Unlock New Space with Quality ADU Construction
Homeowners across San Jose, more info CA are finding that adding an accessory dwelling unit is one of the most practical investments they can make. ADU construction creates a flexible new living space on your existing property — whether you want to house a family member. Brother & Brother Builders has guided hundreds of local homeowners turn these plans to life with precision and transparency.
The interest in ADU construction has increased significantly in recent years, and it's easy to understand why. California state law has simplified the process for homeowners to build these secondary units, and local municipalities like San Jose have supported 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 requirements, and the planning steps that make an ADU beautiful. If you've been thinking about what ADU construction could look like on your property, this guide explains everything you need to know.
What Is the ADU Construction Process?
ADU construction refers to the process of designing, permitting, and building an accessory dwelling unit on a residential property. An accessory dwelling unit is a self-contained living space — featuring a kitchen, bathroom, sleeping area, and its own entrance — that sits on the same property as a primary residence. ADU construction includes various structural types, including detached backyard units, attached additions, garage conversions, and even interior space reconfigurations.
Mechanically, the process begins with a detailed site assessment, where our team evaluate property boundaries, available square footage, and infrastructure capacity. From there, design plans are prepared and submitted to the relevant municipal authority. Once the paperwork is cleared, 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 adjacent to or detached from 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 wiring and water supply 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
- Increased Property Value — ADU construction contributes significant market value to your property, often returning more than the build cost when it's time to sell.
- Revenue Generation — A completed ADU is leasable as a long-term rental or short-term vacation unit, creating ongoing passive income for the homeowner.
- Space for Loved Ones — ADU construction offers family members a private, independent living space without moving to another neighborhood.
- Design Flexibility — From modern studio layouts, ADU construction may be customized to your specific needs.
- Streamlined Approval Process — Recent state legislation has cut down the red tape associated with ADU construction, making the process that is faster and more cost-efficient than ever before.
- Responsible Property Development — Building an ADU maximizes the land you already own instead of expanding urban sprawl, which contributes to sustainability goals.
- Privacy for All Residents — Unlike a bedroom addition, ADU construction produces a fully self-contained unit where occupants have full privacy.
- Long-Term Investment Security — A well-built ADU continues to produce returns for the long haul by offering both usable housing and equity growth.
The ADU Construction Process Step by Step
- Property Walkthrough and Feasibility Check — Our builders assess your property to evaluate setbacks, lot coverage limits, and utility connections. This step tells you exactly what can be built before any money is spent on design.
- Architectural Drafting and Space Planning — Our design team create comprehensive blueprints reflecting your priorities. Space is thoughtfully allocated to maximize function and livability.
- Permit Submission and Municipal Review — ADU construction in San Jose requires submitting plans to the city's building department for sign-off and verification. Our team handles all submissions on your behalf, addressing any city comments promptly.
- Excavation and Foundation Installation — Once permits are issued, the build starts. This covers land preparation, completing foundation work, and establishing utility connections.
- Structural Framing and Weatherproofing — Framing is completed followed by weatherproofing and exterior finish materials. This phase, the ADU transforms from a concept to a building.
- MEP Systems Rough-In — Licensed subcontractors install the heating, cooling, drainage, and power infrastructure that make the ADU ready for occupancy. Inspections are completed at each code checkpoint throughout ADU construction.
- Finishes, Fixtures, and Final Walkthrough — Trim, appliances, tile, and lighting are placed and inspected to the agreed design. A final city inspection issues the certificate of occupancy and the unit is officially approved for use.
Who Is a Strong Candidate for ADU Construction?
People who see the greatest return from ADU construction generally fit within a few common profiles. If you own a single-family home 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 accommodating adult children who need housing.
You may also be 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 already own residential properties are also well suited for ADU construction, since the return on investment is well-documented.
Those who should discuss alternatives first include sites with unusual utility access challenges. Parcels in historic districts or HOA-restricted communities may require additional review. 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 typically ranges from six to fourteen months, influenced by the type of unit being built and local permitting timelines. The approval phase alone can take a significant portion of the overall timeline in San Jose, so starting early is important. Straightforward interior conversions can move faster, while larger new construction ADUs fall toward the upper end of the timeline.
What does ADU construction typically cost?
Pricing depends on many factors based on project complexity and finishes selected. For most projects in this region, ADU construction typically ranges from $150,000 to $400,000 or more for a standalone backyard unit. Attached ADU additions tend to cost less, sometimes in the $80,000 to $150,000 range. An accurate budget can only be developed after a full site assessment.
Is ADU construction disruptive while it's underway?
How much the build affects daily life depends on the project's location on your property. Standalone ADU projects are typically less disruptive, since work happens away from the main house. Interior conversions may require temporary access during specific stages like framing or MEP rough-in. Brother & Brother Builders keeps you informed about upcoming work and timelines.
Do I need to move out during ADU construction?
In most cases, you won't have to vacate your primary residence during ADU construction. The vast majority of projects are structured to allow you stay in your primary unit throughout the construction timeline. There are edge cases if interior conversion work touches shared systems in ways that temporarily impact livability. Our construction supervisors will flag these situations 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 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 residential-grade products rated for longevity and comply with all local building codes to ensure lasting performance.
ADU Construction for Local Homeowners
Residential areas across San Jose present a wide range of property types that are well suited for ADU construction. Property owners near the Almaden Valley area have found their lots accommodate detached backyard units nicely. Communities around the Capitol Expressway corridor 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 has likely worked nearby.
San Jose's permitting office follows defined procedures for ADU construction that require a builder familiar with local expectations. Location near major arterials like Story Road or Tully Road can influence utility connection requirements for a given ADU project. Brother & Brother Builders' experience across this region's building landscape means more accurate timelines and budgets from design through the final walkthrough.
Schedule Your ADU Construction Planning Session Today
When you want to add an ADU to your property, Brother & Brother Builders is here to help. We bring proven skills in ADU construction across a wide range of project types — from small attached additions to multi-room backyard residences. The process begins with a comprehensive site assessment where we listen to your goals and give you a realistic picture of what's achievable.
Get in touch with our office to set up your consultation. No matter where you are in the decision-making process, our team is happy to discuss timelines, costs, and design possibilities and make sure you feel confident before committing. ADU construction is a significant investment — and our goal is to ensure it delivers real value.
Brother & Brother Builders | 3109 Stevens Creek Boulevard | San Jose CA 95117 | (888) 412-2632