Expand Your Home with Professional ADU Construction
Families in San Jose, CA are finding that adding an accessory dwelling unit is one of the smartest investments they can make. ADU construction provides a versatile new living space on your existing property — whether you want to house a family member. Brother & Brother Builders has guided hundreds of local homeowners see these visions to life with skill and integrity.
The popularity of ADU construction has grown rapidly 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 expand the housing supply. If you're planning a detached backyard cottage, a garage conversion, or an attached addition, ADU construction offers greater control over how your property serves your household.
At Brother & Brother Builders, we bring years of hands-on experience to every ADU construction project. Our team understands the local permitting process, the engineering details, and the planning steps that make an ADU truly livable. If you've been thinking about what ADU construction could do for your property, this guide explains 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 — featuring a kitchen, bathroom, sleeping area, and its own access point — that exists on the same lot as a primary residence. ADU construction comes in multiple configurations, including detached backyard units, attached additions, garage conversions, and even basement or interior conversions.
Mechanically, everything kicks off with a comprehensive review of your lot, where our builders evaluate lot dimensions, existing structures, soil conditions, and local code requirements. From there, blueprints are prepared and submitted to the local building department. Once permits are secured, ADU construction enters the physical build phase — which encompasses site preparation, framing, mechanical systems, weatherproofing, and interior finishing. The result is a completely finished living unit adjacent to or detached from your main home.
What sets quality ADU construction apart is the level of craftsmanship at every stage. Materials must be selected to align with the neighborhood's character. Systems like plumbing and electrical must be designed to handle full-time occupancy. Brother & Brother Builders handles every ADU construction job with the same high standards 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.
- Revenue Generation — A completed ADU is leasable 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 comfortable home of their own without losing proximity to the family.
- Customization Options — From two-bedroom configurations, ADU construction is adaptable to your specific needs.
- Simplified Regulatory Path — Recent state legislation has minimized the permitting obstacles associated with ADU construction, creating a path that is faster and more affordable than ever before.
- Responsible Property Development — 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 creates a truly separate unit where occupants have full privacy.
- Durable Return on Investment — A well-built ADU holds its value for many years and generates both livable square footage and monetary benefit.
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.
- Blueprint Development and Layout Design — Our design team create detailed floor plans tailored to your needs. Every square foot is planned to optimize daily use.
- Filing for Building Permits — 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 issued, on-site work kicks off. This covers land preparation, completing foundation work, and establishing utility connections.
- Shell Construction and Exterior Finishing — Framing is completed followed by insulation, sheathing, and exterior cladding. This phase, the ADU transforms from a concept to a building.
- Interior Systems and Infrastructure — Licensed subcontractors install the heating, cooling, drainage, and power infrastructure that make the ADU ready for occupancy. Inspections are completed at designated stages throughout ADU construction.
- Interior Finishing and Final Inspections — Flooring, cabinetry, fixtures, paint are placed and inspected to the approved plan. A last official inspection issues the certificate of occupancy and your new space is cleared for use.
Who Is a Strong Candidate for ADU Construction?
Homeowners who benefit most from ADU construction generally fit within a few recognizable groups. If you are a homeowner with available square footage under zoning rules, you're already in a good starting place. Homeowners hoping to offset mortgage costs 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. Landlords and real estate investors who are building a portfolio are also well suited for ADU construction, since rental income frequently offsets build costs.
Situations where ADU construction may not be the best first step include properties with significant setback limitations. Sites with underground infrastructure conflicts may need a modified approach. Our team can assess each property individually and honestly to recommend the right path forward.
ADU Construction FAQ
How long does ADU construction usually take from start to finish?
The total process 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 beginning the process sooner rather than later is wise. Smaller detached units often finish in the lower end of the range, while multi-room detached cottages fall toward the upper end of the timeline.
What does ADU construction cost in San Jose?
Costs vary widely based on project complexity and finishes selected. 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 detailed estimate can only be given after completing a thorough property review.
Is ADU construction intrusive while it's underway?
How much the build affects daily life depends on the project's location on your property. Detached backyard builds are typically less disruptive, since work happens away from the main house. Interior conversions may create short-term inconveniences during specific stages like framing or MEP rough-in. Our team communicates clearly about what to expect at each stage.
Do I need to vacate the property during ADU construction?
For the majority of homeowners, you are not required to vacate your house during ADU construction. Most builds are structured to allow you continue living in the home throughout the process. Certain situations could require a brief adu construction near San Jose departure if interior conversion work touches shared systems 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 last?
An ADU constructed with quality materials is designed to last as long as the main residence — often several decades with routine maintenance. How long it lasts comes down to the systems installed, how well routine maintenance is performed, and if mechanical components are maintained on schedule. We select residential-grade products rated for longevity and follow all code requirements to ensure lasting performance.
ADU Construction for Local Homeowners
The communities throughout San Jose provide a wide range of property types that are ideally positioned for ADU construction. Property owners near the Almaden Valley area often discover their properties accommodate detached backyard units nicely. Neighborhoods near Blossom Hill Road 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 likely worked nearby.
Local regulatory bodies in this area applies particular standards 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. Our team's knowledge of this region's building landscape means fewer surprises from kickoff through certificate of occupancy.
Book Your ADU Construction Planning Session Today
Should you be thinking about how to move forward with ADU construction, Brother & Brother Builders is here to help. Our builders provide proven skills in ADU construction for many different project types — from small attached additions to large custom detached cottages. Our approach opens with a thorough and honest property review where we understand your vision and provide an honest assessment of what's achievable.
Get in touch with our office to set up your consultation. No matter where you are in the decision-making process, we're glad to answer questions, share examples of our work and give you the clarity you need to move forward. 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