Unlock New Space with Expert ADU Construction
Families in San Jose, CA are realizing 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 guided hundreds of local homeowners bring these projects 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 encouraged the trend as a way to expand the housing supply. Whether you're building a detached backyard cottage, a garage conversion, or an attached addition, ADU construction offers greater control over how your property serves your household.
At Brother & Brother Builders, we bring years of hands-on experience to every ADU construction project. Our team understands the local permitting process, the engineering details, and the aesthetic decisions that make an ADU functional. Should you want to learn about what ADU construction could mean for your property, this guide covers everything you need to know.
What Is the ADU Construction Process?
ADU construction describes 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 entryway — that exists on the same lot 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, the work starts with a thorough property evaluation, where our builders evaluate setbacks, zoning, utility access, and structural feasibility. From there, design plans are prepared and submitted to the city for permit approval. Once permits are secured, ADU construction moves into the physical build phase — which covers everything from foundational work, framing, HVAC, drywall, flooring, and exterior finishes. The result is a move-in-ready living unit connected to or independent of your main home.
What sets quality ADU construction apart is the level of craftsmanship at every stage. Products need to be chosen to match the primary home's aesthetic. Systems like HVAC and drainage must be sized for independent daily use. Brother & Brother Builders approaches every build with the same high standards 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 may be listed as a long-term rental or short-term vacation unit, creating ongoing passive income for the homeowner.
- Multi-Generational Living — ADU construction gives aging parents a private, independent living space without moving to another neighborhood.
- Personalized Layouts — From open-plan one-bedrooms, ADU construction is adaptable to the intended occupant's lifestyle.
- Streamlined Approval Process — Recent state legislation has reduced the barriers and delays associated with ADU construction, creating a path that is faster and more affordable than ever before.
- Efficient Use of Your Lot — Building an ADU uses your existing lot instead of expanding urban sprawl, which aligns with sustainability goals.
- Privacy for All Residents — Unlike a bedroom addition, ADU construction produces a fully self-contained unit where residents have their own space.
- Long-Term Investment Security — A well-built ADU continues to produce returns for decades, providing both usable housing and equity growth.
The ADU Construction Procedure Step by Step
- Initial Property Assessment and Feasibility Review — Our team visits your property to evaluate setbacks, lot coverage limits, and utility connections. This step tells you exactly what ADU types will work before any money is spent on design.
- Custom Design and Architectural Planning — Our design team create precise architectural drawings reflecting your priorities. Space is thoughtfully allocated to maximize function and livability.
- Filing for Building Permits — ADU construction in San Jose requires submitting plans to the city's building department for review and approval. We manage this entire process on your behalf, responding to review feedback promptly.
- Site Preparation and Foundation Work — Once permits are granted, physical construction begins. This includes grading the site, laying the structural base, and running initial plumbing and electrical conduits.
- Framing, Roofing, and Exterior Work — Walls and roof systems go up followed by roofing, siding, windows, and exterior doors. During this step, the ADU transforms from a concept to a building.
- 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.
- Interior Finishing and Final Inspections — Flooring, cabinetry, fixtures, paint are installed and finished to the agreed design. A final city inspection issues the certificate of occupancy and your new space is cleared for use.
Who Is a Good Candidate for ADU Construction?
Property owners who are best suited from ADU construction generally fit within a few recognizable groups. If you have a residential property with enough lot space to meet setback requirements, you're already well-positioned. Homeowners wanting to add a revenue stream through rental are among the most common ADU construction clients, along with families accommodating adult children who need housing.
You may also be someone who works from home and wants a separate office or studio space that is distinct from your family's daily life. Property investors and rental owners who already own residential properties 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 properties with significant setback limitations. Very small lots or properties with easements may need a modified approach. Our experts will evaluate each property individually and honestly to advise you on what's feasible.
ADU Construction Frequently Asked Questions
How long does ADU construction generally take from start to finish?
The complete duration for ADU construction usually runs between six to fourteen months, depending on design complexity and city review schedules. The approval phase alone can take a significant portion of the overall timeline in San Jose, so planning ahead matters. Simpler garage conversions can move faster, while custom detached builds 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 typically ranges from $150,000 to $400,000 or more for a fully custom construction. Interior conversion projects often come in under, sometimes starting around $80,000 depending on scope. An accurate budget can only be produced following a thorough property review.
Is ADU construction intrusive while it's underway?
The day-to-day impact depends on the project's location on your property. New construction in the rear yard are typically less disruptive, since work happens away from the main house. Projects that connect to the main structure may involve some shared wall work during certain phases of construction. We provide advance notice about any phases that may affect your routine.
Do I need to vacate the property during ADU construction?
Generally speaking, you won't have to vacate your house during ADU construction. Most builds are structured to allow you remain on the property throughout the build. Certain situations could require a brief departure if interior conversion work touches shared systems in ways that require short-term access disruption. Our construction supervisors will flag these situations during the pre-construction consultation.
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. How long it lasts comes down to the quality of materials used, how consistently minor repairs are addressed, and if mechanical components are maintained on schedule. We select high-quality components and comply with all local building codes to ensure lasting performance.
ADU Construction for San Jose Homeowners
Residential areas across San Jose present a wide range of property types that are well suited for ADU construction. Property owners near the Almaden Valley area have found their lots work well for both attached and detached projects. Neighborhoods near Blossom Hill Road are increasingly popular for ADU construction as families expand. From neighborhoods near the Guadalupe River Park corridor to those near Branham Lane, our team knows the permitting landscape well.
The City of San Jose's building department has developed specific protocols for ADU construction that our team navigates routinely. Location near major arterials like Story Road or Tully Road can influence utility connection requirements for a given ADU project. Our familiarity with these local conditions means more accurate timelines and budgets from kickoff through certificate of occupancy.
Book Your ADU Construction Assessment Today
Should you be thinking about how to move forward with ADU construction, Brother & Brother Builders is the team to call. Our experts offer proven skills in ADU construction including all types of project types — from small attached get more info additions to fully independent secondary homes. The process begins with a detailed, no-pressure consultation where we learn what you're trying to accomplish and share clear expectations of what's achievable.
Get in touch with our office to schedule a site visit. No matter where you are in the decision-making process, we enjoy discuss timelines, costs, and design possibilities and give you the clarity you need to move forward. Building an ADU is a major decision — 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