Brother & Brother Builders

Expand Your Home with Professional ADU Construction

Homeowners across San Jose, CA are finding that adding an accessory dwelling unit is one of the most practical investments they can make. ADU construction provides a flexible new living space on your existing property — whether you want to generate rental income. Brother & Brother Builders has helped hundreds of local homeowners turn these plans to life with precision and integrity.

The interest in ADU construction has surged in recent years, and it's easy to understand why. California state law now makes it easier for homeowners to add these secondary units, and local municipalities like San Jose have encouraged the trend as a way to expand the housing supply. Whether you're building 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 bring years of hands-on experience to every ADU construction build. Our team is familiar with city and county requirements, the engineering considerations, and the aesthetic decisions that make an ADU truly livable. Should you want to learn about what ADU construction could do for your property, this guide explains everything you need to know.

What Is an ADU Build?

ADU construction refers to the process of planning, approving, and constructing 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 entryway — that exists on the same lot as a primary residence. ADU construction includes various structural types, including detached backyard units, attached additions, garage conversions, and even basement or interior conversions.

Mechanically, everything kicks off with a thorough property evaluation, where our team evaluate lot dimensions, existing structures, soil conditions, and local code requirements. From there, design plans are prepared and submitted to the local building department. Once the paperwork is cleared, ADU construction moves into the physical build phase — which encompasses site preparation, framing, mechanical systems, weatherproofing, and interior finishing. The result is a move-in-ready living unit adjacent to or detached from your main home.

What separates excellent ADU construction from an average project is the attention to detail at every stage. Materials must be selected to complement the existing structure. Systems like wiring and water supply must be sized for independent daily use. Brother & Brother Builders treats each project with the same professional rigor we apply to large-scale custom home projects.

Key Advantages ADU Construction

• Boosted Home Equity — ADU construction delivers real market value to your property, often generating strong equity gains when it's time to sell.
• Monthly Cash Flow — A completed ADU may be listed as a long-term rental or short-term vacation unit, providing a consistent income stream for the homeowner.
• Multi-Generational Living — ADU construction offers family members a self-contained residence without moving to another neighborhood.
• Design Flexibility — From modern studio layouts, ADU construction may be customized to your specific needs.
• Faster Permitting in California — Recent state legislation has minimized 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 requiring new development, which aligns with sustainability goals.
• Separate Entrances and Spaces — Unlike a bedroom addition, ADU construction delivers a genuinely independent unit where occupants have full privacy.
• Durable Return on Investment — A well-built ADU remains an asset for many years and generates both usable housing and equity growth.

The ADU Construction Journey Step by Step

1. Property Walkthrough and Feasibility Check — Our team visits your property to analyze zoning rules, slope conditions, and available square footage. This phase answers exactly what's possible before any time is invested in drawings.
2. Custom Design and Architectural Planning — Our design team create precise architectural drawings tailored to your needs. Space is thoughtfully allocated to maximize function and livability.
3. Filing for Building Permits — ADU construction in San Jose involves filing drawings 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. Excavation and Foundation Installation — Once permits are issued, physical construction begins. This involves leveling and prepping the ground, laying the structural base, and establishing utility connections.
5. Shell Construction and Exterior Finishing — Framing is completed followed by weatherproofing and exterior finish materials. During this step, the ADU becomes recognizable as a structure.
6. MEP Systems Rough-In — Certified technicians install the heating, cooling, drainage, and power infrastructure that make the ADU operationally complete. All work is inspected at each code checkpoint throughout ADU construction.
7. Finishes, Fixtures, and Final Walkthrough — 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 Right Fit for ADU Construction?

Property owners who are best suited from ADU construction often belong to a few clear categories. If you are a homeowner with enough lot space to meet setback requirements, you're already in a good starting place. Homeowners hoping to offset mortgage costs through rental are among the most common ADU construction clients, along with families navigating multigenerational living situations.

ADU construction also suits someone who needs a dedicated professional workspace and wants a private work environment that doesn't interfere with your family's daily life. Property investors and rental owners 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. Very small lots or properties with easements may face additional constraints. Brother & Brother Builders reviews each property on its own merits to recommend the right path forward.

ADU Construction Common Questions Answered

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. The approval phase alone can take several months in San Jose, so starting early is important. Straightforward interior conversions often finish in the lower end of the range, while custom detached builds take longer to complete.

What does ADU construction cost in San Jose?

Budget requirements differ based on whether it's a conversion or new construction. For most projects in here this region, ADU construction commonly costs $150,000 to $400,000 or more for a detached new build. Garage conversions often come in under, sometimes in the $80,000 to $150,000 range. A detailed estimate can only be produced following a thorough property review.

Is ADU construction disruptive while it's underway?

The level of disruption depends on where the ADU is being built. Detached backyard builds are generally the least intrusive, since the crew operates at a distance from your living areas. Projects that connect to the main structure may create short-term inconveniences during specific stages like framing or MEP rough-in. We provide advance notice about upcoming work and timelines.

Do I need to leave my home during ADU construction?

For the majority of homeowners, you do not need to vacate your house during ADU construction. The vast majority of projects are structured to allow you continue living in the home throughout the process. There are edge cases if significant structural connections require temporary shutoffs in ways that temporarily impact livability. Our project managers will walk you through any potential disruptions during the planning phase.

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 — typically 50 years or more. Durability depends to the quality of materials used, how consistently minor repairs are addressed, 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 ensure lasting performance.

ADU Construction for San Jose Homeowners

Residential areas across San Jose present a wide range of property types that are ideally positioned for ADU construction. Residents in the Rose Garden district often discover their properties accommodate detached backyard units nicely. Neighborhoods near Blossom Hill Road are increasingly popular for ADU construction as families expand. Whether your property is near downtown San Jose, our team has project experience in the area.

San Jose's permitting office follows defined procedures for ADU construction that require a builder familiar with local expectations. Proximity to transit corridors can impact the design approach for a given ADU project. Our team's knowledge of this region's building landscape means fewer surprises from the first meeting to the final inspection.

Start Your ADU Construction Planning Session Today

When you want to add an ADU to your property, Brother & Brother Builders is here to help. Our builders provide licensed expertise in ADU construction including all types of project types — from simple garage conversions to fully independent secondary homes. The process begins with a detailed, no-pressure consultation where we listen to your goals and share clear expectations of what ADU construction on your property will look like.

Contact Brother & Brother Builders to begin the conversation. No matter where you are in the decision-making process, we're glad to 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