Brother & Brother Builders

Expand Your Home with Expert ADU Construction

Property owners throughout San Jose, CA are discovering that adding an accessory dwelling unit is one of the smartest investments they can make. ADU construction creates a versatile new living space on your existing property — whether you want to house a family member. Brother & Brother Builders has guided hundreds of local homeowners turn these plans to life with craftsmanship and transparency.

The interest in ADU construction has grown rapidly in recent years, and it's easy to understand why. California state law now makes it easier for homeowners to construct these secondary units, and local municipalities like San Jose have encouraged 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 provides increased control over how your property functions.

At Brother & Brother Builders, we apply deep hands-on experience to every ADU construction job. Our team knows the San Jose building codes, the engineering requirements, and the aesthetic decisions that make an ADU beautiful. When you're ready to explore what ADU construction could look like on your property, this guide explains everything you need to know.

What Is ADU Construction?

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 fully independent living space — including a kitchen, bathroom, sleeping area, and its own access point — 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 comprehensive review of your lot, where our professionals evaluate lot dimensions, existing structures, soil conditions, and local code requirements. From there, architectural drawings are prepared and submitted to the local building department. Once permits are secured, ADU construction enters the physical build phase — which includes foundation work, framing, roofing, plumbing, electrical, insulation. The result is a completely finished living unit connected to or independent of your main home.

What sets quality ADU construction apart is the level of craftsmanship at every stage. Products need to be chosen to match the primary home's aesthetic. Systems like wiring and water supply must be sized for independent daily use. Brother & Brother Builders handles every ADU construction job with the same professional rigor we use on major custom home projects.

Key Reasons to Choose ADU Construction

• Increased Property Value — ADU construction adds measurable 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.
• Space for Loved Ones — ADU construction offers family members a private, independent living space without losing proximity to the family.
• Design Flexibility — From open-plan one-bedrooms, ADU construction is adaptable to your specific needs.
• Simplified Regulatory Path — Recent state legislation has minimized the red tape associated with ADU construction, making the process 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 supports broader sustainability goals.
• Separate Entrances and Spaces — Unlike a bedroom addition, ADU construction creates a truly separate unit where tenants live autonomously.
• Durable Return on Investment — A well-built ADU holds its value for the long haul by offering both functional space and financial upside.

The ADU Construction Procedure Step by Step

1. Property Walkthrough and Feasibility Check — Our experts review your property to evaluate setbacks, lot coverage limits, and utility connections. This stage clarifies exactly what's possible 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 optimize daily use.
3. Permit Submission and Municipal Review — ADU construction in San Jose involves filing drawings to the city's building department for sign-off and verification. We manage this entire process on your behalf, responding to review feedback promptly.
4. Site Preparation and Foundation Work — Once permits are granted, on-site work kicks off. This covers land preparation, completing foundation work, and setting up utilities.
5. Shell Construction and Exterior Finishing — The structural frame is erected followed by insulation, sheathing, and exterior cladding. At this stage, the ADU takes its visible shape.
6. Mechanical, Electrical, and Plumbing Installation — Certified technicians install the water supply, drain lines, and electrical panel that make the ADU operationally complete. All work is inspected 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 closing municipal review confirms the unit is code-compliant and the ADU is ready for use.

Who Is a Strong Candidate for ADU Construction?

Property owners who are best suited from ADU construction generally fit within a few recognizable groups. If you own a single-family home with available square footage under zoning rules, you're already in a good starting place. Homeowners wanting to add a revenue stream through rental are among the most financially driven ADU construction clients, along with families accommodating adult children who need housing.

Another strong candidate is someone who needs a dedicated professional workspace and wants a private work environment that doesn't interfere with 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.

Those who should discuss alternatives first include lots that are below minimum size thresholds. Parcels in historic districts or HOA-restricted communities may face additional constraints. Brother & Brother Builders reviews each property on its own merits to advise you on what's feasible.

ADU Construction Frequently Asked Questions

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

The full timeline for ADU construction commonly spans six to fourteen months, influenced by the type of unit being built and how quickly approvals come through. Permitting alone can take a here significant portion of the overall timeline in San Jose, so starting early is important. Simpler garage conversions may complete more quickly, while multi-room detached cottages fall toward the upper end of the timeline.

What does ADU construction typically cost?

Pricing depends on many factors based on whether it's a conversion or new construction. Locally, ADU construction generally falls between $150,000 to $400,000 or more for a fully custom construction. Attached ADU additions often come in under, sometimes between $75,000 and $140,000. A precise cost projection can only be produced following a full site assessment.

Is ADU construction intrusive while it's underway?

How much the build affects daily life depends on the project's location on your property. Detached backyard builds are generally the least intrusive, since the crew operates at a distance from your living areas. Garage conversions or attached additions may involve some shared wall work during specific stages like framing or MEP rough-in. Our team communicates clearly about upcoming work and timelines.

Do I need to move out during ADU construction?

In most cases, you won't have to vacate your main home during ADU construction. Most job sites are designed so that you continue living in the home throughout the construction timeline. Certain situations could require a brief departure if interior conversion work touches shared systems in ways that briefly affect habitability. Our construction supervisors will discuss these scenarios during the planning phase.

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

A well-built ADU is designed to last as long as any standard residential structure — often several decades with routine maintenance. Durability depends 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 protect your investment for the long haul.

ADU Construction for San Jose Homeowners

The communities throughout San Jose provide a diverse mix of property types that are perfectly suited for ADU construction. Property owners near the Almaden Valley area have found their lots are well configured for ADU builds. Neighborhoods near Blossom Hill Road are seeing more homeowners add secondary units as housing demand rises. If you're located closer to Evergreen, our team has project experience in the area.

Local regulatory bodies in this area follows defined procedures for ADU construction that our team navigates routinely. Access to infrastructure along thoroughfares like Monterey Road can impact the design approach for a given ADU project. Our familiarity with the San Jose permitting environment 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 the team to call. Our experts offer years of hands-on experience in ADU construction for many different project types — from small attached additions to multi-room backyard residences. Our approach opens with a thorough and honest property review where we listen to your goals and give you a realistic picture of what's achievable.

Reach out to our team to begin the conversation. Even if you're just exploring the idea, we're glad to discuss timelines, costs, and design possibilities and help you take the next step. 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