Brother & Brother Builders

Expand Your Home with Professional ADU Construction

Property owners throughout San Jose, CA are finding that adding an accessory dwelling unit is one of the most rewarding investments they can make. ADU construction opens the door to a versatile new living space on your existing property — whether you want to generate rental income. Brother & Brother Builders has guided hundreds of local homeowners see these visions to life with precision and integrity.

The popularity of ADU construction has grown rapidly in recent years, and it's not hard to see why. 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 address housing needs. If you're planning a detached backyard cottage, a garage conversion, or an attached addition, ADU construction gives you more 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 considerations, and the design choices that make an ADU truly livable. If you've been thinking about what ADU construction could look like on your property, this guide will walk you through everything you need to know.

What Is ADU Construction?

ADU construction involves 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 interior space reconfigurations.

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 city for permit approval. Once permits are secured, ADU construction moves into the physical build phase — which encompasses site preparation, framing, roofing, check here plumbing, electrical, insulation. The result is a fully functional living unit attached to or separate from your main home.

What sets quality ADU construction apart is the level of craftsmanship at every stage. Products need to be chosen to complement the existing structure. Systems like wiring and water supply must be built for long-term residential demand. Brother & Brother Builders handles every ADU construction job with the same technical discipline we bring to full custom home projects.

Key Reasons to Choose 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.
• Revenue Generation — A completed ADU is leasable as a long-term rental or short-term vacation unit, providing a consistent income stream for the homeowner.
• Space for Loved Ones — ADU construction provides adult children a private, independent living space without losing proximity to the family.
• Personalized Layouts — From two-bedroom configurations, ADU construction may be customized to your specific needs.
• Streamlined Approval Process — Recent state legislation has cut down the permitting obstacles 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 expanding urban sprawl, which aligns with sustainability goals.
• Separate Entrances and Spaces — Unlike a bedroom addition, ADU construction creates a truly separate unit where residents have their own space.
• Long-Term Investment Security — A well-built ADU continues to produce returns for decades, providing both usable housing and equity growth.

The ADU Construction Journey Step by Step

1. Site Evaluation and Zoning Analysis — Our experts review your property to analyze zoning rules, slope conditions, and available square footage. This stage clarifies exactly what's possible before any resources go toward planning.
2. Custom Design and Architectural Planning — Our design team create comprehensive blueprints based on your goals. Space is thoughtfully allocated to optimize daily use.
3. Permit Submission and Municipal Review — ADU construction in San Jose involves filing drawings to the city's building department for inspection and clearance. Brother & Brother Builders coordinates the permitting on your behalf, responding to review feedback promptly.
4. Site Preparation and Foundation Work — Once permits are issued, the build starts. This involves leveling and prepping the ground, completing foundation work, and running initial plumbing and electrical conduits.
5. Shell Construction and Exterior Finishing — The structural frame is erected followed by weatherproofing and exterior finish materials. At this stage, the ADU becomes recognizable as a structure.
6. MEP Systems Rough-In — Licensed subcontractors install the heating, cooling, drainage, and power infrastructure that make the ADU operationally complete. Every system is reviewed at each code checkpoint throughout ADU construction.
7. Interior Completion and City Sign-Off — Countertops, hardware, finishes, and fixtures are installed and finished to the agreed design. A last official inspection grants legal occupancy status 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 typically fall into a few clear categories. If you have a residential property with available square footage under zoning rules, you're already in a good starting place. Homeowners looking to generate income through rental are among the most common ADU construction clients, along with families navigating multigenerational living situations.

Another strong candidate is someone who runs a small business and wants a private work environment that is distinct from your family's daily life. Property investors and rental owners 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 properties with significant setback limitations. Sites with underground infrastructure conflicts 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 usually take from start to finish?

The complete duration for ADU construction typically ranges from six to fourteen months, depending on design complexity and city review schedules. City review on its own can take a significant portion of the overall timeline in San Jose, so starting early is important. Simpler garage conversions often finish in the lower end of the range, while multi-room detached cottages require more time.

What does ADU construction cost in San Jose?

Budget requirements differ based on the type and size of the ADU. In the San Jose area, ADU construction commonly costs $150,000 to $400,000 or more for a standalone backyard unit. Interior conversion projects tend to cost less, sometimes starting around $80,000 depending on scope. An accurate budget can only be given after completing a full site assessment.

Is ADU construction disruptive while it's underway?

The day-to-day impact depends on whether you're converting existing space or building new. Standalone ADU projects are usually easier to live alongside, since work happens away from the main house. Interior conversions may create short-term inconveniences during key milestones. Brother & Brother Builders keeps you informed about upcoming work and timelines.

Do I need to move out during ADU construction?

Generally speaking, you do not need to vacate your primary residence during ADU construction. The vast majority of projects are structured to allow you stay in your primary unit throughout the build. Certain situations could require a brief departure if interior conversion work touches shared systems in ways that briefly affect habitability. Our project managers will discuss these scenarios during the pre-construction consultation.

How long will an ADU built through professional ADU construction last?

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 commercial-grade materials and comply with all local building codes to protect your investment for the long haul.

ADU Construction for Local Homeowners

The communities throughout San Jose provide a wide range of property types that are well suited for ADU construction. Property owners near the Almaden Valley area frequently see their parcels are well configured for ADU builds. The Berryessa area are increasingly popular for ADU construction as families expand. Whether your property is near downtown San Jose, our team knows the permitting landscape well.

The City of San Jose's building department follows defined procedures for ADU construction that our team navigates routinely. Location near major arterials like Story Road or Tully Road can impact the design approach for a given ADU project. Brother & Brother Builders' experience across the San Jose permitting environment means smoother project delivery from design through the final walkthrough.

Schedule Your ADU Construction Assessment Today

When you want to move forward with ADU construction, Brother & Brother Builders is ready to guide you. Our experts offer licensed expertise in ADU construction for many different project types — from simple garage conversions to large custom detached cottages. The process begins with a thorough and honest property review where we learn what you're trying to accomplish and provide an honest assessment of what ADU construction on your property will look like.

Contact Brother & Brother Builders to schedule a site visit. Whether you're in the early stages of planning, we're glad 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 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