Expand Your Home with Quality ADU Construction
Homeowners across San Jose, CA are finding that adding an accessory dwelling unit is one of the smartest 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 helped hundreds of local homeowners turn these plans to life with skill and care.
The popularity of ADU construction has increased significantly in recent years, and it's not hard to see why. California state law has simplified the process for homeowners to construct these secondary units, and local municipalities like San Jose have supported the trend as a way to address housing needs. If you're planning a detached backyard cottage, a garage conversion, or an attached addition, ADU construction provides increased control over how your property serves your household.
At Brother & Brother Builders, we draw on extensive hands-on experience to every ADU construction build. Our team is familiar with city and county requirements, the engineering considerations, and the planning steps that make an ADU truly livable. If you've been thinking about what ADU construction could look like on your property, this guide explains everything you need to know.
What Is the ADU Construction Process?
ADU construction involves the process of designing, permitting, and building an accessory dwelling unit on a residential property. An accessory dwelling unit is a self-contained 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 can take several forms, including detached backyard units, attached additions, garage conversions, and even basement or interior conversions.
Mechanically, the process begins with a detailed site assessment, where our builders evaluate property boundaries, available square footage, and infrastructure capacity. From there, design plans are prepared and submitted to the local building department. Once the paperwork is cleared, ADU construction moves into the physical build phase — which encompasses site preparation, framing, roofing, plumbing, electrical, insulation. The result is a move-in-ready 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. Products need to be chosen to align with the neighborhood's character. Systems like wiring and water supply must be designed to handle full-time occupancy. Brother & Brother Builders approaches every build with the same professional rigor 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.
- 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 provides adult children a comfortable home of their own without leaving the property.
- Design Flexibility — From modern studio layouts, ADU construction can be tailored to your household's priorities.
- Simplified Regulatory Path — Recent state legislation has reduced the barriers and delays associated with ADU construction, resulting in a timeline that is faster and more cost-efficient than ever before.
- Efficient Use of Your Lot — Building an ADU uses your existing lot instead of consuming open land, which aligns with sustainability goals.
- Independent Living Areas — Unlike a bedroom addition, ADU construction creates a truly separate unit where occupants have full privacy.
- Long-Term Investment Security — A well-built ADU continues to produce returns for many years and generates both usable housing and equity growth.
The ADU Construction Journey Step by Step
- Property Walkthrough and Feasibility Check — Our team visits your property to evaluate setbacks, lot coverage limits, and utility connections. This stage clarifies exactly what can be built before any resources go toward planning.
- Architectural Drafting and Space Planning — Experienced draftspeople create comprehensive blueprints based on your goals. Layouts are carefully considered to maximize function and livability.
- Permit Submission and Municipal Review — ADU construction in San Jose requires submitting plans to the city's building department for review and approval. Brother & Brother Builders coordinates the permitting on your behalf, resolving any revision requests promptly.
- Site Preparation and Foundation Work — Once permits are granted, physical construction begins. This involves leveling and prepping the ground, pouring the concrete foundation, and running initial plumbing and electrical conduits.
- Shell Construction and Exterior Finishing — The structural frame is erected followed by weatherproofing and exterior finish materials. This phase, the ADU takes its visible shape.
- Mechanical, Electrical, and Plumbing Installation — Skilled tradespeople install the plumbing lines, electrical wiring, and HVAC systems that make the ADU fully functional. Every system is reviewed at each code checkpoint throughout ADU construction.
- Finishes, Fixtures, and Final Walkthrough — Trim, appliances, tile, and lighting are installed and finished to the approved plan. A closing municipal review grants legal occupancy status and your new space is cleared for use.
Who Is a Strong Candidate for ADU Construction?
People who see the greatest return from ADU construction often belong to a few recognizable groups. If you have a residential property with enough lot space to meet setback requirements, you're already well-positioned. Homeowners wanting to add a revenue stream through rental are among the most common ADU construction clients, along with families navigating multigenerational living situations.
You may also be someone who works from home and wants a separate office or studio space that is distinct from your family's daily life. Real estate-minded homeowners who already own residential properties are also a natural fit for ADU construction, since the return on investment is well-documented.
Those who should discuss alternatives first include lots that are below minimum size thresholds. Very small lots or properties with easements may need a modified approach. Our team can assess each property on its own merits to provide realistic options.
ADU Construction FAQ
How long does ADU construction generally take from start to finish?
The full timeline for ADU construction commonly spans six to fourteen months, depending on design complexity and how quickly approvals come through. Permitting alone can take a significant portion of the overall timeline in San Jose, so starting early is important. Smaller detached units often finish in the lower end of the range, while custom detached builds require more time.
What does ADU construction usually run in terms of budget?
Costs vary widely 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 standalone backyard unit. Attached ADU additions are generally priced lower, sometimes in the $80,000 to $150,000 range. A detailed estimate can only be given after completing a full site assessment.
Is ADU construction intrusive while it's underway?
How much the build affects daily life depends on where the ADU is being built. Detached backyard builds are generally the least intrusive, since work happens away from the main house. Projects that connect to the main structure may create short-term inconveniences during key milestones. 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 won't have to vacate your main home during ADU construction. Most builds are structured to allow you stay in your primary unit throughout the build. Certain situations website could require a brief departure if major utility upgrades affect the main house in ways that temporarily impact livability. Our construction supervisors will walk you through any potential 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 any standard residential structure — typically 50 years or more. How long it lasts comes down to the quality of materials used, how well routine maintenance is performed, and how proactively issues are resolved over time. Brother & Brother Builders specifies residential-grade products rated for longevity 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 diverse mix of property types that are perfectly suited for ADU construction. Property owners near the Almaden Valley area have found their lots work well for both attached and detached projects. Neighborhoods near Blossom Hill Road are seeing more homeowners add secondary units as housing demand rises. Whether your property is near downtown San Jose, our team knows the permitting landscape well.
The City of San Jose's building department follows defined procedures for ADU construction that require a builder familiar with local expectations. 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 this region's building landscape means fewer surprises from design through the final walkthrough.
Start Your ADU Construction Consultation Today
When you want to explore what an ADU could look like on your lot, Brother & Brother Builders is here to help. Our builders provide proven skills in ADU construction including all types of project types — from simple garage conversions to multi-room backyard residences. Every project starts with a thorough and honest property review where we understand your vision and share clear expectations of what's achievable.
Reach out to our team to set up your consultation. Whether you're in the early stages of planning, we enjoy discuss timelines, costs, and design possibilities and make sure you feel confident before committing. ADU construction is a significant investment — and our goal is to ensure it delivers real value.
Brother & Brother Builders | 3109 Stevens Creek Boulevard | San Jose CA 95117 | (888) 412-2632