Expert ADU Construction Services for Homeowners

Transform Your Property with Quality ADU Construction

Property owners throughout San Jose, CA are realizing that adding an accessory dwelling unit is one of the smartest investments they can make. ADU construction creates a versatile new living space on your existing property — whether you want to generate rental income. Brother & Brother Builders has guided hundreds of local homeowners see these visions to life with craftsmanship and integrity.

The interest in ADU construction has increased significantly in recent years, and it's not hard to see why. California state law has simplified the process for homeowners to add these secondary units, and local municipalities like San Jose have supported the trend as a way to increase density responsibly. If you're planning a detached backyard cottage, a garage conversion, or an attached addition, ADU construction provides increased control over how your property functions.

At Brother & Brother Builders, we apply deep hands-on experience to every ADU construction build. Our team is familiar with city and county requirements, the engineering requirements, and the planning steps that make an ADU truly livable. Should you want to learn about what ADU construction could mean for your property, this guide covers everything you need to know.

What Is ADU Construction?

ADU construction involves the process of planning, approving, and constructing an accessory dwelling unit on a residential property. An accessory dwelling unit is a fully independent living space — including a kitchen, bathroom, sleeping area, and its own access point — 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 below-grade dwelling units.

Mechanically, the process begins with a detailed site assessment, where our team evaluate lot dimensions, existing structures, soil conditions, and local code requirements. From there, blueprints are prepared and submitted to the local building department. Once approvals are in place, ADU construction transitions to the physical build phase — which includes foundation work, framing, roofing, plumbing, electrical, insulation. 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 depth of planning at every stage. Components should be specified to match the primary home's aesthetic. Systems like HVAC and drainage must be designed to handle full-time occupancy. Brother & Brother Builders handles every ADU construction job with the same professional rigor 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.
• Monthly Cash Flow — A completed ADU is leasable as a long-term rental or short-term vacation unit, creating ongoing passive income for the homeowner.
• Space for Loved Ones — ADU construction gives aging parents a private, independent living space without losing proximity to the family.
• Personalized Layouts — From two-bedroom configurations, ADU construction can be tailored to your specific needs.
• Streamlined Approval Process — Recent state legislation has cut down the red tape associated with ADU construction, resulting in a timeline that is faster and more cost-efficient than ever before.
• Responsible Property Development — Building an ADU uses your existing lot instead of requiring new development, which aligns with sustainability goals.
• Separate Entrances and Spaces — Unlike a bedroom addition, ADU construction delivers a genuinely independent unit where residents have their own space.
• Durable Return on Investment — A well-built ADU remains an asset for decades, providing both usable housing and equity growth.

The ADU Construction Journey Step by Step

1. Site Evaluation and Zoning Analysis — Our experts review your property to determine what type of ADU is allowed and where it can be placed. This phase answers exactly what ADU types will work before any money is spent on design.
2. Custom Design and Architectural Planning — Experienced draftspeople create precise architectural drawings reflecting your priorities. Space is thoughtfully allocated to optimize daily use.
3. Permitting and City Approval — ADU construction in San Jose requires submitting plans to the city's building department for review and approval. Brother & Brother Builders coordinates the permitting on your behalf, responding to review feedback promptly.
4. Excavation and Foundation Installation — Once permits are approved, on-site work kicks off. This includes grading the site, completing foundation work, and establishing utility connections.
5. Shell Construction and Exterior Finishing — Walls and roof systems go up followed by roofing, siding, windows, and exterior doors. At this stage, the ADU takes its visible shape.
6. MEP Systems Rough-In — Certified technicians install the heating, cooling, drainage, and power infrastructure that make the ADU fully functional. Every system is reviewed at each code checkpoint throughout ADU construction.
7. Finishes, Fixtures, and Final Walkthrough — Countertops, hardware, finishes, and fixtures are fitted and completed to the agreed design. A last official inspection confirms the unit is code-compliant and the unit is officially approved for use.

Who Is a Strong Candidate for ADU Construction?

Homeowners who benefit most from ADU construction generally fit within a few recognizable groups. If you own a single-family home with a backyard, garage, or basement that could be converted, you're already in a good starting place. Homeowners looking to generate income through rental are among the most common ADU construction clients, along with families supporting elderly parents.

ADU construction also suits someone who works from home and wants a private work environment that remains away from your family's daily life. Real estate-minded homeowners who are building a portfolio are also prime candidates for ADU construction, since the return on investment is well-documented.

Those who should discuss alternatives first include sites with unusual utility access challenges. Parcels in historic districts or HOA-restricted here communities may need a modified approach. Our experts will evaluate each property individually and honestly to advise you on what's feasible.

ADU Construction FAQ

How long does ADU construction generally take from start to finish?

The full timeline for ADU construction typically ranges from six to fourteen months, depending on design complexity and local permitting timelines. The approval phase alone can take several months in San Jose, so starting early is important. Straightforward interior conversions can move faster, while larger new construction ADUs take longer to complete.

What does ADU construction typically cost?

Costs vary widely based on the type and size of the ADU. For most projects in this region, 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 given after completing a formal feasibility evaluation.

Is ADU construction intrusive while it's underway?

The day-to-day impact depends on where the ADU is being built. Standalone ADU projects are typically less disruptive, since the construction zone is separate. Projects that connect to the main structure may involve some shared wall work during specific stages like framing or MEP rough-in. We provide advance notice about any phases that may affect your routine.

Do I need to leave my home during ADU construction?

In most cases, you are not required to vacate your house during ADU construction. Most builds are designed so that you continue living in the home throughout the process. Certain situations could require a brief departure if significant structural connections require temporary shutoffs in ways that require short-term access disruption. The team at Brother & Brother Builders will discuss these scenarios during the planning phase.

How long will an ADU built through professional ADU construction hold up?

An ADU constructed with quality materials is designed to last as long as the main residence — often several decades with routine maintenance. Durability depends to the standard of construction, whether the unit is properly cared for, and whether systems like roofing and plumbing are serviced regularly. Our builds use residential-grade products rated for longevity and build to current California residential standards to protect your investment for the long haul.

ADU Construction for Local Homeowners

Residential areas across San Jose present a diverse mix of property types that are perfectly suited for ADU construction. Residents in the Rose Garden district frequently see their parcels are well configured for ADU builds. The Berryessa area have seen growing ADU activity as families expand. If you're located closer to Evergreen, our team has likely worked nearby.

San Jose's permitting office follows defined procedures for ADU construction that experienced builders know well. Proximity to transit corridors can influence utility connection requirements for a given ADU project. Our team's knowledge of these local conditions means more accurate timelines and budgets from the first meeting to the final inspection.

Book Your ADU Construction Assessment Today

Should you be thinking about how to add an ADU to your property, Brother & Brother Builders is the team to call. Our experts offer licensed expertise in ADU construction across a wide range of project types — from small attached additions to multi-room backyard residences. Our approach opens with a thorough and honest property review where we understand your vision and give you a realistic picture of what ADU construction on your property will look like.

Contact Brother & Brother Builders to set up your consultation. No matter where you are in the decision-making process, we enjoy discuss timelines, costs, and design possibilities and help you take the next step. 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