Brother & Brother Builders

Expand Your Home with Professional ADU Construction

Families in San Jose, CA are discovering that adding an accessory dwelling unit is one of the most practical investments they can make. ADU construction provides 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 bring these projects to life with precision and integrity.

The demand for ADU construction has surged 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 supported 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 works.

At Brother & Brother Builders, we draw on extensive 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 functional. Should you want to learn about what ADU construction could look like on your property, this guide covers everything you need to know.

What Is ADU Construction?

ADU construction describes the process of engineering, filing for, and completing 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 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 basement or interior conversions.

Mechanically, the process begins with a thorough property evaluation, where our builders evaluate setbacks, zoning, utility access, and structural feasibility. From there, blueprints are prepared and submitted to the relevant municipal authority. Once more info approvals are in place, ADU construction enters the physical build phase — which includes foundation work, framing, roofing, plumbing, electrical, insulation. The result is a move-in-ready living unit attached to or separate 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 HVAC and drainage must be sized for independent daily use. Brother & Brother Builders approaches every build with the same professional rigor we bring to full custom home projects.

Key Advantages ADU Construction

• Higher Resale Potential — ADU construction adds measurable market value to your property, often returning more than the build cost when it's time to sell.
• Revenue Generation — A completed ADU can be rented as a long-term rental or short-term vacation unit, generating steady monthly revenue for the homeowner.
• Multi-Generational Living — ADU construction gives aging parents a comfortable home of their own without leaving the property.
• Design Flexibility — From open-plan one-bedrooms, ADU construction can be tailored to your household's priorities.
• Faster Permitting in California — Recent state legislation has minimized the red tape associated with ADU construction, creating a path that is faster and more cost-efficient than ever before.
• Responsible Property Development — Building an ADU maximizes the land you already own instead of requiring new development, which contributes to sustainability goals.
• Privacy for All Residents — Unlike a bedroom addition, ADU construction delivers a genuinely independent unit where tenants live autonomously.
• Long-Term Investment Security — A well-built ADU holds its value for decades, providing both functional space and financial upside.

The ADU Construction Process 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 can be built before any time is invested in drawings.
2. Blueprint Development and Layout Design — Experienced draftspeople create precise architectural drawings tailored to your needs. Layouts are carefully considered to optimize daily use.
3. Permitting and City Approval — ADU construction in San Jose requires submitting plans to the city's building department for review and approval. Our team handles all submissions on your behalf, addressing any city comments promptly.
4. Excavation and Foundation Installation — Once permits are issued, the build starts. This involves leveling and prepping the ground, laying the structural base, and running initial plumbing and electrical conduits.
5. Structural Framing and Weatherproofing — Walls and roof systems go up followed by weatherproofing and exterior finish materials. During this step, the ADU becomes recognizable as a structure.
6. Mechanical, Electrical, and Plumbing Installation — Licensed subcontractors install the plumbing lines, electrical wiring, and HVAC systems that make the ADU ready for occupancy. Every system is reviewed at required milestones throughout ADU construction.
7. Interior Completion and City Sign-Off — Flooring, cabinetry, fixtures, paint are fitted and completed to the agreed design. A last official inspection issues the certificate of occupancy and your new space is cleared for use.

Who Is a Good Candidate for ADU Construction?

Homeowners who benefit most from ADU construction often belong to a few common profiles. If you are a homeowner with enough lot space to meet setback requirements, you're already well-positioned. Homeowners looking to generate income through rental are among the most financially driven ADU construction clients, along with families navigating multigenerational living situations.

Another strong candidate is someone who runs a small business and wants a separate office or studio space that doesn't interfere with your family's daily life. Property investors and rental owners who are building a portfolio are also well suited for ADU construction, since the return on investment is well-documented.

Situations where ADU construction may not be the best first step include lots that are below minimum size thresholds. Parcels in historic districts or HOA-restricted communities may face additional constraints. Our experts will evaluate each property case by case to advise you on what's feasible.

ADU Construction FAQ

How long does ADU construction typically 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. City review on its own can take two to four months in San Jose, so planning ahead matters. Smaller detached units may complete more quickly, 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. Locally, ADU construction typically ranges from $150,000 to $400,000 or more for a detached new build. Garage conversions are generally priced lower, sometimes starting around $80,000 depending on scope. A detailed estimate can only be produced following a thorough property review.

Is ADU construction intrusive 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 usually easier to live alongside, since the crew operates at a distance from your living areas. Garage conversions or attached additions may create short-term inconveniences during specific stages like framing or MEP rough-in. Brother & Brother Builders keeps you informed about upcoming work and timelines.

Do I need to vacate the property during ADU construction?

For the majority of homeowners, you do not need to vacate your house during ADU construction. Most builds are designed so that you remain on the property throughout the build. Certain situations could require a brief departure if interior conversion work touches shared systems in ways that require short-term access disruption. Our construction supervisors will flag these situations during the planning phase.

How long will an ADU built through professional ADU construction hold up?

A well-built ADU can be expected to last as long as the main residence — often several decades with routine maintenance. How long it lasts comes down to the systems installed, how consistently minor repairs are addressed, and whether systems like roofing and plumbing are serviced regularly. We select high-quality components and follow all code requirements to protect your investment for the long haul.

ADU Construction for Local Homeowners

San Jose's neighborhoods offer a variety of property types that are perfectly suited for ADU construction. Property owners near the Almaden Valley area frequently see their parcels work well for both attached and detached projects. The Berryessa area have seen growing ADU activity as housing demand rises. If you're located closer to Evergreen, our team has likely worked nearby.

The City of San Jose's building department applies particular standards for ADU construction that require a builder familiar with local expectations. Access to infrastructure along thoroughfares like Monterey Road can impact the design approach for a given ADU project. Our team's knowledge of the San Jose permitting environment means smoother project delivery from the first meeting to the final inspection.

Book Your ADU Construction Planning Session Today

Should you be thinking about how to move forward with ADU construction, Brother & Brother Builders is the team to call. We bring licensed expertise in ADU construction including all types of project types — from small attached additions to fully independent secondary homes. Our approach opens with a comprehensive site assessment where we listen to your goals and share clear expectations of what's achievable.

Reach out to our team to begin the conversation. Even if you're just exploring the idea, we enjoy discuss timelines, costs, and design possibilities and give you the clarity you need to move forward. This type of project is a meaningful commitment — and we're committed to helping you get it right.

Brother & Brother Builders | 3109 Stevens Creek Boulevard | San Jose CA 95117 | (888) 412-2632