Transform Your Property with Expert 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 see these visions to life with craftsmanship and care.
The demand for ADU construction has increased significantly 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 embraced the trend as a way to increase density responsibly. Whether you're building 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 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 aesthetic decisions that make an ADU truly livable. If you've been thinking about what ADU construction could mean for your property, this guide will walk you through everything you need to know.
What Is an ADU Build?
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 complete living space — including a kitchen, bathroom, sleeping area, and its own entryway — that sits on the same property as a primary residence. ADU construction comes in multiple configurations, including detached backyard units, attached additions, garage conversions, and even interior space reconfigurations.
Mechanically, the work starts with a thorough property evaluation, where our builders evaluate lot dimensions, existing structures, soil conditions, and local code requirements. From there, more info blueprints are prepared and submitted to the local building department. Once permits are secured, ADU construction transitions to the physical build phase — which encompasses site preparation, framing, mechanical systems, weatherproofing, and interior finishing. The result is a fully functional living unit adjacent to or detached from your main home.
What separates excellent ADU construction from an average project is the depth of planning at every stage. Materials must be selected to complement the existing structure. Systems like HVAC and drainage must be built for long-term residential demand. Brother & Brother Builders handles every ADU construction job with the same technical discipline we bring to full custom home projects.
Key Benefits ADU Construction
- Increased Property Value — ADU construction delivers real market value to your property, often returning more than the build cost when it's time to sell.
- Monthly Cash Flow — A completed ADU can be rented as a long-term rental or short-term vacation unit, providing a consistent income stream for the homeowner.
- Housing for Extended Family — ADU construction provides adult children a self-contained residence without losing proximity to the family.
- Personalized Layouts — From modern studio layouts, ADU construction may be customized to the intended occupant's lifestyle.
- Streamlined Approval Process — Recent state legislation has minimized the red tape 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 requiring new development, which contributes to sustainability goals.
- Independent Living Areas — 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 decades, providing both usable housing and equity growth.
The ADU Construction Process Step by Step
- Property Walkthrough and Feasibility Check — Our experts review your property to determine what type of ADU is allowed and where it can be placed. This phase answers exactly what's possible before any time is invested in drawings.
- Architectural Drafting and Space Planning — Experienced draftspeople create comprehensive blueprints based on your goals. Layouts are carefully considered to create practical, comfortable living.
- Filing for Building Permits — 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, responding to review feedback promptly.
- Site Preparation and Foundation Work — Once permits are approved, on-site work kicks off. This includes grading the site, laying the structural base, and setting up utilities.
- Structural Framing and Weatherproofing — Framing is completed followed by weatherproofing and exterior finish materials. During this step, the ADU takes its visible shape.
- Mechanical, Electrical, and Plumbing Installation — Skilled tradespeople install the plumbing lines, electrical wiring, and HVAC systems that make the ADU ready for occupancy. Inspections are completed at required milestones throughout ADU construction.
- Interior Finishing and Final Inspections — Countertops, hardware, finishes, and fixtures are fitted and completed to the approved plan. A last official inspection confirms the unit is code-compliant and the ADU is ready for use.
Who Is a Strong Candidate for ADU Construction?
Property owners who are best suited from ADU construction often belong to a few recognizable groups. If you have a residential property with available square footage under zoning rules, you're already in a good starting place. Homeowners hoping to offset mortgage costs through rental are among the most motivated ADU construction clients, along with families accommodating adult children who need housing.
Another strong candidate is someone who needs a dedicated professional workspace and wants a detached creative or business space that is distinct from your family's daily life. Real estate-minded homeowners who want to maximize their land are also prime candidates for ADU construction, since the return on investment is well-documented.
Situations where ADU construction may not be the best first step include sites with unusual utility access challenges. Very small lots or properties with easements may need a modified approach. Our experts will evaluate each property on its own merits to recommend the right path forward.
ADU Construction Frequently Asked Questions
How long does ADU construction typically take from start to finish?
The full timeline for ADU construction usually runs between six to fourteen months, based on the project scope and local permitting timelines. City review on its own can take several months in San Jose, so beginning the process sooner rather than later is wise. Smaller detached units may complete more quickly, while larger new construction ADUs fall toward the upper end of the timeline.
What does ADU construction typically cost?
Costs vary widely based on project complexity and finishes selected. Locally, ADU construction generally falls between $150,000 to $400,000 or more for a fully custom construction. Interior conversion projects 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 difficult to live through while it's underway?
The level of disruption depends on where the ADU is being built. Standalone ADU projects are usually easier to live alongside, since work happens away from the main house. Interior conversions may require temporary access during specific stages like framing or MEP rough-in. Brother & Brother Builders keeps you informed about what to expect at each stage.
Do I need to vacate the property during ADU construction?
In most cases, you are not required to vacate your main home during ADU construction. Most job sites are designed so that you stay in your primary unit throughout the build. There are edge cases if interior conversion work touches shared systems in ways that temporarily impact livability. The team at Brother & Brother Builders will discuss these scenarios during the pre-construction consultation.
How long will an ADU built through professional ADU construction last?
An ADU constructed with quality materials should last as long as your primary home — typically 50 years or more. Longevity is tied to the systems installed, how well routine maintenance is performed, and whether systems like roofing and plumbing are serviced regularly. Brother & Brother Builders specifies residential-grade products rated for longevity and build to current California residential standards to deliver a structure that stands the test of time.
ADU Construction for Local Homeowners
The communities throughout San Jose provide a diverse mix of property types that are perfectly suited for ADU construction. Residents in the Rose Garden district 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. Whether your property is near downtown San Jose, our team knows the permitting landscape well.
Local regulatory bodies in this area has developed specific protocols for ADU construction that our team navigates routinely. Access to infrastructure along thoroughfares like Monterey Road can affect how quickly permits are approved for a given ADU project. Our team's knowledge of the San Jose permitting environment means fewer surprises from design through the final walkthrough.
Book Your ADU Construction Planning Session Today
If you're ready to explore what an ADU could look like on your lot, Brother & Brother Builders is ready to guide you. Our builders provide licensed expertise in ADU construction for many different project types — from small attached additions to large custom detached cottages. Every project starts with a thorough and honest property review where we learn what you're trying to accomplish and provide an honest assessment of what ADU construction on your property will look like.
Contact Brother & Brother Builders to begin the conversation. Even if you're just exploring the idea, our team is happy to discuss timelines, costs, and design possibilities 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