Brother & Brother Builders

Transform Your Property with Professional ADU Construction

Families in San Jose, CA are realizing that adding an accessory dwelling unit is one of the most rewarding investments they can make. ADU construction opens the door to a flexible new living space on your existing property — whether you want to create a private workspace. Brother & Brother Builders has supported hundreds of local homeowners see these visions to life with skill and care.

The popularity of ADU construction has surged in recent years, and it's no mystery. California state law has streamlined permitting for homeowners to construct these secondary units, and local municipalities like San Jose have supported 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 offers greater control over how your property functions.

At Brother & Brother Builders, we apply deep hands-on experience to every website ADU construction project. Our team knows the San Jose building codes, the engineering requirements, and the planning steps that make an ADU beautiful. Should you want to learn 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 involves the process of planning, approving, and constructing an accessory dwelling unit on a residential property. An accessory dwelling unit is a self-contained living space — featuring a kitchen, bathroom, sleeping area, and its own entrance — that is located on the same parcel 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, the work starts with a thorough property evaluation, where our builders evaluate property boundaries, available square footage, and infrastructure capacity. From there, design plans are prepared and submitted to the relevant municipal authority. Once approvals are in place, ADU construction enters the physical build phase — which covers everything from foundational work, framing, HVAC, drywall, flooring, and exterior finishes. The result is a fully functional 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 complement the existing structure. Systems like plumbing and electrical must be designed to handle full-time occupancy. Brother & Brother Builders approaches every build with the same high standards we bring to full custom home projects.

Key Reasons to Choose ADU Construction

• Higher Resale Potential — 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, generating steady monthly revenue for the homeowner.
• Housing for Extended Family — ADU construction gives aging parents a self-contained residence without losing proximity to the family.
• Design Flexibility — From open-plan one-bedrooms, ADU construction is adaptable to your household's priorities.
• Simplified Regulatory Path — Recent state legislation has cut down the barriers and delays associated with ADU construction, creating a path that is faster and less expensive than ever before.
• Sustainable Land Use — Building an ADU maximizes the land you already own instead of expanding urban sprawl, which aligns with sustainability goals.
• Independent Living Areas — Unlike a bedroom addition, ADU construction delivers a genuinely independent unit where occupants have full privacy.
• Lasting Financial Benefit — A well-built ADU continues to produce returns for decades, providing both functional space and financial upside.

The ADU Construction Process Step by Step

1. Site Evaluation and Zoning Analysis — Our builders assess your property to determine what type of ADU is allowed and where it can be placed. This phase answers exactly what can be built before any money is spent on design.
2. Blueprint Development and Layout Design — Experienced draftspeople create precise architectural drawings based on your goals. Every square foot is planned to optimize daily use.
3. Filing for Building Permits — ADU construction in San Jose involves filing drawings to the city's building department for review and approval. Our team handles all submissions on your behalf, resolving any revision requests promptly.
4. Excavation and Foundation Installation — Once permits are granted, the build starts. This involves leveling and prepping the ground, pouring the concrete foundation, and establishing utility connections.
5. Framing, Roofing, and Exterior Work — Framing is completed followed by insulation, sheathing, and exterior cladding. During this step, the ADU becomes recognizable as a structure.
6. MEP Systems Rough-In — Certified technicians install the water supply, drain lines, and electrical panel that make the ADU fully functional. Inspections are completed at designated stages throughout ADU construction.
7. Interior Finishing and Final Inspections — Countertops, hardware, finishes, and fixtures are fitted and completed to the agreed design. A last official inspection confirms the unit is code-compliant and the unit is officially approved for use.

Who Is a Good Candidate for ADU Construction?

People who see the greatest return from ADU construction generally fit within a few common profiles. 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 financially driven ADU construction clients, along with families supporting elderly parents.

ADU construction also suits someone who works from home and wants a detached creative or business space that remains away from your family's daily life. Real estate-minded homeowners who already own residential properties are also prime candidates for ADU construction, since the return on investment is well-documented.

Those who should discuss alternatives first include sites with unusual utility access challenges. Sites with underground infrastructure conflicts may face additional constraints. Brother & Brother Builders reviews each property case by case to recommend the right path forward.

ADU Construction FAQ

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

The complete duration for ADU construction usually runs between six to fourteen months, based on the project scope and local permitting timelines. Permitting alone can take two to four months in San Jose, so starting early is important. Straightforward interior conversions can move faster, while multi-room detached cottages 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. Locally, ADU construction generally falls between $150,000 to $400,000 or more for a detached new build. Attached ADU additions often come in under, sometimes between $75,000 and $140,000. An accurate budget can only be produced following a thorough property review.

Is ADU construction intrusive while it's underway?

How much the build affects daily life depends on the project's location on your property. Standalone ADU projects are typically less disruptive, since work happens away from the main house. Projects that connect to the main structure may involve some shared wall work during key milestones. We provide advance notice about any phases that may affect your routine.

Do I need to leave my home during ADU construction?

Generally speaking, you do not need to vacate your house during ADU construction. Most job sites are designed so that you continue living in the home throughout the construction timeline. There are edge cases if interior conversion work touches shared systems in ways that briefly affect habitability. The team at Brother & Brother Builders will walk you through any potential disruptions during the planning phase.

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

A well-built ADU can be expected to last as long as your primary home — indefinitely with proper upkeep. Longevity is tied to the quality of materials used, how well routine maintenance is performed, and whether systems like roofing and plumbing are serviced regularly. Brother & Brother Builders specifies commercial-grade materials and follow all code requirements to ensure lasting performance.

ADU Construction for Local Homeowners

San Jose's neighborhoods offer a wide range of property types that are ideally positioned 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 housing demand rises. If you're located closer to Evergreen, our team has project experience in the area.

San Jose's permitting office has developed specific protocols for ADU construction that experienced builders know well. Access to infrastructure along thoroughfares like Monterey Road can influence utility connection requirements for a given ADU project. Brother & Brother Builders' experience across these local conditions means more accurate timelines and budgets from the first meeting to the final inspection.

Start Your ADU Construction Assessment Today

If you're ready to add an ADU to your property, Brother & Brother Builders is ready to guide you. We bring years of hands-on experience in ADU construction across a wide range of project types — from small attached additions to fully independent secondary homes. Our approach opens with a thorough and honest property review where we listen to your goals and share clear expectations of what ADU construction on your property will look like.

Reach out to our team 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 make sure you feel confident before committing. 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