Unlock New Space with Quality ADU Construction
Property owners throughout 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 powerful 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 precision and integrity.
The popularity of ADU construction has surged in recent years, and it's easy to understand why. California state law has streamlined permitting for homeowners to add these secondary units, and local municipalities like San Jose have supported the trend as a way to expand the housing supply. Whether you want to build a detached backyard cottage, a garage conversion, or an attached addition, ADU construction gives you more control over how your property serves your household.
At Brother & Brother Builders, we draw on extensive hands-on experience to every ADU construction build. Our team understands the local permitting process, the engineering requirements, and the aesthetic decisions that make an ADU truly livable. When you're ready to explore what ADU construction could do for your property, this guide covers everything you need to here know.
What Is ADU Construction?
ADU construction refers to 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 entryway — that exists on the same lot as a primary residence. ADU construction includes various structural types, including detached backyard units, attached additions, garage conversions, and even interior space reconfigurations.
Mechanically, everything kicks off with a thorough property evaluation, where our professionals evaluate setbacks, zoning, utility access, and structural feasibility. 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 includes foundation work, framing, mechanical systems, weatherproofing, and interior finishing. The result is a move-in-ready living unit adjacent to or detached from your main home.
What separates excellent ADU construction from an average project is the level of craftsmanship at every stage. Components should be specified to match the primary home's aesthetic. Systems like HVAC and drainage must be built for long-term residential demand. Brother & Brother Builders approaches every build with the same high standards 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 increasing appraised value substantially when it's time to sell.
- Monthly Cash Flow — A completed ADU can be rented as a long-term rental or short-term vacation unit, generating steady monthly revenue for the homeowner.
- Space for Loved Ones — ADU construction provides adult children a comfortable home of their own without losing proximity to the family.
- Personalized Layouts — From two-bedroom configurations, ADU construction can be tailored to your household's priorities.
- Streamlined Approval Process — Recent state legislation has minimized the barriers and delays associated with ADU construction, creating a path that is faster and less expensive than ever before.
- Efficient Use of Your Lot — Building an ADU maximizes the land you already own instead of requiring new development, which contributes to sustainability goals.
- Privacy for All Residents — Unlike a bedroom addition, ADU construction creates a truly separate unit where residents have their own space.
- Long-Term Investment Security — A well-built ADU holds its value for many years and generates both livable square footage and monetary benefit.
The ADU Construction Journey Step by Step
- Initial Property Assessment and Feasibility Review — Our builders assess your property to determine what type of ADU is allowed and where it can be placed. This stage clarifies exactly what ADU types will work before any resources go toward planning.
- Blueprint Development and Layout Design — Licensed architects and designers create precise architectural drawings tailored to your needs. Space is thoughtfully allocated to optimize daily use.
- Filing for Building Permits — ADU construction in San Jose demands documentation to the city's building department for sign-off and verification. We manage this entire process on your behalf, resolving any revision requests promptly.
- Excavation and Foundation Installation — Once permits are approved, the build starts. This involves leveling and prepping the ground, pouring the concrete foundation, and setting up utilities.
- Framing, Roofing, and Exterior Work — The structural frame is erected followed by insulation, sheathing, and exterior cladding. During this step, 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 operationally complete. Every system is reviewed at each code checkpoint throughout ADU construction.
- Interior Completion and City Sign-Off — Trim, appliances, tile, and lighting are fitted and completed to the agreed design. A final city 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 typically fall into a few recognizable groups. If you own a single-family home 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 supporting elderly parents.
You may also be someone who runs a small business and wants a private work environment that remains away from your family's daily life. Landlords and real estate investors who want to maximize their land are also prime candidates for ADU construction, since the return on investment is well-documented.
Those who should discuss alternatives first include lots that are below minimum size thresholds. Very small lots or properties with easements may face additional constraints. Brother & Brother Builders reviews each property case by case to recommend the right path forward.
ADU Construction Frequently Asked Questions
How long does ADU construction typically take from start to finish?
The full timeline for ADU construction usually runs between six to fourteen months, depending on design complexity and how quickly approvals come through. City review on its own can take two to four months in San Jose, so planning ahead matters. Simpler garage conversions may complete more quickly, while multi-room detached cottages require more time.
What does ADU construction typically cost?
Costs vary widely based on whether it's a conversion or new construction. For most projects in this region, ADU construction typically ranges from $150,000 to $400,000 or more for a detached new build. Attached ADU additions often come in under, sometimes in the $80,000 to $150,000 range. A detailed estimate can only be given after completing a thorough property review.
Is ADU construction disruptive while it's underway?
How much the build affects daily life depends on where the ADU is being built. Detached backyard builds are generally the least intrusive, since the construction zone is separate. Interior conversions may involve some shared wall work during certain phases of construction. Our team communicates clearly about any phases that may affect your routine.
Do I need to vacate the property during ADU construction?
For the majority of homeowners, you won't have to vacate your primary residence during ADU construction. Most builds are designed so that you stay in your primary unit throughout the process. Certain situations could require a brief departure if major utility upgrades affect the main house in ways that temporarily impact livability. Our project managers will flag these situations during the kickoff meeting.
How long will an ADU built through professional ADU construction hold up?
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 systems installed, how well routine maintenance is performed, and whether systems like roofing and plumbing are serviced regularly. Our builds use high-quality components and build to current California residential standards to protect your investment for the long haul.
ADU Construction for Local Homeowners
The communities throughout San Jose provide a diverse mix of property types that are ideally positioned for ADU construction. Property owners near the Almaden Valley area frequently see their parcels work well for both attached and detached projects. Communities around the Capitol Expressway corridor have seen growing ADU activity as families expand. If you're located closer to Evergreen, our team has likely worked nearby.
The City of San Jose's building department has developed specific protocols for ADU construction that our team navigates routinely. Access to infrastructure along thoroughfares like Monterey Road can impact the design approach for a given ADU project. Brother & Brother Builders' experience across these local conditions means smoother project delivery from kickoff through certificate of occupancy.
Start Your ADU Construction Planning Session Today
Should you be thinking about how to move forward with ADU construction, Brother & Brother Builders is the team to call. Our experts offer years of hands-on experience in ADU construction for many different project types — from small attached additions to multi-room backyard residences. The process begins with a thorough and honest property review where we understand your vision 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. Even if you're just exploring the idea, our team is happy to discuss timelines, costs, and design possibilities 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