Expand Your Home with Professional ADU Construction
Property owners throughout San Jose, CA are realizing that adding an accessory dwelling unit is one of the smartest 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 helped hundreds of local homeowners see these visions to life with precision and integrity.
The popularity of ADU construction has increased significantly in recent years, and it's not hard to see why. California state law has streamlined permitting for homeowners to add 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 works.
At Brother & Brother Builders, we draw on extensive hands-on experience to every ADU construction job. Our team knows the San Jose building codes, the engineering details, and the aesthetic decisions that make an ADU functional. If you've been thinking about what ADU construction could do for 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 complete living space — including a kitchen, bathroom, sleeping area, and its own entryway — 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 below-grade dwelling units.
Mechanically, the process begins with a detailed site assessment, where our professionals evaluate lot dimensions, existing structures, soil conditions, and local code requirements. From there, blueprints 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 completely finished living unit connected to or independent of your main home.
What sets quality ADU construction apart is the attention to detail at every stage. Products need to be chosen to complement the existing structure. Systems like wiring and water supply must be sized for independent daily use. Brother & Brother Builders treats each project with the same high standards we bring to full custom home projects.
Key Reasons to Choose ADU Construction
- Increased Property Value — ADU construction contributes significant market value to your property, often increasing appraised value substantially 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.
- Multi-Generational Living — ADU construction offers family members a comfortable home of their own without losing proximity to the family.
- Design Flexibility — From two-bedroom configurations, ADU construction may be customized to the intended occupant's lifestyle.
- Simplified Regulatory Path — Recent state legislation has cut down the red tape associated with ADU construction, resulting in a timeline 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 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 tenants live autonomously.
- Durable Return on Investment — A well-built ADU remains an asset for decades, providing both usable housing and equity growth.
The ADU Construction Procedure Step by Step
- Property Walkthrough and Feasibility Check — Our team visits your property to determine what type of ADU is allowed and where it can be placed. This phase answers exactly what's possible before any resources go toward planning.
- Custom Design and Architectural Planning — Licensed architects and designers create detailed floor plans reflecting your priorities. Layouts are carefully considered to optimize daily use.
- Permitting and City Approval — ADU construction in San Jose involves filing drawings to the city's building department for sign-off and verification. We manage this entire process on your behalf, addressing any city comments promptly.
- Site Preparation and Foundation Work — Once permits are issued, the build starts. This involves leveling and prepping the ground, laying the structural base, and running initial plumbing and electrical conduits.
- Framing, Roofing, and Exterior Work — Framing is completed followed by insulation, sheathing, and exterior cladding. At this stage, the ADU takes its visible shape.
- Mechanical, Electrical, and Plumbing Installation — Licensed subcontractors install the heating, cooling, drainage, and power infrastructure that make the ADU fully functional. All work is inspected at each code checkpoint throughout ADU construction.
- Interior Finishing and Final Inspections — Trim, appliances, tile, and lighting are fitted and completed to your specifications. A final city inspection issues the certificate of occupancy and the unit is officially approved 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 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 common ADU construction clients, along with families navigating multigenerational living situations.
You may also be someone who works from home 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.
Homeowners who may want to pause and evaluate include sites with unusual utility access challenges. Sites with underground infrastructure conflicts may need a modified approach. Brother & Brother Builders reviews each property individually and honestly to provide realistic options.
ADU Construction Frequently Asked Questions
How long does ADU construction generally take from start to finish?
The full timeline for ADU construction usually runs between six to fourteen months, influenced by the type of unit being built and city review schedules. Permitting alone can take a significant portion of the overall timeline in San Jose, so starting early is important. Straightforward interior conversions may complete more quickly, while multi-room detached cottages fall toward the upper end of the timeline.
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 commonly costs $150,000 to $400,000 or more for a detached new build. Garage conversions are generally priced lower, sometimes in the $80,000 to $150,000 range. A detailed estimate can only be developed after a full site assessment.
Is ADU construction disruptive while it's underway?
The level of disruption depends on the project's location on your property. New construction in the rear yard are usually easier to live alongside, since the construction zone is separate. Interior conversions may require temporary access during specific stages like framing or MEP rough-in. Our team communicates clearly about any phases that may affect your routine.
Do I need to move out during ADU construction?
In most cases, you won't have to vacate your main home during ADU construction. Most job sites are structured to allow 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 construction supervisors will walk you through any potential disruptions during the kickoff meeting.
How long will an ADU built through professional ADU construction last?
An ADU constructed with quality materials can be expected to last as long as the main residence — typically 50 years or more. Durability depends to the systems installed, how well routine maintenance is performed, and whether systems like roofing and plumbing are serviced regularly. We select commercial-grade materials and comply with all local building codes to protect your investment for the long haul.
ADU Construction for Local Homeowners
Residential areas across San Jose present a wide range of property types that are ideally positioned for ADU construction. Residents in the Rose Garden district often discover their properties are well configured for ADU builds. Communities around the Capitol Expressway corridor have seen growing ADU activity as multigenerational living becomes more common. If you're located closer to Evergreen, our team has likely worked nearby.
Local regulatory bodies in this area follows defined procedures 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 fewer surprises from the first meeting to the final inspection.
Book Your ADU Construction Assessment Today
Should you be thinking about how to move forward with ADU construction, Brother & Brother Builders is here to help. We bring licensed expertise in ADU construction across a wide range of project types — from small attached additions to fully independent secondary homes. The process begins with a comprehensive site assessment where we listen to get more info your goals and share clear expectations of what's achievable.
Contact Brother & Brother Builders to set up your consultation. No matter where you are in the decision-making process, our team is happy to answer questions, share examples of our work and help you take the next step. 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