Expand Your Home with Professional ADU Construction
Homeowners across San Jose, CA are discovering that adding an accessory dwelling unit is one of the most practical investments they can make. ADU construction provides 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 bring these projects to life with precision and transparency.
The interest in ADU construction has grown rapidly in recent years, and it's easy to understand why. California state law has streamlined permitting for homeowners to build these secondary units, and local municipalities like San Jose have supported 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 provides increased control over how your property works.
At Brother & Brother Builders, we draw on extensive hands-on experience to every ADU construction build. Our team is familiar with city and county requirements, the engineering considerations, and the aesthetic decisions that make an ADU truly livable. If you've been thinking about what ADU construction could mean for your property, this guide covers everything you need to know.
What Is ADU Construction?
ADU construction refers to 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 — featuring a kitchen, bathroom, sleeping area, and its own entrance — that sits on the same property 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 team evaluate setbacks, zoning, utility access, and structural feasibility. From there, blueprints are prepared and submitted to the local building department. 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 completely finished living unit attached to or separate from your main home.
What separates excellent ADU construction from an average project is the depth of planning at every stage. Materials must be selected to complement the existing structure. Systems like plumbing and electrical must be designed to handle full-time occupancy. Brother & Brother Builders approaches every build with the same high standards we bring to full custom home projects.
Key Reasons to Choose ADU Construction
- Increased Property Value — ADU construction delivers real 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, providing a consistent income stream for the homeowner.
- Housing for Extended Family — ADU construction offers family members a self-contained residence without losing proximity to the family.
- Personalized Layouts — From two-bedroom configurations, ADU construction may be customized to your specific needs.
- Faster Permitting in California — Recent state legislation has reduced the permitting obstacles associated with ADU construction, resulting in a timeline that is faster and more affordable than ever before.
- Responsible Property Development — Building an ADU maximizes the land you already own instead of requiring new development, which aligns with 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 livable square footage and monetary benefit.
The ADU Construction Procedure Step by Step
- Initial Property Assessment and Feasibility Review — Our team visits your property to evaluate setbacks, lot coverage limits, and utility connections. This phase answers exactly what's possible before any time is invested in drawings.
- Blueprint Development and Layout Design — Experienced draftspeople create precise architectural drawings based on your goals. Space is thoughtfully allocated to maximize function and livability.
- Permitting and City Approval — ADU construction in San Jose involves filing drawings to the city's building department for inspection and clearance. Brother & Brother Builders coordinates the permitting on your behalf, responding to review feedback promptly.
- Excavation and Foundation Installation — Once permits are approved, physical construction begins. This covers land preparation, pouring the concrete foundation, and establishing utility connections.
- Structural Framing and Weatherproofing — Walls and roof systems go up followed by roofing, siding, windows, and exterior doors. This phase, the ADU transforms from a concept to a building.
- Interior Systems and Infrastructure — Licensed subcontractors install the water supply, drain lines, and electrical panel that make the ADU fully functional. All work is inspected at required milestones throughout ADU construction.
- Interior Finishing and Final Inspections — Trim, appliances, tile, and lighting are placed and inspected to the approved plan. A last official inspection confirms the unit is code-compliant and the unit is officially approved for use.
Who Is a Good Candidate for ADU Construction?
People who see the greatest return 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 in a good starting place. Homeowners hoping to offset mortgage costs through rental are among the most motivated 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 doesn't interfere with your family's daily life. Property investors and rental owners who already own residential properties are also a natural fit for ADU construction, since the return on investment is well-documented.
Situations where ADU construction may not be the best first step include lots that are below minimum size thresholds. Very small lots or properties with easements may need a modified approach. Brother & Brother Builders reviews each property case by case to recommend the right path forward.
ADU Construction Common Questions Answered
How long does ADU construction usually take from start to finish?
The complete duration for ADU construction commonly spans six to fourteen months, depending on design complexity and how quickly approvals come through. Permitting alone can take several months in San Jose, so planning ahead matters. Simpler garage conversions may complete more quickly, while multi-room detached cottages take longer to complete.
What does ADU construction typically cost?
Budget requirements differ based on whether it's a conversion or new construction. In the San Jose area, ADU construction generally falls between $150,000 to $400,000 or more for a standalone backyard unit. Garage conversions often come in under, sometimes between $75,000 and $140,000. A precise cost projection can only be given after completing a full site assessment.
Is ADU construction intrusive while it's underway?
The day-to-day impact depends on the project's location on your property. New construction in the read more rear yard are generally the least intrusive, since the crew operates at a distance from your living areas. Interior conversions may require temporary access during certain phases of construction. Our team communicates clearly about what to expect at each stage.
Do I need to move out during ADU construction?
Generally speaking, you do not need to vacate your main home during ADU construction. The vast majority of projects are designed so that you continue living in the home throughout the process. Certain situations could require a brief departure if major utility upgrades affect the main house in ways that require short-term access disruption. Our project managers will walk you through any potential disruptions during the planning phase.
How long will an ADU built through professional ADU construction hold up?
A well-built ADU should last as long as the main residence — typically 50 years or more. Durability depends to the quality of materials used, how well routine maintenance is performed, and if mechanical components are maintained on schedule. We select high-quality components 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 diverse mix of property types that are perfectly suited for ADU construction. Homeowners in the Willow Glen neighborhood frequently see their parcels accommodate detached backyard units nicely. 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 has project experience in the area.
Local regulatory bodies in this area has developed specific protocols 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 team's knowledge of the San Jose permitting environment means more accurate timelines and budgets from design through the final walkthrough.
Book Your ADU Construction Planning Session Today
If you're ready to move forward with ADU construction, Brother & Brother Builders is here to help. We bring proven skills in ADU construction for many different project types — from modest studio builds to fully independent secondary homes. The process begins with a detailed, no-pressure consultation where we listen to your goals and share clear expectations of what's achievable.
Contact Brother & Brother Builders to begin the conversation. Whether you're in the early stages of planning, our team is happy to walk through your options, review completed projects 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 | 3109 Stevens Creek Boulevard | San Jose CA 95117 | (888) 412-2632