Expert ADU Construction Services for Homeowners

Unlock New Space with Quality ADU Construction

Homeowners across San Jose, CA are finding that adding an accessory dwelling unit is one of the most rewarding investments they can make. ADU construction opens the door to a versatile new living space on your existing property — whether you want to create a private workspace. Brother & Brother Builders has helped hundreds of local homeowners turn these plans to life with craftsmanship and care.

The demand for ADU construction has increased significantly in recent years, and it's easy to understand why. 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 expand the housing supply. 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 project. Our team is familiar with city and county requirements, the engineering considerations, and the planning steps that make an ADU functional. If you've been thinking about what ADU construction could do for your property, this guide explains everything you need to know.

What Is ADU Construction?

ADU construction refers to 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 — including a kitchen, bathroom, sleeping area, and its own access point — that is located on the same parcel as a primary residence. ADU construction comes here in multiple configurations, including detached backyard units, attached additions, garage conversions, and even below-grade dwelling units.

Mechanically, the process begins with a comprehensive review of your lot, where our team evaluate property boundaries, available square footage, and infrastructure capacity. From there, design plans are prepared and submitted to the city for permit approval. Once approvals are in place, ADU construction transitions to the physical build phase — which encompasses site preparation, framing, mechanical systems, weatherproofing, and interior finishing. The result is a move-in-ready living unit adjacent to or detached from your main home.

What sets quality ADU construction apart is the attention to detail at every stage. Components should be specified to align with the neighborhood's character. Systems like plumbing and electrical must be sized for independent daily use. Brother & Brother Builders treats each project with the same technical discipline we use on major custom home projects.

Key Benefits ADU Construction

• Increased Property Value — 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 is leasable as a long-term rental or short-term vacation unit, creating ongoing passive income for the homeowner.
• Housing for Extended Family — ADU construction gives aging parents a private, independent living space without leaving the property.
• Design Flexibility — From open-plan one-bedrooms, ADU construction may be customized to your household's priorities.
• Simplified Regulatory Path — Recent state legislation has minimized the red tape associated with ADU construction, resulting in a timeline that is faster and less expensive than ever before.
• Sustainable Land Use — Building an ADU uses your existing lot instead of consuming open land, which supports broader sustainability goals.
• Independent Living Areas — 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 decades, providing 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's possible before any resources go toward planning.
2. Custom Design and Architectural Planning — Licensed architects and designers create detailed floor plans tailored to your needs. Space is thoughtfully allocated to maximize function and livability.
3. Permitting and City Approval — ADU construction in San Jose demands documentation to the city's building department for sign-off and verification. Brother & Brother Builders coordinates the permitting 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, laying the structural base, and setting up utilities.
5. Structural Framing and Weatherproofing — Walls and roof systems go up followed by insulation, sheathing, and exterior cladding. At this stage, the ADU becomes recognizable as a structure.
6. Mechanical, Electrical, and Plumbing Installation — Skilled tradespeople install the heating, cooling, drainage, and power infrastructure that make the ADU operationally complete. All work is inspected at each code checkpoint throughout ADU construction.
7. Interior Completion and City Sign-Off — Flooring, cabinetry, fixtures, paint are placed and inspected to your specifications. A last official inspection grants legal occupancy status and the ADU is ready for use.

Who Is a Strong Candidate for ADU Construction?

Homeowners who benefit most from ADU construction typically fall into a few clear categories. If you own a single-family home with available square footage under zoning rules, you're already in a good starting place. Homeowners wanting to add a revenue stream through rental are among the most common ADU construction clients, along with families navigating multigenerational living situations.

ADU construction also suits someone who runs a small business and wants a separate office or studio space that remains away from your family's daily life. Property investors and rental owners 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 lots that are below minimum size thresholds. Sites with underground infrastructure conflicts may require additional review. Brother & Brother Builders reviews each property on its own merits 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 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 custom detached builds fall toward the upper end of the timeline.

What does ADU construction usually run in terms of budget?

Costs vary widely based on the type and size of the ADU. In the San Jose area, ADU construction typically ranges from $150,000 to $400,000 or more for a standalone backyard unit. Garage conversions often come in under, sometimes between $75,000 and $140,000. A precise cost projection can only be developed after a full site assessment.

Is ADU construction disruptive while it's underway?

How much the build affects daily life depends on where the ADU is being built. New construction in the rear yard are typically less disruptive, since the construction zone is separate. Garage conversions or attached additions may require temporary access during key milestones. Our team communicates clearly about what to expect at each stage.

Do I need to vacate the property during ADU construction?

For the majority of homeowners, you are not required to vacate your main home during ADU construction. Most job sites are set up to let you stay in your primary unit throughout the build. Exceptions may arise if significant structural connections require temporary shutoffs in ways that temporarily impact livability. Our project managers will flag these situations during the pre-construction consultation.

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

Any ADU built to code with professional oversight should last as long as any standard residential structure — often several decades with routine maintenance. How long it lasts comes down to the standard of construction, how consistently minor repairs are addressed, and how proactively issues are resolved over time. Our builds use commercial-grade materials and build to current California residential standards to deliver a structure that stands the test of time.

ADU Construction for Local Homeowners

San Jose's neighborhoods offer a variety of property types that are well suited for ADU construction. Homeowners in the Willow Glen neighborhood often discover their properties accommodate detached backyard units nicely. The Berryessa area have seen growing ADU activity as housing demand rises. From neighborhoods near the Guadalupe River Park corridor to those near Branham Lane, our team has likely worked nearby.

Local regulatory bodies in this area has developed specific protocols for ADU construction that our team navigates routinely. Proximity to transit corridors can affect how quickly permits are approved for a given ADU project. Brother & Brother Builders' experience across these local conditions means smoother project delivery from kickoff through certificate of occupancy.

Start Your ADU Construction Planning Session Today

When you want to move forward with ADU construction, Brother & Brother Builders is the team to call. Our builders provide years of hands-on experience in ADU construction for many different project types — from simple garage conversions to fully independent secondary homes. Every project starts with a comprehensive site assessment where we listen to your goals and give you a realistic picture of what's achievable.

Reach out to our team to schedule a site visit. Even if you're just exploring the idea, our team is happy to walk through your options, review completed projects and give you the clarity you need to move forward. ADU construction is a significant investment — and our goal is to ensure it delivers real value.

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