Brother & Brother Builders

Unlock New Space with Expert ADU Construction

Families in San Jose, CA are realizing that adding an accessory dwelling unit is one of the most practical 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 guided hundreds of local homeowners turn these plans to life with craftsmanship and integrity.

The interest in ADU construction has increased significantly in recent years, and it's no mystery. California state law has streamlined permitting for homeowners to add these secondary units, and local municipalities like San Jose have encouraged 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 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 details, and the design choices that make an ADU truly livable. If you've been thinking about what ADU construction could do for your property, this guide explains everything you need to know.

What Is the ADU Construction Process?

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 access point — that sits on the same property as a primary residence. ADU construction can take several forms, including detached backyard units, attached additions, garage conversions, and even interior space reconfigurations.

Mechanically, the work starts with a detailed site assessment, where our team evaluate lot dimensions, existing structures, soil conditions, and local code requirements. From there, design plans are prepared and submitted to the city for permit approval. Once permits are secured, ADU construction transitions to the physical build phase — which covers everything from foundational work, framing, roofing, plumbing, electrical, insulation. The result is a fully functional living unit adjacent to or detached from your main home.

What sets quality ADU construction apart is the depth of planning at every stage. Materials must be selected to align with the neighborhood's character. Systems like wiring and water supply must be built for long-term residential demand. Brother & Brother Builders approaches every build with the same professional rigor we use on major custom home projects.

Key Benefits 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 is leasable as a long-term rental or short-term vacation unit, creating ongoing passive income for the homeowner.
• Multi-Generational Living — ADU construction gives aging parents a self-contained residence without losing proximity to the family.
• Personalized Layouts — From open-plan one-bedrooms, ADU construction is adaptable to your specific needs.
• Simplified Regulatory Path — Recent state legislation has cut down the red tape associated with ADU construction, making the process that is faster and less expensive than ever before.
• Sustainable Land Use — Building an ADU uses your existing lot instead of expanding urban sprawl, which contributes to sustainability goals.
• Independent Living Areas — Unlike a bedroom addition, ADU construction produces a fully self-contained unit where residents have their own space.
• Durable Return on Investment — A well-built ADU remains an asset for many years and generates both livable square footage and monetary benefit.

The ADU Construction Journey Step by Step

1. Site Evaluation and Zoning Analysis — Our experts review your property to evaluate setbacks, lot coverage limits, and utility connections. This step tells you exactly what can be built before any money is spent on design.
2. Blueprint Development and Layout Design — Experienced draftspeople create precise architectural drawings tailored to your needs. Every square foot is planned to optimize daily use.
3. Permit Submission and Municipal Review — ADU construction in San Jose requires submitting plans to the city's building department for sign-off and verification. Brother & Brother Builders coordinates the permitting on your behalf, addressing any city comments promptly.
4. Ground Prep and Structural Base — Once permits are approved, physical construction begins. This involves leveling and prepping the ground, completing foundation work, and establishing utility connections.
5. Framing, Roofing, and Exterior Work — Walls and roof systems go up followed by weatherproofing and exterior finish materials. During this step, the ADU takes its visible shape.
6. Interior Systems and Infrastructure — Skilled tradespeople install the heating, cooling, drainage, and power infrastructure that make the ADU fully functional. Every system is reviewed at designated stages throughout ADU construction.
7. Interior Finishing and Final Inspections — Trim, appliances, tile, and lighting are installed and finished to the approved plan. A closing municipal review confirms the unit is code-compliant 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 generally fit within a few recognizable groups. If you are a homeowner with a backyard, garage, or basement that could be converted, you're already well-positioned. Homeowners wanting to add a revenue stream through rental are among the most motivated ADU construction clients, along with families accommodating adult children who need housing.

Another strong candidate is someone who runs a small business and wants a separate office or studio space that remains away from your family's daily life. Landlords and real estate investors who already own residential properties are also well suited for ADU construction, since the return on investment is well-documented.

Those who should discuss alternatives first include sites with unusual utility access challenges. Very small lots or properties with easements may face additional constraints. Our team can assess each property on its own merits to recommend the right path forward.

ADU Construction Common Questions Answered

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

The total process for ADU construction commonly spans six to fourteen months, depending on design complexity and local permitting timelines. Permitting alone can take several months in San Jose, so beginning the process sooner rather than later is wise. Smaller detached units often finish in the lower end of the range, while custom detached builds take longer to complete.

What does ADU construction typically cost?

Budget requirements differ based on the type here 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. Attached ADU additions 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 difficult to live through while it's underway?

The day-to-day impact depends on the project's location on your property. New construction in the rear yard are generally the least intrusive, since the crew operates at a distance from your living areas. Garage conversions or attached additions may create short-term inconveniences during certain phases of construction. Brother & Brother Builders keeps you informed about upcoming work and timelines.

Do I need to vacate the property during ADU construction?

Generally speaking, you are not required to vacate your primary residence during ADU construction. Most builds are designed so that you continue living in the home throughout the build. Exceptions may arise if major utility upgrades affect the main house in ways that temporarily impact livability. Our project managers will discuss these scenarios during the planning phase.

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

An ADU constructed with quality materials should last as long as any standard residential structure — often several decades with routine maintenance. Longevity is tied to the systems installed, how well routine maintenance is performed, and how proactively issues are resolved over time. Our builds use high-quality components and comply with all local building codes 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. Communities around the Capitol Expressway corridor have seen growing ADU activity as families expand. If you're located closer to Evergreen, our team knows the permitting landscape well.

San Jose's permitting office applies particular standards for ADU construction that our team navigates routinely. Location near major arterials like Story Road or Tully Road can influence utility connection requirements for a given ADU project. Our familiarity with these local conditions means more accurate timelines and budgets from the first meeting to the final inspection.

Start Your ADU Construction Consultation Today

If you're ready to add an ADU to your property, Brother & Brother Builders is here to help. We bring licensed expertise in ADU construction across a wide range of project types — from simple garage conversions to large custom detached cottages. Every project starts with a thorough and honest property review where we learn what you're trying to accomplish and share clear expectations of what the project will involve.

Get in touch with our office to schedule a site visit. Whether you're in the early stages of planning, our team is happy to answer questions, share examples of our work 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