Unlock New Space with Expert ADU Construction

Families in San Jose, CA are finding that adding an accessory dwelling unit is one of the most rewarding investments they can make. ADU construction creates a powerful new living space on your existing property — whether you want to generate rental income. Brother & Brother Builders has helped hundreds of local homeowners see these visions to life with skill and integrity.

The interest in ADU construction has increased significantly in recent years, and it's no mystery. California state law now makes it easier for homeowners to build these secondary units, and local municipalities like San Jose have supported the trend as a way to increase density responsibly. 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 project. Our team understands the local permitting process, the engineering requirements, and the design choices that make an ADU truly livable. Should you want to learn about what ADU construction could mean for your property, this guide covers 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 complete living space — including a kitchen, bathroom, sleeping area, and its own entrance — that is located on the same parcel as a primary residence. ADU construction includes various structural types, 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 lot dimensions, existing structures, soil conditions, and local code requirements. From there, design plans are prepared and submitted to the relevant municipal authority. Once permits are secured, 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 adjacent to or detached from your main home.

What sets quality ADU construction apart is the level of craftsmanship 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 approaches every build with the same technical discipline we apply to large-scale custom home projects.

Key Reasons to Choose ADU Construction

• Boosted Home Equity — ADU construction contributes significant market value to your property, often generating strong equity gains when it's time to sell.
• Rental Income Potential — A completed ADU may be listed as a long-term rental or short-term vacation unit, creating ongoing passive income for the homeowner.
• Space for Loved Ones — ADU construction provides adult children a self-contained residence without leaving the property.
• Personalized Layouts — From open-plan one-bedrooms, ADU construction can be tailored to the intended occupant's lifestyle.
• Streamlined Approval Process — Recent state legislation has minimized the red tape associated with ADU construction, resulting in a timeline that is faster and less expensive than ever before.
• Efficient Use of Your Lot — Building an ADU maximizes the land you already own instead of consuming open land, which supports broader sustainability goals.
• Independent Living Areas — Unlike a bedroom addition, ADU construction produces a fully self-contained unit where tenants live autonomously.
• Long-Term Investment Security — A well-built ADU continues to produce returns for decades, providing both livable square footage and monetary benefit.

The ADU Construction Journey Step by Step

1. Initial Property Assessment and Feasibility Review — Our builders assess your property to evaluate setbacks, lot coverage limits, and utility connections. This stage clarifies exactly what can be built before any resources go toward planning.
2. Custom Design and Architectural Planning — Licensed architects and designers create detailed floor plans based on your goals. Every square foot is planned to maximize function and livability.
3. Filing for Building Permits — ADU construction in San Jose demands documentation to the city's building department for review and approval. Our team handles all submissions on your behalf, resolving any revision requests promptly.
4. Excavation and Foundation Installation — Once permits are approved, the build starts. This involves leveling and prepping the ground, pouring the concrete foundation, and setting up utilities.
5. Structural Framing and Weatherproofing — Walls and roof systems go up followed by roofing, siding, windows, and exterior doors. At this stage, the ADU takes its visible shape.
6. Mechanical, Electrical, and Plumbing Installation — Licensed subcontractors install the water supply, drain lines, and electrical panel that make the ADU operationally complete. Every system is reviewed at designated stages throughout ADU construction.
7. Interior Completion and City Sign-Off — Countertops, hardware, finishes, and fixtures are fitted and completed to the agreed design. A final city inspection confirms the unit is code-compliant and the unit is officially approved for use.

Who Is a Strong Candidate for ADU Construction?

Property owners who are best suited from ADU construction often belong to a few common profiles. If you are a homeowner with a backyard, garage, or basement that could be converted, you're already well-positioned. Homeowners hoping to offset mortgage costs through rental are among the most motivated ADU construction clients, along with families navigating multigenerational living situations.

ADU construction also suits someone who works from home and wants a private work environment that doesn't interfere with your family's daily life. Real estate-minded homeowners who already own residential properties are also prime candidates for ADU construction, since the long-term value is proven.

Homeowners who may want to pause and evaluate include properties with significant setback limitations. Very small lots or properties with easements may require additional review. Our experts will evaluate each property individually and honestly to recommend the right path forward.

ADU Construction Frequently Asked Questions

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

The complete duration for ADU construction commonly spans six to fourteen months, influenced by the type of unit being built and local permitting timelines. Permitting alone can take a significant portion of the overall timeline in San Jose, so starting early is important. Smaller detached units can move faster, while multi-room detached cottages require more time.

What does ADU construction typically cost?

Budget requirements differ based on whether it's a conversion or new construction. In the San Jose area, ADU construction typically ranges from $150,000 to $400,000 or more for a standalone backyard unit. Garage conversions tend to cost less, sometimes starting around $80,000 depending on scope. A detailed estimate can only be produced following a thorough property review.

Is ADU construction disruptive while it's underway?

How much the build affects daily life depends on the project's location on your property. Detached backyard builds are typically less disruptive, since work happens away from the main house. Garage more info conversions or attached additions may require temporary access during key milestones. Our team communicates clearly about upcoming work and timelines.

Do I need to leave my home during ADU construction?

In most cases, you are not required to vacate your main home during ADU construction. Most builds are set up to let you remain on the property throughout the process. 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 planning phase.

How long will an ADU built through professional ADU construction remain in good condition?

An ADU constructed with quality materials is designed to last as long as the main residence — often several decades with routine maintenance. Longevity is tied to the quality of materials used, whether the unit is properly cared for, and whether systems like roofing and plumbing are serviced regularly. Our builds use residential-grade products rated for longevity 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 wide range of property types that are well 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 housing demand rises. If you're located closer to Evergreen, our team knows the permitting landscape well.

The City of San Jose's building department applies particular standards for ADU construction that our team navigates routinely. Proximity to transit corridors can influence utility connection requirements for a given ADU project. Our familiarity with these local conditions means smoother project delivery from the first meeting to the final inspection.

Schedule Your ADU Construction Assessment Today

When you want to move forward with ADU construction, Brother & Brother Builders is here to help. We bring licensed expertise in ADU construction including all types of project types — from simple garage conversions to multi-room backyard residences. The process begins with a detailed, no-pressure consultation 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 schedule a site visit. No matter where you are in the decision-making process, our team is happy to 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