Unlock New Space with Professional 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 creates a flexible new living space on your existing property — whether you want to create a private workspace. Brother & Brother Builders has supported hundreds of local homeowners bring these projects to life with skill and care.
The popularity of ADU construction has surged in recent years, and it's not hard to see why. California state law now makes it easier for homeowners to add these secondary units, and local municipalities like San Jose have encouraged 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 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 build. Our team understands the local permitting process, the engineering considerations, and the design choices that make an ADU truly livable. If you've been thinking about what ADU construction could look like on your property, this guide will walk you through everything you need to know.
What Is ADU Construction?
ADU construction involves 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 — including a kitchen, bathroom, sleeping area, and its own entryway — 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 interior space reconfigurations.
Mechanically, the work starts with a detailed site assessment, 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 approvals are in place, ADU construction enters the physical build phase — which encompasses site preparation, framing, mechanical systems, weatherproofing, and interior finishing. The result is a fully functional living unit attached to or separate from your main home.
The difference between a good and a great ADU build is the attention to detail at every stage. Materials must be selected 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 apply to large-scale custom home projects.
Key Advantages ADU Construction
- Boosted Home Equity — ADU construction adds measurable market value to your property, often increasing appraised value substantially when it's time to sell.
- Monthly Cash Flow — A completed ADU is leasable as a long-term rental or short-term vacation unit, providing a consistent income stream for the homeowner.
- Multi-Generational Living — ADU construction offers family members a private, independent living space without leaving the property.
- Personalized Layouts — From two-bedroom configurations, ADU construction is adaptable to the intended occupant's lifestyle.
- Faster Permitting in California — Recent state legislation has minimized the permitting obstacles 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 consuming open land, which supports broader sustainability goals.
- Independent Living Areas — Unlike a bedroom addition, ADU construction creates a truly separate unit where tenants live autonomously.
- Long-Term Investment Security — A well-built ADU remains an asset for the long haul by offering both usable housing and equity growth.
The ADU Construction Journey Step by Step
- 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 step tells you exactly what can be built before any money is spent on design.
- Custom Design and Architectural Planning — Licensed architects and designers create detailed floor plans reflecting your priorities. Layouts are carefully considered to optimize daily use.
- Filing for Building Permits — ADU construction in San Jose involves filing drawings to the city's building department for inspection and clearance. We manage this entire process on your behalf, resolving any revision requests promptly.
- Excavation and Foundation Installation — Once permits are issued, on-site work kicks off. This involves leveling and prepping the ground, pouring the concrete foundation, and setting up utilities.
- Framing, Roofing, and Exterior Work — Walls and roof systems go up followed by insulation, sheathing, and exterior cladding. At this stage, 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 operationally complete. Inspections are completed at each code checkpoint throughout ADU construction.
- Finishes, Fixtures, and Final Walkthrough — Flooring, cabinetry, fixtures, paint are installed and finished to the approved plan. A closing municipal review grants legal occupancy status and the ADU is ready for use.
Who Is a Good Candidate for ADU Construction?
Property owners who are best suited from ADU construction often belong to a few common profiles. If you have a residential property with enough lot space to meet setback requirements, you're already a strong candidate. Homeowners looking to generate income 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 needs a dedicated professional workspace and wants a separate office or studio space that doesn't interfere with your family's daily life. Real estate-minded homeowners who already own residential properties are also well suited 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. Parcels in historic districts or HOA-restricted communities 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 generally take from start to finish?
The complete duration for ADU construction commonly spans six to fourteen months, based on the project scope and local permitting timelines. City review on its own can take several months in San Jose, so beginning the process sooner rather than later is wise. Simpler garage conversions may complete more quickly, while custom detached builds require more time.
What does ADU construction usually run in terms of budget?
Pricing depends on many factors based on whether it's a conversion or new construction. Locally, ADU construction generally falls between $150,000 to $400,000 or more for a fully custom construction. Garage conversions tend to cost less, sometimes between $75,000 and $140,000. A precise cost projection can only be developed after a thorough property review.
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 work happens away from the main house. Garage conversions or attached additions may require temporary access during key milestones. 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 won't have to vacate your main home during ADU construction. Most builds are structured to allow you remain on the property throughout the process. There are edge cases if major utility upgrades affect the main house in ways that temporarily impact livability. The team at Brother & Brother Builders will walk you through any potential disruptions during the kickoff meeting.
How long will an ADU built through professional ADU construction last?
Any ADU built to code with professional oversight is designed to last as long as the main residence — often several decades with routine maintenance. Durability depends to the standard of construction, how well routine maintenance is performed, and how proactively issues are resolved over time. Our builds use high-quality components and build to current California residential standards 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. Residents in the Rose Garden district often discover their properties work well for both attached and detached projects. Neighborhoods near Blossom Hill Road are seeing more homeowners add secondary units as multigenerational living becomes more common. 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 experienced builders know well. 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 smoother project delivery from design through the final read more walkthrough.
Schedule Your ADU Construction Planning Session Today
If you're ready to move forward with ADU construction, 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 modest studio builds to fully independent secondary homes. Every project starts with a thorough and honest property review where we learn what you're trying to accomplish and provide an honest assessment of what the project will involve.
Contact Brother & Brother Builders to begin the conversation. No matter where you are in the decision-making process, we enjoy walk through your options, review completed projects and help you take the next step. 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