Expand Your Home with Professional ADU Construction

Families in San Jose, CA are finding that adding an accessory dwelling unit is one of the smartest investments they can make. ADU construction creates a powerful 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 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 embraced 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 offers greater control over how your property functions.

At Brother & Brother Builders, we bring years of hands-on experience to every ADU construction build. Our team is familiar with city and county requirements, the engineering details, and the planning steps that make an ADU functional. Should you want to learn about what ADU construction could look like on your property, this guide will walk you through everything you need to know.

What Is the ADU Construction Process?

ADU construction refers to the process of designing, permitting, and building an accessory dwelling unit on a residential property. An accessory dwelling unit is a complete living space — featuring a kitchen, bathroom, sleeping area, and its own entryway — 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 below-grade dwelling units.

Mechanically, the work starts with a detailed site assessment, where our professionals evaluate setbacks, zoning, utility access, and structural feasibility. From there, blueprints are prepared and submitted to the local building department. Once approvals are in place, ADU construction enters the physical build phase — which encompasses site preparation, framing, mechanical systems, weatherproofing, and interior finishing. The result is a fully functional living unit connected to or independent of your main home.

What separates excellent ADU construction from an average project is the depth of planning at every stage. Materials must be selected to align with the neighborhood's character. Systems like plumbing and electrical must be built for long-term residential demand. Brother & Brother Builders approaches every build with the same professional rigor we bring to full custom home projects.

Key Benefits ADU Construction

• Increased Property Value — ADU construction contributes significant market value to your property, often returning more than the build cost when it's time to sell.
• Rental Income Potential — A completed ADU is leasable as a long-term rental or short-term vacation unit, providing a consistent income stream for the homeowner.
• Multi-Generational Living — ADU construction gives aging parents a self-contained residence without moving to another neighborhood.
• Personalized Layouts — From two-bedroom configurations, ADU construction may be customized to your specific needs.
• Simplified Regulatory Path — Recent state legislation has cut down the permitting obstacles associated with ADU construction, making the process that is faster and more cost-efficient than ever before.
• Efficient Use of Your Lot — Building an ADU maximizes the land you already own instead of requiring new development, which supports broader sustainability goals.
• Separate Entrances and Spaces — Unlike a bedroom addition, ADU construction creates a truly separate unit where tenants live autonomously.
• Durable Return on Investment — A well-built ADU holds its value for the long haul by offering both functional space and financial upside.

The ADU Construction Journey Step by Step

1. Property Walkthrough and Feasibility Check — Our experts review your property to evaluate setbacks, lot coverage limits, and utility connections. This stage clarifies exactly what's possible before any time is invested in drawings.
2. Custom Design and Architectural Planning — Our design team create detailed floor plans reflecting your priorities. Layouts are carefully considered to create practical, comfortable living.
3. Filing for Building Permits — ADU construction in San Jose demands documentation to the city's building department for review and approval. Brother & Brother Builders coordinates the permitting on your behalf, addressing any city comments promptly.
4. Site Preparation and Foundation Work — Once permits are granted, the build starts. This involves leveling and prepping the ground, completing foundation work, and establishing utility connections.
5. Shell Construction and Exterior Finishing — Walls and roof systems go up followed by insulation, sheathing, and exterior cladding. During this step, the ADU transforms from a concept to a building.
6. Interior Systems and Infrastructure — Licensed subcontractors install the plumbing lines, electrical wiring, and HVAC systems that make the ADU operationally complete. Inspections are completed at designated stages throughout ADU construction.
7. Interior Finishing and Final Inspections — Trim, appliances, tile, and lighting are fitted and completed to your specifications. A closing municipal review grants legal occupancy status 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 clear categories. If you are a homeowner with available square footage under zoning rules, you're already in a good starting place. Homeowners wanting to add a revenue stream through rental are among the most financially driven ADU construction clients, along with families accommodating adult children who need housing.

Another strong candidate is someone who works from home and wants a separate office or studio space that is distinct from your family's daily life. Property investors and rental owners 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 need a modified approach. Our experts will evaluate each property on its own merits to recommend the right path forward.

ADU Construction Frequently Asked Questions

How long does ADU construction generally take from start to finish?

The full timeline for ADU construction usually runs between six to fourteen months, based on the project scope and local permitting timelines. City review on its own 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 often finish in the lower end of the range, while multi-room detached cottages take longer to complete.

What does ADU construction cost in San Jose?

Costs vary widely based on project complexity and finishes selected. In the San Jose area, ADU construction typically ranges from $150,000 to $400,000 or more for a standalone backyard unit. Interior conversion projects tend to cost less, sometimes in the $80,000 to $150,000 range. An accurate budget can only be developed after a full site assessment.

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. New construction in the rear yard are generally the least intrusive, since the crew operates at a distance from your living areas. Interior conversions may involve some shared wall work during key milestones. Our team communicates clearly about any phases that may affect your routine.

Do I need to vacate the property during ADU construction?

For the majority of homeowners, you are not required to vacate your house during ADU construction. Most job sites are set up to let you stay in your primary unit throughout the build. Exceptions may arise if significant structural connections require temporary shutoffs in ways that briefly affect habitability. Our construction supervisors will flag these situations during the pre-construction consultation.

How long will an ADU built through professional ADU construction hold up?

Any ADU built to code with professional oversight is designed to last as long as the main residence — typically 50 years or more. How long it lasts comes down to the quality of materials used, whether the unit is properly cared for, and if mechanical components are maintained on schedule. Our builds use residential-grade products rated for longevity and build to current California residential standards to deliver a structure that stands the test of time.

ADU Construction for San Jose Homeowners

Residential areas across San Jose present a variety of property types that are perfectly suited for ADU construction. Residents in the Rose Garden district often discover their properties work well for both attached and detached projects. 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 project experience in the area.

Local regulatory bodies in this area has developed specific protocols for ADU construction that require a builder familiar with local expectations. Proximity to transit corridors can affect how quickly permits are approved for a given ADU project. Brother & Brother Builders' experience across these local conditions means smoother project delivery from design through the final walkthrough.

Book Your ADU Construction Consultation Today

If you're ready to explore what an ADU could look like on your lot, Brother & Brother Builders is ready to guide you. Our experts offer licensed expertise in ADU construction across a wide range of project types — from simple garage conversions to multi-room backyard residences. The process begins with a comprehensive site assessment where we listen to your goals and give you a realistic picture of what's achievable.

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 answer questions, share examples of our work and make sure you feel confident before committing. This type of project is a meaningful commitment — and our goal is to here ensure it delivers real value.

Brother & Brother Builders | 3109 Stevens Creek Boulevard | San Jose CA 95117 | (888) 412-2632