Everything You Need to Know About ADU Construction

Transform Your Property with Quality ADU Construction

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

The interest in ADU construction has surged in recent years, and it's easy to understand why. California state law has streamlined permitting for homeowners to build these secondary units, and local municipalities like San Jose have embraced the trend as a way to expand the housing supply. Whether you want to build 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 apply deep hands-on experience to every ADU construction project. Our team is familiar with city and county requirements, the engineering details, and the planning steps that make an ADU functional. Should you want to learn about what ADU construction could look like on your property, this guide will walk you through everything you need to know.

What Is ADU Construction?

ADU construction involves 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 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 interior space reconfigurations.

Mechanically, the process begins with a comprehensive review of your lot, where our professionals evaluate setbacks, zoning, utility access, and structural feasibility. From there, design plans are prepared and submitted to the local building department. Once approvals are in place, ADU construction moves into the physical build phase — which encompasses site preparation, framing, mechanical systems, weatherproofing, and interior finishing. The result is a completely finished living unit attached to or separate from your main home.

What sets quality ADU construction apart is the depth of planning at every stage. Products need to be chosen to complement the existing structure. Systems like HVAC and drainage must be sized for independent daily use. Brother & Brother Builders handles every ADU construction job with the same professional rigor we apply to large-scale custom home projects.

Key Reasons to Choose ADU Construction

• Boosted Home Equity — ADU construction adds measurable market value to your property, often generating strong equity gains when it's time to sell.
• Monthly Cash Flow — A completed ADU is leasable as a long-term rental or short-term vacation unit, creating ongoing passive income for the homeowner.
• Space for Loved Ones — ADU construction offers family members a private, independent living space without leaving the property.
• Personalized Layouts — From modern studio layouts, ADU construction is adaptable to your specific needs.
• Faster Permitting in California — Recent state legislation has minimized the barriers and delays associated with ADU construction, making the process that is faster and more cost-efficient than ever before.
• Responsible Property Development — Building an ADU works within your current footprint instead of consuming open land, which aligns with sustainability goals.
• Separate Entrances and Spaces — Unlike a bedroom addition, ADU construction produces a fully self-contained unit where residents have their own space.
• Lasting Financial Benefit — A well-built ADU continues to produce returns for the long haul by offering both livable square footage and monetary benefit.

The ADU Construction Procedure Step by Step

1. Initial Property Assessment and Feasibility Review — Our team visits your property to analyze zoning rules, slope conditions, and available square footage. This stage clarifies exactly what can be built before any resources go toward planning.
2. Custom Design and Architectural Planning — Licensed architects and designers create comprehensive blueprints reflecting your priorities. Layouts are carefully considered to create practical, comfortable living.
3. Permitting and City Approval — 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, resolving any revision requests promptly.
4. Site Preparation and Foundation Work — Once permits are granted, physical construction begins. This involves leveling and prepping the ground, pouring the concrete foundation, and setting up utilities.
5. Framing, Roofing, and Exterior Work — Walls and roof systems go up followed by insulation, sheathing, and exterior cladding. During this step, the ADU becomes recognizable as a structure.
6. MEP Systems Rough-In — Skilled tradespeople install the plumbing lines, electrical wiring, and HVAC systems that make the ADU fully functional. Every system is reviewed at each code checkpoint throughout ADU construction.
7. Finishes, Fixtures, and Final Walkthrough — Trim, appliances, tile, and lighting are placed and inspected 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 recognizable groups. If you own a single-family home with enough lot space to meet setback requirements, you're already a strong candidate. 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 needs a dedicated professional workspace and wants a private work environment that remains away from your family's daily life. Real estate-minded homeowners who are building a portfolio are also well suited for ADU construction, since the return on investment is well-documented.

Those who should discuss alternatives first include properties with significant setback limitations. Very small lots or properties with easements may face additional constraints. Our experts will evaluate each property individually and honestly to recommend the right path forward.

ADU Construction FAQ

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

The total process for ADU construction typically ranges from six to fourteen months, based on the project scope and how quickly approvals come through. City review on its own can take a significant portion of the overall timeline in San Jose, so starting early is important. Straightforward interior conversions can move faster, while custom detached builds take longer to complete.

What does ADU construction cost in San Jose?

Costs vary widely based on whether it's a conversion or new construction. For most projects in this region, ADU construction commonly costs $150,000 to $400,000 or more for a fully custom construction. Garage conversions often come in under, sometimes between $75,000 and $140,000. A detailed estimate can only be given after completing a thorough property website review.

Is ADU construction intrusive while it's underway?

The day-to-day impact depends on where the ADU is being built. Detached backyard builds are typically less disruptive, since work happens away from the main house. 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 what to expect at each stage.

Do I need to vacate the property during ADU construction?

In most cases, you do not need to vacate your house during ADU construction. Most builds are set up to let you remain on the property throughout the construction timeline. There are edge cases if interior conversion work touches shared systems in ways that temporarily impact livability. Our construction supervisors will flag these situations during the kickoff meeting.

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

An ADU constructed with quality materials is designed to last as long as your primary home — typically 50 years or more. Durability depends to the standard of construction, whether the unit is properly cared for, and how proactively issues are resolved over time. Brother & Brother Builders specifies commercial-grade materials and follow all code requirements to protect your investment for the long haul.

ADU Construction for San Jose Homeowners

Residential areas across San Jose present a variety of property types that are perfectly suited for ADU construction. Homeowners in the Willow Glen neighborhood frequently see their parcels accommodate detached backyard units nicely. Neighborhoods near Blossom Hill Road are seeing more homeowners add secondary units as housing demand rises. From neighborhoods near the Guadalupe River Park corridor to those near Branham Lane, our team has likely worked nearby.

The City of San Jose's building department applies particular standards for ADU construction that our team navigates routinely. Location near major arterials like Story Road or Tully Road can impact the design approach for a given ADU project. Our team's knowledge of these local conditions means fewer surprises from design through the final walkthrough.

Schedule Your ADU Construction Planning Session Today

Should you be thinking about how to add an ADU to your property, Brother & Brother Builders is ready to guide you. Our builders provide years of hands-on experience in ADU construction across a wide range of project types — from modest studio builds to fully independent secondary homes. The process begins with a thorough and honest property review where we learn what you're trying to accomplish and provide an honest assessment of what's achievable.

Get in touch with our office to set up your consultation. No matter where you are in the decision-making process, our team is happy to 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 our goal is to ensure it delivers real value.

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