Expand Your Home with Professional ADU Construction
Homeowners across San Jose, CA are discovering that adding an accessory dwelling unit is one of the smartest investments they can make. ADU construction opens the door to a versatile new living space on your existing property — whether you want to create a private workspace. 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 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. Whether you want to build 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 bring years of hands-on experience to every ADU construction job. Our team understands the local permitting process, the engineering details, and the aesthetic decisions 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 an ADU Build?
ADU construction involves 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 comes in multiple configurations, including detached backyard units, attached additions, garage conversions, and even interior space reconfigurations.
Mechanically, the work starts with a comprehensive review of your lot, where our professionals evaluate property boundaries, available square footage, and infrastructure capacity. From there, design plans are prepared and submitted to the local building department. Once permits are secured, ADU construction moves into the physical build phase — which covers everything from foundational work, framing, mechanical systems, weatherproofing, and interior finishing. The result is a fully functional living unit attached to or separate from your main home.
What sets quality ADU construction apart is the level of craftsmanship at every stage. Products need to be chosen to align with the neighborhood's character. Systems like HVAC and drainage must be designed to handle full-time occupancy. Brother & Brother Builders treats each project with the same professional rigor we use on major custom home projects.
Key Benefits ADU Construction
- Higher Resale Potential — ADU construction delivers real market value to your property, often generating strong equity gains when it's time to sell.
- Rental Income Potential — A completed ADU may be listed as a long-term rental or short-term vacation unit, creating ongoing passive income for the homeowner.
- Multi-Generational Living — ADU construction provides adult children a self-contained residence without moving to another neighborhood.
- Customization Options — From open-plan one-bedrooms, 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, resulting in a timeline that is faster and more affordable than ever before.
- Sustainable Land Use — Building an ADU works within your current footprint instead of expanding urban sprawl, which aligns with sustainability goals.
- Privacy for All Residents — Unlike a bedroom addition, ADU construction creates a truly separate unit where occupants have full privacy.
- Durable Return on Investment — A well-built ADU holds its value for decades, providing both functional space and financial upside.
The ADU Construction Journey Step by Step
- Site Evaluation and Zoning Analysis — Our team visits your property to determine what type of ADU is allowed and where it can be placed. This phase answers exactly what ADU types will work before any resources go toward planning.
- Blueprint Development and Layout Design — Our design team create comprehensive blueprints based on your goals. Layouts are carefully considered to maximize function and livability.
- Filing for Building Permits — ADU construction in San Jose requires submitting plans to the city's building department for review and approval. Our team handles all submissions on your behalf, addressing any city comments promptly.
- Site Preparation and Foundation Work — Once permits are issued, physical construction begins. This covers land preparation, laying the structural base, and running initial plumbing and electrical conduits.
- Framing, Roofing, and Exterior Work — Walls and roof systems go up followed by roofing, siding, windows, and exterior doors. This phase, the ADU takes its visible shape.
- Interior Systems and Infrastructure — Skilled tradespeople install the water supply, drain lines, and electrical panel that make the ADU ready for occupancy. All work is inspected at designated stages throughout ADU construction.
- Interior Completion and City Sign-Off — Trim, appliances, tile, and lighting are placed and inspected to the agreed design. A final city inspection issues the certificate of occupancy and the ADU is ready for use.
Who Is a Strong 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 available square footage under zoning rules, you're already a strong candidate. Homeowners wanting to add a revenue stream through rental are among the most common ADU construction clients, along with families navigating multigenerational living situations.
ADU construction also suits someone who needs a dedicated professional workspace and wants a private work environment that doesn't interfere with your family's daily life. Real estate-minded homeowners who are building a portfolio are also well suited for ADU construction, since rental income frequently offsets build costs.
Those who should discuss alternatives first include properties with significant setback limitations. Sites with underground infrastructure conflicts may need a modified approach. Brother & Brother Builders reviews each property individually and honestly to recommend the right path forward.
ADU Construction Frequently Asked Questions
How long does ADU construction usually take from start to finish?
The full timeline for ADU construction commonly spans six to fourteen months, based on the project scope and how quickly approvals come through. Permitting alone can take several months in San Jose, so starting early is important. Straightforward interior conversions can move faster, while larger new construction ADUs take longer to complete.
What does ADU construction cost in San Jose?
Budget requirements differ based on project complexity and finishes selected. In the San Jose area, ADU construction generally falls between $150,000 to $400,000 or more for a detached new build. Garage conversions often come in under, sometimes in the $80,000 to $150,000 range. A precise cost projection can only be produced following a thorough property review.
Is ADU construction intrusive while it's underway?
The day-to-day impact depends on the project's location on your property. Detached backyard builds are usually easier to live alongside, since work happens away from the main house. Projects that connect to the main structure may create short-term inconveniences 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?
Generally speaking, you do not need to vacate your house during ADU construction. The vast majority of projects are set read more up to let you remain on the property throughout the construction timeline. There are edge cases if significant structural connections require temporary shutoffs in ways that require short-term access disruption. 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?
Any ADU built to code with professional oversight can be expected to last as long as your primary home — typically 50 years or more. Durability depends to the systems installed, whether the unit is properly cared for, and whether systems like roofing and plumbing are serviced regularly. We select high-quality components and follow all code requirements to deliver a structure that stands the test of time.
ADU Construction for San Jose Homeowners
The communities throughout San Jose provide a variety of property types that are perfectly suited for ADU construction. Homeowners in the Willow Glen neighborhood have found their lots work well for both attached and detached projects. Neighborhoods near Blossom Hill Road are increasingly popular for ADU construction 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 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 this region's building landscape means more accurate timelines and budgets from design through the final walkthrough.
Book Your ADU Construction Assessment Today
When you want to add an ADU to your property, Brother & Brother Builders is the team to call. Our builders provide years of hands-on experience in ADU construction across a wide range of project types — from simple garage conversions to multi-room backyard residences. Every project starts with a detailed, no-pressure consultation where we understand your vision and share clear expectations of what the project will involve.
Reach out to our team to schedule a site visit. Even if you're just exploring the idea, we're glad to answer questions, share examples of our work and make sure you feel confident before committing. 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