Expand Your Home with Expert ADU Construction

Families in San Jose, CA are realizing 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 helped hundreds of local homeowners bring these projects to life with precision and care.

The interest in ADU construction has increased significantly in recent years, and it's easy to understand why. California state law has streamlined permitting 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 serves your household.

At Brother & Brother Builders, we apply deep hands-on experience to every ADU construction build. Our team understands the local permitting process, the engineering details, and the planning steps that make an ADU truly livable. When you're ready to explore 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 describes 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 — equipped with 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 thorough property evaluation, where our professionals evaluate property boundaries, available square footage, and infrastructure capacity. From there, architectural drawings are prepared and submitted to the local building department. Once approvals are in place, ADU construction enters the physical build phase — which includes foundation work, framing, HVAC, drywall, flooring, and exterior finishes. The result is a fully functional living unit attached to or separate from your main home.

What sets quality ADU construction apart is the attention to detail at every stage. Products need to be chosen to align with the neighborhood's character. Systems like HVAC and drainage must be built for long-term residential demand. Brother & Brother Builders approaches every build with the same high standards we bring to full custom home projects.

Key Advantages ADU Construction

• Higher Resale Potential — ADU construction delivers real market value to your property, often generating strong equity gains when it's time to sell.
• Revenue Generation — A completed ADU is leasable as a long-term rental or short-term vacation unit, creating ongoing passive income for the homeowner.
• Multi-Generational Living — ADU construction offers family members a comfortable home of their own without leaving the property.
• Design Flexibility — From open-plan one-bedrooms, ADU construction is adaptable to the intended occupant's lifestyle.
• Faster Permitting in California — 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.
• Responsible Property Development — Building an ADU uses your existing lot instead of requiring new development, which supports broader sustainability goals.
• Privacy for All Residents — Unlike a bedroom addition, ADU construction produces a fully self-contained unit where occupants have full privacy.
• Long-Term Investment Security — A well-built ADU continues to produce returns for decades, providing both functional space and financial upside.

The ADU Construction Procedure Step by Step

1. Site Evaluation and Zoning Analysis — Our builders assess your property to evaluate setbacks, lot coverage limits, and utility connections. This phase answers exactly what ADU types will work before any money is spent on design.
2. Architectural Drafting and Space Planning — Our design team create detailed floor plans reflecting your priorities. Space is thoughtfully allocated to maximize function and livability.
3. Filing for Building Permits — ADU construction in San Jose requires submitting plans to the city's building department for review and approval. Our team handles all submissions on your behalf, responding to review feedback promptly.
4. Excavation and Foundation Installation — Once permits are issued, the build starts. This involves leveling and prepping the ground, pouring the concrete foundation, and establishing utility connections.
5. Framing, Roofing, and Exterior Work — The structural frame is erected followed by insulation, sheathing, and exterior cladding. This phase, the ADU transforms from a concept to a building.
6. Mechanical, Electrical, and Plumbing Installation — Skilled tradespeople install the water supply, drain lines, and electrical panel that make the ADU operationally complete. All work is inspected at required milestones throughout ADU construction.
7. Finishes, Fixtures, and Final Walkthrough — Trim, appliances, tile, and lighting are fitted and completed to the approved plan. A last official inspection confirms the unit is code-compliant and the unit is officially approved for use.

Who Is a Right Fit for ADU Construction?

Homeowners who benefit most from ADU construction typically fall into a few recognizable groups. If you are a homeowner with enough lot space to meet setback requirements, you're already well-positioned. Homeowners looking to generate income through rental are among the most financially driven ADU construction clients, along with families navigating multigenerational living situations.

You may also be someone who runs a small business and wants a detached creative or business space that remains away from your family's daily life. Landlords and real estate investors who already own residential properties 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 lots that are below minimum size thresholds. Sites with underground infrastructure conflicts may require additional review. 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 total process for ADU construction usually runs between six to fourteen months, influenced by the type of unit being built and city review schedules. Permitting alone can take several months in San Jose, so beginning the process sooner rather than later is wise. Simpler garage conversions often finish in the lower end of the range, while multi-room detached cottages take longer to complete.

What does ADU construction typically cost?

Costs vary widely based on the type and size of the ADU. For most projects in this region, ADU construction typically get more info ranges from $150,000 to $400,000 or more for a detached new build. Garage conversions tend to cost less, sometimes in the $80,000 to $150,000 range. A detailed estimate can only be given after completing a thorough property review.

Is ADU construction difficult to live through while it's underway?

The level of disruption depends on where the ADU is being built. Detached backyard builds are usually easier to live alongside, since the crew operates at a distance from your living areas. Projects that connect to the main structure may require temporary access during key milestones. We provide advance notice about any phases that may affect your routine.

Do I need to leave my home during ADU construction?

Generally speaking, you do not need to vacate your house during ADU construction. Most job sites are set up to let you continue living in the home throughout the construction timeline. There are edge cases if significant structural connections require temporary shutoffs in ways that briefly affect habitability. Our project managers will flag these situations during the kickoff meeting.

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 — indefinitely with proper upkeep. How long it lasts comes down to the quality of materials used, how well routine maintenance is performed, and if mechanical components are maintained on schedule. We select high-quality components and build to current California residential standards to ensure lasting performance.

ADU Construction for Local Homeowners

Residential areas across San Jose present a variety of property types that are perfectly suited for ADU construction. Property owners near the Almaden Valley area have found their lots accommodate detached backyard units nicely. Neighborhoods near Blossom Hill Road are increasingly popular for ADU construction as multigenerational living becomes more common. Whether your property is near downtown San Jose, our team has project experience in the area.

Local regulatory bodies in this area has developed specific protocols for ADU construction that our team navigates routinely. Access to infrastructure along thoroughfares like Monterey Road can influence utility connection requirements for a given ADU project. Brother & Brother Builders' experience across this region's building landscape means fewer surprises from design through the final walkthrough.

Start Your ADU Construction Planning Session Today

If you're ready to add an ADU to your property, Brother & Brother Builders is ready to guide you. We bring years of hands-on experience in ADU construction for many different project types — from modest studio builds to fully independent secondary homes. The process begins with a comprehensive site assessment where we learn what you're trying to accomplish and give you a realistic picture of what's achievable.

Get in touch with our office to begin the conversation. Even if you're just exploring the idea, our team is happy to answer questions, share examples of our work and help you take the next step. Building an ADU is a major decision — 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