Expand Your Home with Expert ADU Construction
Families in San Jose, CA are realizing 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 supported hundreds of local homeowners turn these plans to life with craftsmanship and integrity.
The popularity of ADU construction has increased significantly 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 embraced 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 offers greater control over how your property works.
At Brother & Brother Builders, we draw on extensive hands-on experience to every ADU construction build. Our team knows the San Jose building codes, the engineering requirements, and the aesthetic decisions that make an ADU beautiful. Should you want to learn about what ADU construction could do for your property, this guide explains everything you need to know.
What Is an ADU Build?
ADU construction describes the process of planning, approving, and constructing 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 entryway — that sits on the same property as a primary residence. ADU construction can take several forms, 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 lot dimensions, existing structures, soil conditions, and local code requirements. From there, architectural drawings are prepared and submitted to the relevant municipal authority. Once approvals are in place, ADU construction moves into the physical build phase — which includes foundation work, framing, mechanical systems, weatherproofing, and interior finishing. The result is a completely finished 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 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
- Boosted Home Equity — ADU construction adds measurable market value to your property, often returning more than the build cost when it's time to sell.
- Rental Income Potential — 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 self-contained residence without leaving the property.
- Design Flexibility — From two-bedroom configurations, ADU construction is adaptable to the intended occupant's lifestyle.
- Simplified Regulatory Path — Recent state legislation has reduced the red tape associated with ADU construction, resulting in a timeline that is faster and more affordable than ever before.
- Responsible Property Development — Building an ADU works within your current footprint instead of expanding urban sprawl, which contributes to sustainability goals.
- Independent Living Areas — Unlike a bedroom addition, ADU construction produces a fully self-contained unit where tenants live autonomously.
- Durable Return on Investment — A well-built ADU continues to produce returns for decades, providing both usable housing and equity growth.
The ADU Construction Procedure Step by Step
- Property Walkthrough and Feasibility Check — Our experts review your property to analyze zoning rules, slope conditions, and available square footage. This step tells you exactly what can be built before any time is invested in drawings.
- Blueprint Development and Layout Design — Experienced draftspeople create precise architectural drawings reflecting your priorities. Space is thoughtfully allocated 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. Our team handles all submissions on your behalf, responding to review feedback promptly.
- Excavation and Foundation Installation — Once permits are approved, physical construction begins. This includes grading the site, completing foundation work, and setting up utilities.
- Structural Framing and Weatherproofing — Framing is completed followed by weatherproofing and exterior finish materials. During this step, the ADU becomes recognizable as a structure.
- Interior Systems and Infrastructure — Licensed subcontractors install the water supply, drain lines, and electrical panel that make the ADU fully functional. All work is inspected at required milestones throughout ADU construction.
- Interior Finishing and Final Inspections — Countertops, hardware, finishes, and fixtures are placed and inspected to the agreed design. A closing municipal review confirms the unit is code-compliant 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 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 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.
Another strong candidate is someone who needs a dedicated professional workspace and wants a separate office or studio space that doesn't interfere with 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 return on investment is well-documented.
Situations where ADU construction may not be the best first step include lots that are below minimum size thresholds. Very small lots or properties with easements may face additional constraints. Our team can assess each property on its own merits to provide realistic options.
ADU Construction Common Questions Answered
How long does ADU construction usually take from start to finish?
The full timeline for ADU construction commonly spans six to fourteen months, depending on design complexity and local permitting timelines. 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. Smaller detached units may complete more quickly, while multi-room detached cottages fall toward the upper end of the timeline.
What does ADU construction typically cost?
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 fully custom construction. Garage conversions tend to cost less, sometimes starting around $80,000 depending on scope. An accurate budget can only be produced following a full site assessment.
Is ADU construction intrusive while it's underway?
The day-to-day impact depends on where the ADU is being built. Detached backyard builds are typically less disruptive, since work happens away from the main house. Interior conversions may involve some shared wall work during key milestones. Our team communicates clearly about what to expect at each stage.
Do I need to move out during ADU construction?
Generally speaking, you are not required to vacate your primary residence during ADU construction. Most job sites are structured to allow you continue living in the home throughout the construction timeline. website Exceptions may arise if interior conversion work touches shared systems in ways that temporarily impact livability. Our project managers will flag these situations during the pre-construction consultation.
How long will an ADU built through professional ADU construction last?
A well-built ADU is designed to last as long as your primary home — often several decades with routine maintenance. Longevity is tied to the standard of construction, how well routine maintenance is performed, and whether systems like roofing and plumbing are serviced regularly. Our builds use commercial-grade materials 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 variety of property types that are perfectly suited for ADU construction. Property owners near the Almaden Valley area frequently see their parcels work well for both attached and detached projects. The Berryessa area are seeing more homeowners add secondary units as multigenerational living becomes more common. Whether your property is near downtown San Jose, our team has likely worked nearby.
The City of San Jose's building department 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. Our team's knowledge of the San Jose permitting environment means more accurate timelines and budgets from the first meeting to the final inspection.
Book Your ADU Construction Consultation Today
When you want to move forward with ADU construction, Brother & Brother Builders is the team to call. Our builders provide proven skills in ADU construction across a wide range of project types — from small attached additions to large custom detached cottages. The process begins 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.
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 give you the clarity you need to move forward. 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