Expand Your Home with Quality ADU Construction
Families in San Jose, CA are discovering that adding an accessory dwelling unit is one of the most rewarding investments they can make. ADU construction provides a flexible new living space on your existing property — whether you want to house a family member. Brother & Brother Builders has supported hundreds of local homeowners turn these plans to life with craftsmanship and care.
The demand for ADU construction has surged in recent years, and it's not hard to see 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 expand the housing supply. Whether you're building a detached backyard cottage, a garage conversion, or an attached addition, ADU construction provides increased control over how your property works.
At Brother & Brother Builders, we apply deep 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 beautiful. Should you want to learn about what ADU construction could do for your property, this guide covers everything you need to know.
What Is an ADU Build?
ADU construction describes 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 — including a kitchen, bathroom, sleeping area, and its own entrance — that exists on the same lot as a primary residence. ADU construction can take several forms, including detached backyard units, attached additions, garage conversions, and even basement or interior conversions.
Mechanically, everything kicks off with a thorough property evaluation, where our builders evaluate lot dimensions, existing structures, soil conditions, and local code requirements. From there, design plans are prepared and submitted to the relevant municipal authority. Once the paperwork is cleared, ADU construction transitions to the physical build phase — which covers everything from foundational work, framing, HVAC, drywall, flooring, and exterior finishes. The result is a fully functional 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. Products need to be chosen to complement the existing structure. Systems like HVAC and drainage must be built for long-term residential demand. Brother & Brother Builders approaches every build with the same technical discipline we apply to large-scale custom home projects.
Key Reasons to Choose ADU Construction
- Boosted Home Equity — ADU construction contributes significant market value to your property, often generating strong equity gains when it's time to sell.
- Rental Income Potential — A completed ADU is leasable as a long-term rental or short-term vacation unit, creating ongoing passive income for the homeowner.
- Housing for Extended Family — ADU construction gives aging parents a comfortable home of their own without losing proximity to the family.
- Customization Options — From open-plan one-bedrooms, ADU construction is adaptable to your specific needs.
- Streamlined Approval Process — Recent state legislation has cut down the permitting obstacles associated with ADU construction, creating a path that is faster and more affordable than ever before.
- Responsible Property Development — Building an ADU works within your current footprint instead of consuming open land, which supports broader sustainability goals.
- Separate Entrances and Spaces — Unlike a bedroom addition, ADU construction produces a fully self-contained unit where occupants have full privacy.
- Lasting Financial Benefit — A well-built ADU remains an asset for decades, providing both functional space and financial upside.
The ADU Construction Journey Step by Step
- Site Evaluation and Zoning Analysis — Our builders assess your property to evaluate setbacks, lot coverage limits, and utility connections. This phase answers exactly what can be built before any resources go toward planning.
- Blueprint Development and Layout Design — Our design team create precise architectural drawings tailored to your needs. Layouts are carefully considered to optimize daily use.
- Filing for Building Permits — ADU construction in San Jose requires submitting plans to the city's building department for inspection and clearance. We manage this entire process on your behalf, addressing any city comments promptly.
- Site Preparation and Foundation Work — Once permits are issued, on-site work kicks off. This involves leveling and prepping the ground, completing foundation work, and running initial plumbing and electrical conduits.
- Framing, Roofing, and Exterior Work — Framing is completed followed by roofing, siding, windows, and exterior doors. At this stage, the ADU becomes recognizable as a structure.
- MEP Systems Rough-In — Skilled tradespeople install the heating, cooling, drainage, and power infrastructure that make the ADU ready for occupancy. All work is inspected at required milestones throughout ADU construction.
- Interior Finishing and Final Inspections — Trim, appliances, tile, and lighting are installed and finished to your specifications. A closing municipal review confirms the unit is code-compliant and the ADU is ready for use.
Who Is a Strong Candidate for ADU Construction?
People who see the greatest return from ADU construction typically fall into a few clear categories. If you have a residential property with available square footage under zoning rules, you're already in a good starting place. Homeowners hoping to offset mortgage costs through rental are among the most common ADU construction clients, along with families navigating multigenerational living situations.
Another strong candidate is someone who runs a small business and wants a detached creative or business space that remains away from your family's daily life. Property investors and rental owners who are building a portfolio are also well suited for ADU construction, since the long-term value is proven.
Homeowners who may want to pause and evaluate include properties with significant setback limitations. Very small lots or properties with easements may require additional review. Our experts will evaluate each property case by case to provide realistic options.
ADU Construction Frequently Asked Questions
How long does ADU construction typically take from start to finish?
The total process for ADU construction usually runs between six to fourteen months, influenced by the type of unit being built 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. Simpler garage conversions can move faster, 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. In the San Jose area, ADU construction typically ranges from $150,000 to $400,000 or more for a detached new build. Attached ADU additions are generally priced lower, sometimes between $75,000 and $140,000. A detailed estimate can only be developed after a thorough property review.
Is ADU construction difficult to live through while it's underway?
The day-to-day impact depends on where the ADU is being built. Detached backyard builds are typically less disruptive, since the crew operates at a distance from your living areas. Garage conversions or attached additions may require temporary access during key milestones. Brother & Brother Builders keeps you informed about upcoming work and timelines.
Do I need to vacate the property during ADU construction?
In most cases, you do not need to vacate your house during ADU construction. The vast majority of projects are set up to let you stay in your primary unit throughout the process. Exceptions may arise if major utility upgrades affect the main house in ways that briefly affect habitability. The team at Brother & Brother Builders 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?
An ADU constructed with quality materials should last as long as any standard residential structure — typically 50 years or more. Durability depends to the standard of construction, how consistently minor repairs are addressed, and how proactively issues are resolved over time. Brother & Brother Builders specifies residential-grade products rated for longevity and follow all code requirements to protect your investment for the long haul.
ADU Construction for San Jose Homeowners
San Jose's neighborhoods offer a variety of property types that are well suited for ADU construction. Residents in the Rose Garden district often discover their properties work well for both attached and detached projects. The Berryessa area are increasingly popular for ADU construction as multigenerational living becomes more common. If you're located closer to Evergreen, our team has likely worked nearby.
San Jose's permitting office applies particular standards for ADU construction that experienced builders know well. Location near major arterials like Story Road or Tully Road can impact the design approach for a given ADU project. Our familiarity with these local conditions means fewer surprises from the first meeting to the final inspection.
Start Your ADU Construction Planning Session Today
When you want to add an ADU to your property, Brother & Brother Builders is ready to guide you. Our builders provide years of hands-on experience in ADU construction including all types of project types — from small attached additions to fully independent secondary homes. Our approach opens with a thorough and honest property review where we listen to your goals and share clear expectations of what's achievable.
Contact Brother & Brother Builders to schedule a site visit. 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. This type of project is a meaningful commitment — and we're committed to helping you get it right.
Brother & Brother Builders | Brother & Brother Builders adu construction 3109 Stevens Creek Boulevard | San Jose CA 95117 | (888) 412-2632