Unlock New Space 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 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 see these visions to life with precision and care.
The demand for ADU construction has increased significantly in recent years, and it's no mystery. California state law now makes it easier for homeowners to add these secondary units, and local municipalities like San Jose have supported the trend as a way to address housing needs. Whether you're building 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 apply deep hands-on experience to every ADU construction build. Our team is familiar with city and county requirements, the engineering requirements, and the design choices that make an ADU functional. If you've been thinking about what ADU construction could mean for your property, this guide will walk you through everything you need to know.
What Is an ADU Build?
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 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, the work starts with a comprehensive review of your lot, where our team evaluate property boundaries, available square footage, and infrastructure capacity. From there, design plans are prepared and submitted to the relevant municipal authority. Once the paperwork is cleared, ADU construction enters the physical build phase — which includes foundation work, framing, HVAC, drywall, flooring, and exterior finishes. The result is a move-in-ready 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. Products need to be chosen to match the primary home's aesthetic. Systems like HVAC and drainage must be designed to handle full-time occupancy. Brother & Brother Builders handles every ADU construction job with the same high standards we apply to large-scale custom home projects.
Key Benefits ADU Construction
- Increased Property Value — ADU construction delivers real market value to your property, often generating strong equity gains when it's time to sell.
- Rental Income Potential — A completed ADU is leasable as a long-term rental or short-term vacation unit, generating steady monthly revenue for the homeowner.
- Multi-Generational Living — ADU construction offers family members a private, independent living space without losing proximity to the family.
- Customization Options — From open-plan one-bedrooms, ADU construction may be customized to your household's priorities.
- Faster Permitting in California — Recent state legislation has reduced the barriers and delays associated with ADU construction, making the process that is faster and more affordable than ever before.
- Responsible Property Development — Building an ADU uses your existing lot instead of requiring new development, which contributes to sustainability goals.
- Independent Living Areas — Unlike a bedroom addition, ADU construction delivers a genuinely independent unit where occupants have full privacy.
- Durable Return on Investment — A well-built ADU holds its value for the long haul by offering both usable housing and equity growth.
The ADU Construction Process Step by Step
- Property Walkthrough and Feasibility Check — Our builders assess your property to analyze zoning rules, slope conditions, and available square footage. This stage clarifies exactly what can be built before any time is invested in drawings.
- Blueprint Development and Layout Design — Our design team create detailed floor plans tailored to your needs. Every square foot is planned to maximize function and livability.
- Filing for Building Permits — ADU construction in San Jose involves filing drawings to the city's building department for inspection and clearance. Brother & Brother Builders coordinates the permitting on your behalf, resolving any revision requests promptly.
- Excavation and Foundation Installation — Once permits are granted, the build starts. This includes grading the site, completing foundation work, and running initial plumbing and electrical conduits.
- Framing, Roofing, and Exterior Work — The structural frame is erected followed by weatherproofing and exterior finish materials. During this step, the ADU takes its visible shape.
- MEP Systems Rough-In — Licensed subcontractors install the plumbing lines, electrical wiring, and HVAC systems that make the ADU fully functional. Inspections are completed at each code checkpoint throughout ADU construction.
- Finishes, Fixtures, and Final Walkthrough — Countertops, hardware, finishes, and fixtures are placed and inspected to the approved plan. A last official inspection confirms the unit is code-compliant and your new space is cleared for use.
Who Is a Right Fit for ADU Construction?
Property owners who are best suited from ADU construction often belong to a few common profiles. If you own a single-family home 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 motivated ADU construction clients, along with families navigating multigenerational living situations.
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 prime candidates for ADU construction, since the long-term value is proven.
Situations where ADU construction may not be the best first step include properties with significant setback limitations. Sites with underground infrastructure conflicts may require additional review. Our experts will evaluate each property case by case to provide realistic options.
ADU Construction Common Questions Answered
How long does ADU construction typically 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 can move faster, while multi-room detached cottages fall toward the upper end of the timeline.
What does ADU construction usually run in terms of budget?
Costs vary widely based on the type and size of the ADU. For most projects in this region, ADU construction typically ranges from $150,000 to $400,000 or more for a fully custom construction. Interior conversion projects are generally priced lower, sometimes starting around $80,000 depending on scope. An accurate budget 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 whether you're converting existing space or building new. Standalone ADU projects are usually easier to live alongside, since the construction zone is separate. Garage conversions or attached additions may require temporary access during specific stages like framing or MEP rough-in. Our team communicates clearly about any phases that may affect your routine.
Do I need to move out during ADU construction?
For the majority of homeowners, you do not need to vacate your main home during ADU construction. The vast majority of projects are designed so that you remain on the property throughout the process. Certain situations could require a brief departure if interior conversion work touches shared systems 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 last?
Any ADU built to code with professional oversight should last as long as your primary home — typically 50 years or more. How long it lasts comes down to the systems installed, how well routine maintenance is performed, and if mechanical components are maintained on schedule. Brother & Brother Builders specifies high-quality components and build to current California residential standards to ensure lasting performance.
ADU Construction for Local Homeowners
The communities throughout San Jose provide a variety of property types that are perfectly suited for ADU construction. Property owners near the Almaden Valley area frequently see their parcels are well configured for ADU builds. The Berryessa area have seen growing ADU activity as multigenerational living becomes more common. If you're located closer to Evergreen, our team has likely worked nearby.
San Jose's permitting office applies particular standards for ADU construction that require a builder familiar with local expectations. Proximity to transit corridors can impact the design approach for a given ADU project. Our team's knowledge of these local conditions means fewer surprises from kickoff through certificate of occupancy.
Schedule Your ADU Construction Assessment Today
When you want to explore what an ADU could look like on your lot, Brother & Brother Builders is here to help. We bring licensed expertise in ADU construction across a wide range of project types — from small attached additions to multi-room backyard residences. Our approach read more opens with a thorough and honest property review where we listen to your goals and share clear expectations of what the project will involve.
Get in touch with our office to set up your consultation. Even if you're just exploring the idea, we enjoy discuss timelines, costs, and design possibilities and make sure you feel confident before committing. ADU construction is a significant investment — and we want to make sure it's the right one for you.
Brother & Brother Builders | 3109 Stevens Creek Boulevard | San Jose CA 95117 | (888) 412-2632