Expand Your Home with Expert ADU Construction
Property owners throughout San Jose, CA are realizing that adding an accessory dwelling unit is one of the smartest investments they can make. ADU construction opens the door to a versatile new living space on your existing property — whether you want to house a family member. Brother & Brother Builders has supported hundreds of local homeowners bring these projects to life with precision and transparency.
The interest in ADU construction has increased significantly in recent years, and it's not hard to see why. California state law now makes it easier for homeowners to build these secondary units, and local municipalities like San Jose have supported the trend as a way to expand the housing supply. Whether you're building 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 apply deep hands-on experience to every ADU construction build. Our team knows the San Jose building codes, the engineering considerations, and the planning steps that make an ADU beautiful. Should you want to learn about what ADU construction could look like on your property, this guide covers everything you need to know.
What Is ADU Construction?
ADU construction refers to the process of engineering, filing for, and completing an accessory dwelling unit on a residential property. An accessory dwelling unit is a complete 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, the process begins with a comprehensive review of your lot, where our professionals evaluate setbacks, zoning, utility access, and structural feasibility. From there, blueprints are prepared and submitted to the local building department. Once the paperwork is cleared, ADU construction transitions to the physical build phase — which includes foundation work, framing, roofing, plumbing, electrical, insulation. The result is a fully functional living unit connected to or independent of your main home.
The difference between a good and a great ADU build is the attention to detail at every stage. Materials must be selected to complement the existing structure. Systems like plumbing and electrical must be sized for independent daily use. Brother & Brother Builders handles every ADU construction job with the same technical discipline we use on major custom home projects.
Key Reasons to Choose ADU Construction
- Increased Property Value — ADU construction delivers real market value to your property, often returning more than the build cost when it's time to sell.
- Revenue Generation — A completed ADU can be rented as a long-term rental or short-term vacation unit, creating ongoing passive income for the homeowner.
- Housing for Extended Family — ADU construction gives aging parents a private, independent living space without losing proximity to the family.
- Customization Options — From two-bedroom configurations, ADU construction may be customized to your household's priorities.
- Faster Permitting in California — Recent state legislation has minimized the red tape associated with ADU construction, creating a path that is faster and more cost-efficient than ever before.
- Responsible Property Development — Building an ADU works within your current footprint instead of expanding urban sprawl, which aligns with sustainability goals.
- Separate Entrances and Spaces — Unlike a bedroom addition, ADU construction produces a fully self-contained unit where occupants have full privacy.
- Lasting Financial Benefit — A well-built ADU remains an asset for decades, providing both functional space and financial upside.
The ADU Construction Procedure Step by Step
- Site Evaluation and Zoning Analysis — Our team visits your property to evaluate setbacks, lot coverage limits, and utility connections. This phase answers exactly what's possible before any money is spent on design.
- Custom Design and Architectural Planning — Experienced draftspeople create comprehensive blueprints based on your goals. Layouts are carefully considered to optimize daily use.
- 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, addressing any city comments promptly.
- Site Preparation and Foundation Work — Once permits are issued, the build starts. This covers land preparation, pouring the concrete foundation, and establishing utility connections.
- Shell Construction and Exterior Finishing — Walls and roof systems go up followed by weatherproofing and exterior finish materials. At this stage, the ADU becomes recognizable as a structure.
- Mechanical, Electrical, and Plumbing Installation — Certified technicians install the plumbing lines, electrical wiring, and HVAC systems that make the ADU fully functional. Every system is reviewed at designated stages throughout ADU construction.
- Finishes, Fixtures, and Final Walkthrough — Flooring, cabinetry, fixtures, paint are placed and inspected to the agreed design. A closing municipal review grants legal occupancy status and your new space is cleared 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 are a homeowner with available square footage under zoning rules, you're already a strong candidate. 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 separate office or studio space that remains away from your family's daily life. Landlords and real estate investors who already own residential properties are also prime candidates for ADU construction, since rental income frequently offsets build costs.
Homeowners who may want to pause here and evaluate include sites with unusual utility access challenges. Parcels in historic districts or HOA-restricted communities may face additional constraints. Our experts will evaluate each property individually and honestly to advise you on what's feasible.
ADU Construction Frequently Asked Questions
How long does ADU construction generally take from start to finish?
The full timeline for ADU construction commonly spans six to fourteen months, based on the project scope and local permitting timelines. Permitting alone can take several months in San Jose, so planning ahead matters. Smaller detached units can move faster, while larger new construction ADUs take longer to complete.
What does ADU construction cost in San Jose?
Costs vary widely based on the type and size of the ADU. Locally, ADU construction typically ranges from $150,000 to $400,000 or more for a fully custom construction. Garage conversions are generally priced lower, sometimes starting around $80,000 depending on scope. A detailed estimate can only be developed after a formal feasibility evaluation.
Is ADU construction disruptive while it's underway?
The day-to-day impact depends on whether you're converting existing space or building new. New construction in the rear yard are usually easier to live alongside, since the crew operates at a distance from your living areas. Garage conversions or attached additions may require temporary access during certain phases of construction. Brother & Brother Builders keeps you informed about any phases that may affect your routine.
Do I need to move out during ADU construction?
Generally speaking, you do not need to vacate your primary residence during ADU construction. The vast majority of projects are structured to allow you continue living in the home throughout the build. Certain situations could require a brief departure if significant structural connections require temporary shutoffs in ways that temporarily impact livability. Our construction supervisors will discuss these scenarios during the pre-construction consultation.
How long will an ADU built through professional ADU construction hold up?
A well-built ADU can be expected to last as long as the main residence — often several decades with routine maintenance. How long it lasts comes down to the standard of construction, how well routine maintenance is performed, and how proactively issues are resolved over time. We select high-quality components and follow all code requirements to deliver a structure that stands the test of time.
ADU Construction for San Jose Homeowners
San Jose's neighborhoods offer a wide range of property types that are perfectly suited for ADU construction. Homeowners in the Willow Glen neighborhood frequently see their parcels are well configured for ADU builds. The Berryessa area have seen growing ADU activity as housing demand rises. Whether your property is near downtown San Jose, our team has project experience in the area.
San Jose's permitting office applies particular standards for ADU construction that experienced builders know well. Location near major arterials like Story Road or Tully Road can influence utility connection requirements for a given ADU project. Our team's knowledge of the San Jose permitting environment means more accurate timelines and budgets from design through the final walkthrough.
Book Your ADU Construction Consultation Today
When you want to move forward with ADU construction, Brother & Brother Builders is ready to guide you. Our builders provide years of hands-on experience in ADU construction for many different project types — from simple garage conversions to multi-room backyard residences. The process begins with a detailed, no-pressure consultation where we learn what you're trying to accomplish and share clear expectations of what's achievable.
Reach out to our team to begin the conversation. Even if you're just exploring the idea, we enjoy answer questions, share examples of our work and help you take the next step. 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