Expand Your Home with Professional ADU Construction
Property owners throughout San Jose, CA are finding that adding an accessory dwelling unit is one of the smartest investments they can make. ADU construction opens the door to a flexible new living space on your existing property — whether you want to generate rental income. Brother & Brother Builders has helped hundreds of local homeowners bring these projects to life with skill and transparency.
The popularity of ADU construction has surged in recent years, and it's easy to understand why. California state law has streamlined permitting for homeowners to construct these secondary units, and local municipalities like San Jose have encouraged the trend as a way to address housing needs. If you're planning a detached backyard cottage, a garage conversion, or an attached addition, ADU construction gives you more control over how your property serves your household.
At Brother & Brother Builders, we draw on extensive hands-on experience to every ADU construction project. Our team knows the San Jose building codes, the engineering considerations, and the design choices that make an ADU functional. When you're ready to explore 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 describes the process of designing, permitting, and building 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 entrance — 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 basement or interior conversions.
Mechanically, everything kicks off with a detailed site assessment, where our professionals evaluate lot dimensions, existing structures, soil conditions, and local code requirements. From there, blueprints are prepared and submitted to the relevant municipal authority. Once approvals are in place, ADU construction transitions to the physical build phase — which includes foundation work, framing, mechanical systems, weatherproofing, and interior finishing. The result is a completely finished living unit connected to or independent of your main home.
The difference between a good and a great ADU build is the attention to detail at every stage. Materials must be selected to complement the existing structure. Systems like wiring and water supply must be sized for independent daily use. Brother & Brother Builders treats each project with the same professional rigor we use on major 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.
- Revenue Generation — A completed ADU may be listed as a long-term rental or short-term vacation unit, providing a consistent income stream for the homeowner.
- Housing for Extended Family — ADU construction offers family members a self-contained residence without losing proximity to the family.
- Customization Options — From modern studio layouts, ADU construction can be tailored to your household's priorities.
- Streamlined Approval Process — Recent state legislation has reduced the barriers and delays associated with ADU construction, making the process that is faster and less expensive than ever before.
- Efficient Use of Your Lot — 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 delivers a genuinely independent unit where occupants have full privacy.
- Long-Term Investment Security — A well-built ADU remains an asset for many years and generates both livable square footage and monetary benefit.
The ADU Construction Procedure Step by Step
- Property Walkthrough and Feasibility Check — Our experts review your property to evaluate setbacks, lot coverage limits, and utility connections. This phase answers exactly what's possible before any money is spent on design.
- Custom Design and Architectural Planning — Experienced draftspeople create precise architectural drawings based on your goals. Layouts are carefully considered to optimize daily use.
- Filing for Building Permits — ADU construction in San Jose demands documentation to the city's building department for review and approval. We manage this entire process on your behalf, addressing any city comments promptly.
- Ground Prep and Structural Base — Once permits are issued, physical construction begins. This covers land preparation, laying the structural base, and running initial plumbing and electrical conduits.
- Structural Framing and Weatherproofing — The structural frame is erected followed by roofing, siding, windows, and exterior doors. This phase, the ADU transforms from a concept to a building.
- Mechanical, Electrical, and Plumbing Installation — Licensed subcontractors install the water supply, drain lines, and electrical panel that make the ADU ready for occupancy. All work is inspected at each code checkpoint throughout ADU construction.
- Interior Completion and City Sign-Off — Trim, appliances, tile, and lighting are fitted and completed to the agreed design. A closing municipal review issues the certificate of occupancy and the unit is officially approved for use.
Who Is a Right Fit for ADU Construction?
Homeowners who benefit most from ADU construction often belong to a few recognizable groups. If you are a homeowner with enough lot space to meet setback requirements, you're already in a good starting place. Homeowners wanting to add a revenue stream through rental are among the most financially driven 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 separate office or studio space that is distinct from your family's daily life. Property investors and rental owners who are building a portfolio are also a natural fit for ADU construction, since the return on investment is well-documented.
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. Our experts will evaluate 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 usually runs between six to fourteen months, depending on design complexity and city review schedules. City review on its own can take a significant portion of the overall timeline in San Jose, so starting early is important. Smaller detached click here units can move faster, while multi-room detached cottages fall toward the upper end of the timeline.
What does ADU construction typically cost?
Budget requirements differ based on whether it's a conversion or new construction. In the San Jose area, ADU construction typically ranges from $150,000 to $400,000 or more for a standalone backyard unit. Garage conversions tend to cost less, sometimes in the $80,000 to $150,000 range. A precise cost projection can only be produced following 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 create short-term inconveniences during certain phases of construction. Brother & Brother Builders keeps you informed about what to expect at each stage.
Do I need to leave my home during ADU construction?
For the majority of homeowners, you do not need 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 significant structural connections require temporary shutoffs in ways that require short-term access disruption. Our project managers will flag these situations during the pre-construction consultation.
How long will an ADU built through professional ADU construction hold up?
An ADU constructed with quality materials should last as long as the main residence — typically 50 years or more. Longevity is tied to the standard of construction, how consistently minor repairs are addressed, and if mechanical components are maintained on schedule. We select residential-grade products rated for longevity and build to current California residential standards to ensure lasting performance.
ADU Construction for San Jose Homeowners
The communities throughout San Jose provide a diverse mix of property types that are ideally positioned for ADU construction. Property owners near the Almaden Valley area often discover their properties work well for both attached and detached projects. The Berryessa area are seeing more homeowners add secondary units as families expand. If you're located closer to Evergreen, our team has likely worked nearby.
Local regulatory bodies in this area has developed specific protocols for ADU construction that require a builder familiar with local expectations. Proximity to transit corridors can impact the design approach for a given ADU project. Our familiarity with this region's building landscape means fewer surprises from kickoff through certificate of occupancy.
Schedule Your ADU Construction Consultation Today
Should you be thinking about how to explore what an ADU could look like on your lot, Brother & Brother Builders is here to help. We bring years of hands-on experience in ADU construction including all types of project types — from modest studio builds to fully independent secondary homes. The process begins with a detailed, no-pressure consultation where we listen to your goals and give you a realistic picture of what the project will involve.
Reach out to our team to schedule a site visit. Even if you're just exploring the idea, we enjoy answer questions, share examples of our work and make sure you feel confident before committing. This type of project is a meaningful commitment — and we're committed to helping you get it right.
Brother & Brother Builders | 3109 Stevens Creek Boulevard | San Jose CA 95117 | (888) 412-2632