Unlock New Space with Expert ADU Construction
Homeowners across San Jose, CA are finding that adding an accessory dwelling unit is one of the most rewarding investments they can make. ADU construction opens the door to a powerful new living space on your existing property — whether you want to house a family member. Brother & Brother Builders has helped hundreds of local homeowners turn these plans to life with skill and care.
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 build these secondary units, and local municipalities like San Jose have encouraged 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 offers greater control over how your property works.
At Brother & Brother Builders, we bring years of hands-on experience to every ADU construction build. Our team is familiar with city and county requirements, the engineering details, and the planning steps that make an ADU beautiful. If you've been thinking about what ADU construction could mean for your property, this guide explains everything you need to know.
What Is ADU Construction?
ADU construction describes 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 — equipped with a kitchen, bathroom, sleeping area, and its own access point — that sits on the same property as a primary residence. ADU construction includes various structural types, including detached backyard units, attached additions, garage conversions, and even interior space reconfigurations.
Mechanically, everything kicks off with a detailed site assessment, where our professionals evaluate property boundaries, available square footage, and infrastructure capacity. 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 includes foundation work, framing, roofing, plumbing, electrical, insulation. The result is a fully functional living unit adjacent to or detached from your main home.
The difference between a good and a great ADU build is the depth of planning at every stage. Materials must be selected to match the primary home's aesthetic. Systems like wiring and water supply must be sized for independent daily use. Brother & Brother Builders treats each project with the same technical discipline we bring to full custom home projects.
Key Reasons to Choose ADU Construction
- Increased Property Value — ADU construction adds measurable market value to your property, often returning more than the build cost 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.
- Multi-Generational Living — ADU construction gives aging parents a comfortable home of their own without moving to another neighborhood.
- Personalized Layouts — From two-bedroom configurations, ADU construction can be tailored to your household's priorities.
- Faster Permitting in California — Recent state legislation has cut down the permitting obstacles associated with ADU construction, creating a path that is faster and more cost-efficient than ever before.
- Responsible Property Development — Building an ADU uses your existing lot instead of requiring new development, which aligns with sustainability goals.
- Independent Living Areas — Unlike a bedroom addition, ADU construction delivers a genuinely independent unit where tenants live autonomously.
- Durable Return on Investment — A well-built ADU holds its value for the long haul by offering both livable square footage and monetary benefit.
The ADU Construction Journey Step by Step
- Initial Property Assessment and Feasibility Review — Our team visits your property to determine what type of ADU is allowed and where it can be placed. This phase answers exactly what's possible before any time is invested in drawings.
- Blueprint Development and Layout Design — Experienced draftspeople create comprehensive blueprints tailored to your needs. Every square foot is planned to optimize daily use.
- Filing for Building Permits — ADU construction in San Jose requires submitting plans to the city's building department for sign-off and verification. Our team handles all submissions on your behalf, responding to review feedback promptly.
- Excavation and Foundation Installation — Once permits are issued, on-site work kicks off. This involves leveling and prepping the ground, completing foundation work, and running initial plumbing and electrical conduits.
- Structural Framing and Weatherproofing — Framing is completed followed by weatherproofing and exterior finish materials. This phase, the ADU takes its visible shape.
- Mechanical, Electrical, and Plumbing Installation — Licensed subcontractors install the heating, cooling, drainage, and power infrastructure that make the ADU fully functional. Every system is reviewed at required milestones throughout ADU construction.
- Interior Completion and City Sign-Off — Trim, appliances, tile, and lighting are installed and finished to the approved plan. A closing municipal review grants legal occupancy status and the unit is officially approved for use.
Who Is a Good Candidate for ADU Construction?
Property owners who are best suited from ADU construction often belong to a few clear categories. If you have a residential property with a backyard, garage, or basement that could be converted, you're already well-positioned. Homeowners hoping to offset mortgage costs 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 private work environment that remains away from 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.
Homeowners who may want to pause and evaluate include sites with unusual utility access challenges. 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 usually take from start to finish?
The total process for ADU construction typically ranges from six to fourteen months, based on the project scope and how quickly approvals come through. The approval phase alone can take a significant portion of the overall timeline in San Jose, so beginning the process sooner rather than later is wise. Straightforward interior conversions may complete more quickly, while custom detached builds take longer to complete.
What does ADU construction usually run in terms of budget?
Budget requirements differ based on whether it's a conversion or new construction. In the San Jose area, ADU construction commonly costs $150,000 to $400,000 or more for a detached new build. Interior conversion projects often come in under, sometimes between $75,000 and $140,000. A detailed estimate can only be developed after a full site assessment.
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 the crew operates at a distance from your living areas. Garage conversions or attached additions may require temporary access during key milestones. We provide advance notice about what to expect at each stage.
Do I need to vacate the property during ADU construction?
Generally speaking, you do not need to vacate your main home during ADU construction. Most builds are structured to allow you stay in your primary unit throughout the build. Exceptions may arise if major utility upgrades affect the main house in ways that briefly affect habitability. The team at Brother & Brother Builders will flag these situations during the kickoff meeting.
How long will an ADU built through professional ADU construction remain in good condition?
A well-built ADU is designed to last as long as the main residence — 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. Brother & Brother Builders specifies residential-grade products rated for longevity and follow all code requirements to ensure lasting performance.
ADU Construction for Local Homeowners
Residential areas across San Jose present a variety of property types that are perfectly suited for ADU construction. Residents in the Rose Garden district often discover their properties work well for both attached and detached projects. Neighborhoods near Blossom Hill Road have seen growing ADU activity as families expand. If you're located closer to Evergreen, our team knows the permitting landscape well.
San Jose's permitting office applies particular standards for ADU construction that our team navigates routinely. Access to infrastructure along thoroughfares like Monterey here Road can impact the design approach for a given ADU project. Brother & Brother Builders' experience across the San Jose permitting environment means fewer surprises from kickoff through certificate of occupancy.
Schedule Your ADU Construction Consultation Today
If you're ready to add an ADU to your property, Brother & Brother Builders is the team to call. Our experts offer licensed expertise in ADU construction for many different project types — from modest studio builds to fully independent secondary homes. Our approach opens with a thorough and honest property review where we understand your vision and give you a realistic picture of what ADU construction on your property will look like.
Reach out to our team to set up your consultation. No matter where you are in the decision-making process, we enjoy walk through your options, review completed projects and make sure you feel confident before committing. This type of project is a meaningful commitment — and our goal is to ensure it delivers real value.
Brother & Brother Builders | 3109 Stevens Creek Boulevard | San Jose CA 95117 | (888) 412-2632