Expand Your Home with Quality ADU Construction
Property owners throughout San Jose, CA are discovering that adding an accessory dwelling unit is one of the most practical investments they can make. ADU construction creates a flexible 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 precision and transparency.
The demand for 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 add these secondary units, and local municipalities like San Jose have supported the trend as a way to expand the housing supply. Whether you want to build a detached backyard cottage, a garage conversion, or an attached addition, ADU construction provides increased control over how your property functions.
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 details, and the aesthetic decisions that make an ADU beautiful. If you've been thinking about what ADU construction could do for your property, this guide explains everything you need to know.
What Is an ADU Build?
ADU construction involves 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 — including a kitchen, bathroom, sleeping area, and its own entrance — 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 below-grade dwelling units.
Mechanically, the work starts with a detailed site assessment, where our team evaluate setbacks, zoning, utility access, and structural feasibility. From there, architectural drawings are prepared and submitted to the local building department. Once permits are secured, ADU construction transitions to the physical build phase — which covers everything from foundational work, framing, mechanical systems, weatherproofing, and interior finishing. The result is a move-in-ready living unit adjacent to or detached from your main home.
What separates excellent ADU construction from an average project is the level of craftsmanship at every stage. Materials must be selected to complement the existing structure. Systems like wiring and water supply must be designed to handle full-time occupancy. Brother & Brother Builders handles every ADU construction job 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 generating strong equity gains when it's time to sell.
- Monthly Cash Flow — A completed ADU may be listed 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 moving to another neighborhood.
- Personalized Layouts — From modern studio layouts, ADU construction may be customized to your specific needs.
- Simplified Regulatory Path — Recent state legislation has minimized the permitting obstacles associated with ADU construction, resulting in a timeline that is faster and more affordable than ever before.
- Sustainable Land Use — Building an ADU works within your current footprint instead of consuming open land, which supports broader sustainability goals.
- Separate Entrances and Spaces — Unlike a bedroom addition, ADU construction delivers a genuinely independent unit where residents have their own space.
- Durable Return on Investment — A well-built ADU holds its value for many years and generates both functional space and financial upside.
The ADU Construction Process Step by Step
- Initial Property Assessment and Feasibility Review — Our team visits your property to analyze zoning rules, slope conditions, and available square footage. This step tells you exactly what can be built before any resources go toward planning.
- Architectural Drafting and Space Planning — Licensed architects and designers create comprehensive blueprints based on your goals. Layouts are carefully considered to create practical, comfortable living.
- Permitting and City Approval — ADU construction in San Jose demands documentation to the city's building department for inspection and clearance. We manage this entire process on your behalf, responding to review feedback promptly.
- Ground Prep and Structural Base — Once permits are approved, on-site work kicks off. This involves leveling and prepping the ground, pouring the concrete foundation, and setting up utilities.
- Structural Framing and Weatherproofing — The structural frame is erected followed by weatherproofing and exterior finish materials. This phase, the ADU becomes recognizable as a structure.
- Interior Systems and Infrastructure — Skilled tradespeople install the heating, cooling, drainage, and power infrastructure that make the ADU fully functional. Every system is reviewed at each code checkpoint throughout ADU construction.
- Interior Finishing and Final Inspections — Trim, appliances, tile, and lighting are fitted and completed to the approved plan. A final city inspection confirms the unit is code-compliant and the unit is officially approved for use.
Who Is a Right Fit for ADU Construction?
People who see the greatest return from ADU construction generally fit within 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 common ADU construction clients, along with families navigating multigenerational living situations.
You may also be someone who runs a small business and wants a private work environment that is distinct from your family's daily life. Real estate-minded homeowners who already own residential properties are also prime candidates for ADU construction, since the return on investment is well-documented.
Situations where ADU construction may not be the best first step include properties with significant setback limitations. Very small lots or properties with easements may need a modified approach. Our team can assess each property case by case to advise you on what's feasible.
ADU Construction Common Questions Answered
How long does ADU construction typically take from start to finish?
The full timeline for ADU construction commonly spans six to fourteen months, based on the project scope and city review schedules. Permitting alone can take two to four months in San Jose, so planning ahead matters. Simpler garage conversions can move faster, while multi-room detached cottages take longer to complete.
What does ADU construction typically cost?
Budget requirements differ based on whether it's a conversion or new construction. Locally, ADU construction typically ranges from $150,000 to $400,000 or more for a standalone backyard unit. Attached website 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 formal feasibility evaluation.
Is ADU construction difficult to live through while it's underway?
How much the build affects daily life depends on whether you're converting existing space or building new. Detached backyard builds are typically less disruptive, since work happens away from the main house. Interior conversions may create short-term inconveniences during certain phases of construction. We provide advance notice about any phases that may affect your routine.
Do I need to leave my home during ADU construction?
For the majority of homeowners, you are not required to vacate your house during ADU construction. Most job sites are designed so that you remain on the property throughout the build. Exceptions may arise if significant structural connections require temporary shutoffs in ways that briefly affect habitability. Our project managers will walk you through any potential disruptions during the kickoff meeting.
How long will an ADU built through professional ADU construction last?
Any ADU built to code with professional oversight can be expected to last as long as the main residence — 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. Our builds use high-quality components 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 variety of property types that are ideally positioned for ADU construction. Homeowners in the Willow Glen neighborhood often discover their properties accommodate detached backyard units nicely. The Berryessa area have seen growing ADU activity 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.
San Jose's permitting office applies particular standards 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. Brother & Brother Builders' experience across these local conditions means fewer surprises from the first meeting to the final inspection.
Schedule Your ADU Construction Assessment Today
Should you be thinking about how to move forward with ADU construction, Brother & Brother Builders is here to help. Our experts offer proven skills in ADU construction for many different project types — from simple garage conversions to multi-room backyard residences. Every project starts with a detailed, no-pressure consultation where we listen to your goals and provide an honest assessment of what ADU construction on your property will look like.
Get in touch with our office to set up your consultation. Whether you're in the early stages of planning, our team is happy to walk through your options, review completed projects and make sure you feel confident before committing. 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