects. 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 has project experience in the area.
Local regulatory bodies in this area has developed specific protocols for ADU construction that require a builder familiar with local expectations. Access to infrastructure along thoroughfares like Monterey Road can impact the design approach for a given ADU project. Our familiarity with this region's building landscape means smoother project delivery from design through the final walkthrough.
Start Your ADU Construction Consultation Today
When you want to add an ADU to your property, Brother & Brother Builders is here to help. Our builders provide years of hands-on experience in ADU construction for many different project types — from small attached additions to large custom detached cottages. The process begins with a comprehensive site assessment where we learn what you're trying to accomplish and provide an honest assessment of what's achievable.
Get in touch with our office to set up your consultation. Even if you're just exploring the idea, we enjoy walk through your options, review completed projects and help you take the next step. Building an ADU is a major decision — and we're committed to helping you get it right.
Brother & Brother Builders | 3109 Stevens Creek Boulevard | San Jose CA 95117 | (888) 412-2632