Expand Your Home with Expert ADU Construction
Families in San Jose, CA are finding that adding an accessory dwelling unit is one of the most practical investments they can make. ADU construction provides a powerful new living space on your existing property — whether you want to house a family member. Brother & Brother Builders has helped hundreds of local homeowners see these visions to life with craftsmanship and transparency.
The popularity of ADU construction has increased significantly 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. 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 functions.
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 details, and the design choices that make an ADU functional. When you're ready to explore what ADU construction could mean for your property, this guide will walk you through 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 fully independent living space — featuring 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, the work starts with a thorough property evaluation, where our team evaluate setbacks, zoning, utility access, and structural feasibility. From there, design plans are prepared and submitted to the local building department. Once permits are secured, ADU construction moves into the physical build phase — which encompasses site preparation, framing, roofing, plumbing, electrical, insulation. The result is a move-in-ready living unit connected to or independent of your main home.
The difference between a good and a great ADU build is the depth of planning at every stage. Components should be specified to align with the neighborhood's character. Systems like HVAC and drainage 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 Reasons to Choose ADU Construction
- Increased Property Value — ADU construction contributes significant 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 offers family members a comfortable home of their own without losing proximity to the family.
- Customization Options — From open-plan one-bedrooms, ADU construction can be tailored to the intended occupant's lifestyle.
- Simplified Regulatory Path — Recent state legislation has minimized the permitting obstacles associated with ADU construction, creating a path that is faster and less expensive than ever before.
- Sustainable Land Use — Building an ADU maximizes the land you already own instead of consuming open land, which contributes to sustainability goals.
- Independent Living Areas — Unlike a bedroom addition, ADU construction produces a fully self-contained unit where occupants have full privacy.
- Lasting Financial Benefit — A well-built ADU holds its value for many years and generates both livable square footage and monetary benefit.
The ADU Construction Procedure Step by Step
- Initial Property Assessment and Feasibility Review — Our builders assess your property to analyze zoning rules, slope conditions, and available square footage. This step tells you exactly what's possible before any money is spent on design.
- Custom Design and Architectural Planning — Experienced draftspeople create precise architectural drawings tailored to your needs. Every square foot is planned to create practical, comfortable living.
- Permit Submission and Municipal Review — ADU construction in San Jose involves filing drawings to the city's building department for review and approval. Our team handles all submissions on your behalf, responding to review feedback promptly.
- Ground Prep and Structural Base — Once permits are issued, on-site work kicks off. This covers land preparation, completing foundation work, and setting up utilities.
- 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.
- 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.
- Finishes, Fixtures, and Final Walkthrough — 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 Right Fit for ADU Construction?
Property owners who are best suited from ADU construction generally fit within a few recognizable groups. If you are a homeowner 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 navigating multigenerational living situations.
ADU construction also suits someone who works from home and wants a detached creative or business space that remains away from your family's daily life. Landlords and real estate investors who are building a portfolio are also prime candidates for ADU construction, since rental income frequently offsets build costs.
Homeowners who may want to pause and evaluate include lots that are below minimum size thresholds. Very small lots or properties with easements may face additional constraints. Our team can assess each property case by case to advise you on what's feasible.
ADU Construction Common Questions Answered
How long does ADU construction usually take from start to finish?
The full timeline 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 a significant portion of the overall timeline in San Jose, so starting early is important. Simpler garage conversions often finish in the lower end of the range, while multi-room detached cottages fall toward the upper end of the timeline.
What does ADU construction typically cost?
Costs vary widely based on whether it's a conversion or new construction. Locally, ADU construction commonly costs $150,000 to $400,000 or more for a standalone backyard unit. Garage conversions tend to cost less, sometimes starting around $80,000 depending on scope. A detailed estimate can only be produced following a thorough property review.
Is ADU construction disruptive while it's underway?
How much the build affects daily life depends on whether you're converting existing space or building new. Standalone ADU projects are generally the least intrusive, since work happens away from the main house. Projects that connect to the main structure may involve some shared wall work during key milestones. We provide advance notice 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 builds are set up to let you continue living in the home throughout the build. Certain situations could require a brief departure if interior conversion work touches shared systems in ways that temporarily impact livability. Our construction supervisors will walk you through any potential disruptions during the pre-construction consultation.
How long will an ADU built through professional ADU construction remain in good condition?
A well-built ADU should last as long as the main residence — indefinitely with proper upkeep. How long it lasts comes down to the standard of construction, whether the unit is properly cared for, and whether systems like roofing and plumbing are serviced regularly. We select high-quality components and follow all check here code requirements to deliver a structure that stands the test of time.
ADU Construction for Local Homeowners
The communities throughout San Jose provide a wide range of property types that are ideally positioned for ADU construction. Homeowners in the Willow Glen neighborhood frequently see their parcels accommodate detached backyard units nicely. Neighborhoods near Blossom Hill Road are increasingly popular for ADU construction as multigenerational living becomes more common. 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 follows defined procedures for ADU construction that require a builder familiar with local expectations. Proximity to transit corridors can influence utility connection requirements for a given ADU project. Our familiarity with the San Jose permitting environment means fewer surprises from kickoff through certificate of occupancy.
Start Your ADU Construction Planning Session Today
Should you be thinking about how to add an ADU to your property, Brother & Brother Builders is the team to call. Our builders provide proven skills in ADU construction across a wide range of project types — from small attached additions to multi-room backyard residences. The process begins with a thorough and honest property review where we listen to your goals and share clear expectations of what ADU construction on your property will look like.
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. This type of project is a meaningful commitment — 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