Unlock New Space with Quality 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 creates 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 bring these projects to life with skill and care.

The popularity of ADU construction has grown rapidly in recent years, and it's not hard to see why. California state law has streamlined permitting for homeowners to build these secondary units, and local municipalities like San Jose have supported 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 offers greater control over how your property works.

At Brother & Brother Builders, we bring years of hands-on experience to every ADU construction project. Our team is familiar with city and county requirements, the engineering details, and the design choices that make an ADU truly livable. Should you want to learn about what ADU construction could look like on your property, this guide explains everything you need to know.

What Is the ADU Construction Process?

ADU construction involves the process of engineering, filing for, and completing 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 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 process begins with a detailed site assessment, where our builders 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 enters the physical build phase — which covers everything from foundational work, framing, HVAC, drywall, flooring, and exterior finishes. The result is a completely finished living unit adjacent to or detached from your main home.

What sets quality ADU construction apart is the level of craftsmanship at every stage. Components should be specified to align with the neighborhood's character. Systems like wiring and water supply must be sized for independent daily use. Brother & Brother Builders approaches every build with the same technical more info discipline we bring to full 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.
• Revenue Generation — A completed ADU may be listed as a long-term rental or short-term vacation unit, generating steady monthly revenue for the homeowner.
• Space for Loved Ones — 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 the intended occupant's lifestyle.
• Faster Permitting in California — Recent state legislation has reduced 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 works within your current footprint instead of consuming open land, which supports broader sustainability goals.
• Privacy for All Residents — Unlike a bedroom addition, ADU construction creates a truly separate unit where residents have their own space.
• Lasting Financial Benefit — A well-built ADU holds its value for many years and generates both functional space and financial upside.

The ADU Construction Procedure Step by Step

1. Property Walkthrough and Feasibility Check — Our builders assess your property to analyze zoning rules, slope conditions, and available square footage. This step tells you exactly what ADU types will work before any time is invested in drawings.
2. Custom Design and Architectural Planning — Our design team create comprehensive blueprints based on your goals. Every square foot is planned to create practical, comfortable living.
3. Permitting and City Approval — ADU construction in San Jose demands documentation to the city's building department for inspection and clearance. Brother & Brother Builders coordinates the permitting on your behalf, responding to review feedback promptly.
4. Ground Prep and Structural Base — Once permits are approved, on-site work kicks off. This involves leveling and prepping the ground, completing foundation work, and establishing utility connections.
5. Shell Construction and Exterior Finishing — Framing is completed followed by roofing, siding, windows, and exterior doors. During this step, the ADU becomes recognizable as a structure.
6. Mechanical, Electrical, and Plumbing Installation — Licensed subcontractors install the heating, cooling, drainage, and power infrastructure that make the ADU operationally complete. Inspections are completed at designated stages throughout ADU construction.
7. Interior Finishing and Final Inspections — Flooring, cabinetry, fixtures, paint are fitted and completed to the agreed design. A closing municipal review confirms the unit is code-compliant and the unit is officially approved for use.

Who Is a Strong Candidate for ADU Construction?

People who see the greatest return from ADU construction typically fall into a few recognizable groups. If you own a single-family home with available square footage under zoning rules, you're already well-positioned. Homeowners hoping to offset mortgage costs through rental are among the most common ADU construction clients, along with families navigating multigenerational living situations.

You may also be someone who works from home and wants a private work environment that is distinct from your family's daily life. Landlords and real estate investors who are building a portfolio are also well suited for ADU construction, since rental income frequently offsets build costs.

Situations where ADU construction may not be the best first step include properties with significant setback limitations. Very small lots or properties with easements may need a modified approach. Brother & Brother Builders reviews each property individually and honestly to recommend the right path forward.

ADU Construction Frequently Asked Questions

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

The total process for ADU construction commonly spans six to fourteen months, influenced by the type of unit being built and how quickly approvals come through. City review on its own can take several months in San Jose, so beginning the process sooner rather than later is wise. Straightforward interior conversions can move faster, while larger new construction ADUs require more time.

What does ADU construction usually run in terms of budget?

Costs vary widely based on project complexity and finishes selected. For most projects in this region, ADU construction commonly costs $150,000 to $400,000 or more for a detached new build. Garage conversions tend to cost less, sometimes starting around $80,000 depending on scope. A detailed estimate can only be developed after a full site assessment.

Is ADU construction disruptive while it's underway?

The level of disruption depends on whether you're converting existing space or building new. Standalone ADU projects are generally the least intrusive, since the construction zone is separate. Projects that connect to the main structure may require temporary access during specific stages like framing or MEP rough-in. Brother & Brother Builders keeps you informed about any phases that may affect your routine.

Do I need to vacate the property during ADU construction?

Generally speaking, you do not need to vacate your primary residence during ADU construction. Most job sites are structured to allow you continue living in the home throughout the construction timeline. Exceptions may arise if significant structural connections require temporary shutoffs in ways that briefly affect habitability. The team at Brother & Brother Builders will discuss these scenarios during the kickoff meeting.

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

A well-built ADU is designed to last as long as your primary home — typically 50 years or more. Longevity is tied to the systems installed, whether the unit is properly cared for, and whether systems like roofing and plumbing are serviced regularly. Brother & Brother Builders specifies high-quality components and comply with all local building codes to deliver a structure that stands the test of time.

ADU Construction for San Jose 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 often discover their properties work well for both attached and detached projects. Neighborhoods near Blossom Hill Road are seeing more homeowners add secondary units as housing demand rises. Whether your property is near downtown San Jose, our team knows the permitting landscape well.

Local regulatory bodies in this area applies particular standards for ADU construction that experienced builders know well. Proximity to transit corridors can impact the design approach for a given ADU project. Our familiarity with the San Jose permitting environment means smoother project delivery from design through the final walkthrough.

Book Your ADU Construction Assessment Today

Should you be thinking about how to add an ADU to your property, Brother & Brother Builders is here to help. We bring licensed expertise in ADU construction for many different project types — from modest studio builds to multi-room backyard residences. The process begins with a comprehensive site assessment 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, we enjoy walk through your options, review completed projects and make sure you feel confident before committing. Building an ADU is a major decision — and we're committed to helping you get it right.

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