Brother & Brother Builders

Transform Your Property with Quality ADU Construction

Homeowners across 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 versatile new living space on your existing property — whether you want to house a family member. Brother & Brother Builders has guided hundreds of local homeowners turn these plans to life with precision and transparency.

The demand for ADU construction has surged in recent years, and it's no mystery. California state law has simplified the process for homeowners to construct these secondary units, and local municipalities like San Jose have encouraged 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 offers greater control over how your property serves your household.

At Brother & Brother Builders, we apply deep hands-on experience to every ADU construction job. Our team is familiar with city and county requirements, the engineering details, and the planning steps that make an ADU beautiful. If you've been thinking about 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 refers to the process of designing, permitting, and building an accessory dwelling unit on a residential property. An accessory dwelling unit is a fully independent living space — equipped with a kitchen, bathroom, sleeping area, and its own access point — that is located on the same parcel as a primary residence. ADU construction includes various structural types, including detached backyard units, attached additions, garage conversions, and even below-grade dwelling units.

Mechanically, the process begins with a comprehensive review of your lot, where our professionals evaluate property boundaries, available square footage, and infrastructure capacity. From there, architectural drawings are prepared and submitted to the relevant municipal authority. Once the paperwork is cleared, ADU construction enters the physical build phase — which covers everything from foundational work, framing, HVAC, drywall, flooring, and exterior finishes. The result is a completely finished living unit attached to or separate from your main home.

The difference between a good and a great ADU build is the level of craftsmanship at every stage. Materials must be selected to align with the neighborhood's character. Systems like plumbing and electrical must be built for long-term residential demand. Brother & Brother Builders treats each project with the same professional rigor we apply to large-scale custom home projects.

Key Benefits ADU Construction

• Boosted Home Equity — ADU construction adds measurable 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, generating steady monthly revenue for the homeowner.
• Housing for Extended Family — ADU construction gives aging parents a self-contained residence without losing proximity to the family.
• Customization Options — From open-plan one-bedrooms, ADU construction may be customized to your specific needs.
• Faster Permitting in California — Recent state legislation has reduced the red tape associated with ADU construction, creating a path 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.
• Privacy for All Residents — Unlike a bedroom addition, ADU construction creates a truly separate unit where occupants have full privacy.
• Lasting Financial Benefit — A well-built ADU holds its value for decades, providing both livable square footage and monetary benefit.

The ADU Construction Process Step by Step

1. Property Walkthrough and Feasibility Check — Our experts review your property to analyze zoning rules, slope conditions, and available square footage. This stage clarifies exactly what's possible before any money is spent on design.
2. Blueprint Development and Layout Design — Experienced draftspeople create precise architectural drawings tailored to your needs. Layouts are carefully considered to maximize function and livability.
3. Permitting and City Approval — ADU construction in San Jose requires submitting plans to the city's building department for sign-off and verification. Brother & Brother Builders coordinates the permitting on your behalf, responding to review feedback promptly.
4. Ground Prep and Structural Base — Once permits are approved, physical construction begins. This includes grading the site, laying the structural base, and running initial plumbing and electrical conduits.
5. Shell Construction and Exterior Finishing — The structural frame is erected followed by weatherproofing and exterior finish materials. At this stage, the ADU becomes recognizable as a structure.
6. Mechanical, Electrical, and Plumbing Installation — Certified technicians install the heating, cooling, drainage, and power infrastructure that make the ADU ready for occupancy. Inspections are completed at required milestones throughout ADU construction.
7. Interior Completion and City Sign-Off — Flooring, cabinetry, fixtures, paint are placed and inspected to the agreed design. A last official inspection confirms the unit is code-compliant and the ADU is ready for use.

Who Is a Right Fit for ADU Construction?

Homeowners who benefit most from ADU construction often belong to a few common profiles. If you are a homeowner with a backyard, garage, or basement that could be converted, you're already a strong candidate. Homeowners hoping to offset mortgage costs through rental are among the most common ADU construction clients, along with families accommodating adult children who need housing.

Another strong candidate is someone who runs a small business and wants a private work environment that is distinct from your family's daily life. Real estate-minded homeowners who already own residential properties are also well suited for ADU construction, since the long-term value is proven.

Those who should discuss alternatives first include lots that are below minimum size thresholds. Sites with underground infrastructure conflicts 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 complete duration for ADU construction usually runs between six to fourteen months, influenced by the type of unit being built and local permitting timelines. Permitting alone can take a significant portion of the overall timeline in San Jose, so beginning the process sooner rather than later is wise. Smaller detached units often finish in the lower end of the range, while multi-room detached cottages take longer to complete.

What does ADU construction cost in San Jose?

Budget requirements differ based on the type and size of the ADU. Locally, ADU construction typically ranges from $150,000 to $400,000 or more for a standalone backyard unit. Interior conversion projects often come in under, sometimes starting around $80,000 depending on scope. A detailed estimate can only be produced following a formal feasibility evaluation.

Is ADU construction intrusive while it's underway?

The level of disruption depends on whether you're converting existing space or building new. New construction in the rear yard are usually easier to live alongside, since the crew operates at a distance from your living areas. Garage conversions or attached additions 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 vacate the property during ADU construction?

In most cases, you won't have to vacate your main home during ADU construction. Most job sites are designed so that you stay in more info your primary unit throughout the construction timeline. There are edge cases if major utility upgrades affect the main house in ways that require short-term access disruption. The team at Brother & Brother Builders will flag these situations during the pre-construction consultation.

How long will an ADU built through professional ADU construction remain in good condition?

A well-built ADU is designed to last as long as any standard residential structure — often several decades with routine maintenance. Longevity is tied to the quality of materials used, whether the unit is properly cared for, and if mechanical components are maintained on schedule. Our builds use high-quality components and comply with all local building codes to ensure lasting performance.

ADU Construction for Local Homeowners

The communities throughout San Jose provide a variety of property types that are perfectly suited for ADU construction. Property owners near the Almaden Valley area have found their lots work well for both attached and detached projects. Communities around the Capitol Expressway corridor are seeing more homeowners add secondary units as housing demand rises. If you're located closer to Evergreen, our team knows the permitting landscape well.

The City of San Jose's building department follows defined procedures for ADU construction that our team navigates routinely. Proximity to transit corridors can affect how quickly permits are approved for a given ADU project. Brother & Brother Builders' experience across this region's building landscape means fewer surprises from the first meeting to the final inspection.

Schedule 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. We bring licensed expertise in ADU construction for many different project types — from simple garage conversions to multi-room backyard residences. The process begins with a comprehensive site assessment where we learn what you're trying to accomplish and provide an honest assessment of what the project will involve.

Get in touch with our office to schedule a site visit. Even if you're just exploring the idea, our team is happy to answer questions, share examples of our work and give you the clarity you need to move forward. ADU construction is a significant investment — and we're committed to helping you get it right.

Brother & Brother Builders | 3109 Stevens Creek Boulevard | San Jose CA 95117 | (888) 412-2632