Expand Your Home with Expert 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 helped hundreds of local homeowners turn these plans to life with skill and transparency.

The interest in ADU construction has increased significantly in recent years, and it's easy to understand why. California state law has simplified the process for homeowners to build these secondary units, and local municipalities like San Jose have supported the trend as a way to address housing needs. Whether you want to build a detached backyard cottage, a garage conversion, or an attached addition, ADU construction gives you more control over how your property serves your household.

At Brother & Brother Builders, we bring years of hands-on experience to every ADU construction job. Our team knows the San Jose building codes, the engineering requirements, and the design choices that make an ADU beautiful. Should you want to learn about what ADU construction could do for your property, this guide will walk you through everything you need to know.

What Is ADU Construction?

ADU construction describes 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 — equipped with a kitchen, bathroom, sleeping area, and its own entrance — 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, everything kicks off with a comprehensive review of your lot, where our builders 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 transitions to the physical build phase — which includes foundation work, framing, mechanical systems, weatherproofing, and interior finishing. The result is a completely finished living unit attached to or separate from 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 complement the existing structure. Systems like plumbing and electrical must be built for long-term residential demand. Brother & Brother Builders treats each project with the same technical discipline we apply to large-scale custom home projects.

Key Reasons to Choose 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.
• 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 provides adult children a comfortable home of their own without leaving the property.
• Design Flexibility — From open-plan one-bedrooms, ADU construction may be customized to your specific needs.
• Faster Permitting in California — Recent state legislation has cut down the barriers and delays associated with ADU construction, creating a path that is faster and less expensive than ever before.
• Responsible Property Development — Building an ADU maximizes the land you already own instead of consuming open land, which contributes to sustainability goals.
• Separate Entrances and Spaces — Unlike a bedroom addition, ADU construction delivers a genuinely independent unit where tenants live autonomously.
• Lasting Financial Benefit — A well-built ADU holds its value for decades, providing both usable housing and equity growth.

The ADU Construction Journey Step by Step

1. Site Evaluation and Zoning Analysis — Our team visits your property to determine what type of ADU is allowed and where it can be placed. This step tells you exactly what's possible before any resources go toward planning.
2. Architectural Drafting and Space Planning — Our design team create comprehensive blueprints based on your goals. Every square foot is planned to create practical, comfortable living.
3. Permitting and City Approval — 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, addressing any city comments promptly.
4. Ground Prep and Structural Base — Once permits are granted, on-site work kicks off. This covers land preparation, completing foundation work, and establishing utility connections.
5. Framing, Roofing, and Exterior Work — Framing is completed followed by roofing, siding, windows, and exterior doors. This phase, the ADU takes its visible shape.
6. Interior Systems and Infrastructure — Skilled tradespeople install the water supply, drain lines, and electrical panel that make the ADU operationally complete. Inspections are completed at designated stages throughout ADU construction.
7. Interior Completion and City Sign-Off — Flooring, cabinetry, fixtures, paint are placed and inspected to your specifications. A last official inspection issues the certificate of occupancy and the unit is officially approved for use.

Who Is a Good Candidate for ADU Construction?

Property owners who are best suited from ADU construction typically fall into a few clear categories. If you have a residential property with enough lot space to meet setback requirements, you're already a strong candidate. Homeowners wanting to add a revenue stream 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 private work environment that remains away from your family's daily life. Landlords and real estate investors who are building a portfolio are also well suited for ADU construction, since the long-term value is proven.

Those who should discuss alternatives first include properties with significant setback limitations. Very small lots or properties with easements may require additional review. Our experts will evaluate each property on its own merits to advise you on what's feasible.

ADU Construction FAQ

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

The complete duration for ADU construction commonly spans six to fourteen months, based on the project scope and local permitting timelines. City review on its own can take several months in San Jose, so beginning the process sooner rather than later is wise. Smaller detached units may complete more quickly, while custom detached builds require more time.

What does ADU construction typically cost?

Costs vary widely 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 detached new build. Garage conversions tend to cost less, sometimes between $75,000 and $140,000. A precise cost projection can only be developed after a thorough property review.

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

The day-to-day impact depends on whether you're converting existing space or building new. Standalone ADU projects are typically less disruptive, since work happens away from the main house. Interior conversions may involve some shared wall work during specific stages like framing or MEP rough-in. We provide advance notice about what to expect at each stage.

Do I need to leave my home during ADU construction?

For the majority of homeowners, you are not required to vacate your primary residence during ADU construction. The vast majority of projects are structured to allow you remain on the property throughout the construction timeline. Exceptions may arise if interior conversion work touches shared systems in ways that briefly affect habitability. Our construction supervisors will walk you through any potential disruptions during the pre-construction consultation.

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

A well-built ADU is designed to last as long as any standard residential structure — typically 50 years or more. Longevity is tied to the quality of materials used, whether the unit is properly cared for, and how proactively issues are resolved over time. Brother & Brother Builders specifies residential-grade products rated for longevity and build to current California residential standards to ensure lasting performance.

ADU Construction for San Jose Homeowners

San Jose's neighborhoods offer a wide range of property types that are perfectly suited for ADU construction. Homeowners in the Willow Glen neighborhood frequently see their parcels work well for both attached and detached projects. Neighborhoods near Blossom Hill Road are increasingly popular for ADU construction as families expand. If you're located closer to Evergreen, our team has likely worked nearby.

Local get more info regulatory bodies in this area follows defined procedures for ADU construction that experienced builders know well. 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 smoother project delivery from design through the final walkthrough.

Start Your ADU Construction Assessment 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 builders provide years of hands-on experience in ADU construction for many different project types — from modest studio builds to multi-room backyard residences. The process begins with a thorough and honest property review where we learn what you're trying to accomplish and give you a realistic picture of what's achievable.

Reach out to our team to begin the conversation. No matter where you are in the decision-making process, we enjoy walk through your options, review completed projects 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