Expand Your Home with Professional ADU Construction
Families in San Jose, CA are discovering that adding an accessory dwelling unit is one of the most rewarding 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 supported hundreds of local homeowners bring these projects to life with precision and care.
The popularity of ADU construction has surged in recent years, and it's no mystery. California state law now makes it easier for homeowners to build these secondary units, and local municipalities like San Jose have encouraged 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 provides increased control over how your property works.
At Brother & here Brother Builders, we bring years of hands-on experience to every ADU construction build. Our team is familiar with city and county requirements, the engineering requirements, and the design choices 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 an ADU Build?
ADU construction describes the process of planning, approving, and constructing an accessory dwelling unit on a residential property. An accessory dwelling unit is a self-contained living space — including 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 basement or interior conversions.
Mechanically, everything kicks off with a comprehensive review of your lot, where our team evaluate property boundaries, available square footage, and infrastructure capacity. From there, blueprints are prepared and submitted to the city for permit approval. Once approvals are in place, ADU construction transitions to the physical build phase — which includes foundation work, framing, roofing, plumbing, electrical, insulation. The result is a completely finished living unit connected to or independent of your main home.
The difference between a good and a great ADU build is the level of craftsmanship at every stage. Components should be specified to complement the existing structure. Systems like plumbing and electrical must be built for long-term residential demand. Brother & Brother Builders treats each project with the same professional rigor we apply to large-scale custom home projects.
Key Reasons to Choose ADU Construction
- Higher Resale Potential — 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 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 offers family members a self-contained residence without leaving the property.
- Design Flexibility — From open-plan one-bedrooms, ADU construction may be customized to your household's priorities.
- Faster Permitting in California — Recent state legislation has cut down the permitting obstacles associated with ADU construction, resulting in a timeline that is faster and more cost-efficient than ever before.
- Efficient Use of Your Lot — Building an ADU maximizes the land you already own instead of requiring new development, which supports broader sustainability goals.
- Privacy for All Residents — Unlike a bedroom addition, ADU construction produces a fully self-contained unit where occupants have full privacy.
- Lasting Financial Benefit — A well-built ADU holds its value for the long haul by offering both usable housing and equity growth.
The ADU Construction Journey Step by Step
- Property Walkthrough and Feasibility Check — Our experts review your property to analyze zoning rules, slope conditions, and available square footage. This phase answers exactly what ADU types will work before any resources go toward planning.
- Blueprint Development and Layout Design — Our design team create detailed floor plans based on your goals. Layouts are carefully considered to maximize function and livability.
- Permitting and City Approval — ADU construction in San Jose requires submitting plans to the city's building department for inspection and clearance. Our team handles all submissions on your behalf, addressing any city comments promptly.
- Site Preparation and Foundation Work — Once permits are issued, on-site work kicks off. This includes grading the site, laying the structural base, and establishing utility connections.
- Shell Construction and Exterior Finishing — Framing is completed followed by weatherproofing and exterior finish materials. This phase, the ADU transforms from a concept to a building.
- Interior Systems and Infrastructure — 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 — Countertops, hardware, finishes, and fixtures are fitted and completed to your specifications. A closing municipal review 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 recognizable groups. If you have a residential property with a backyard, garage, or basement that could be converted, you're already well-positioned. 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.
Another strong candidate is someone who needs a dedicated professional workspace and wants a separate office or studio space that is distinct from your family's daily life. Landlords and real estate investors who are building a portfolio are also well suited for ADU construction, since the long-term value is proven.
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 on its own merits to recommend the right path forward.
ADU Construction Common Questions Answered
How long does ADU construction generally take from start to finish?
The total process for ADU construction usually runs between six to fourteen months, influenced by the type of unit being built and local permitting timelines. Permitting alone can take several months in San Jose, so starting early is important. Straightforward interior conversions can move faster, while custom detached builds take longer to complete.
What does ADU construction usually run in terms of budget?
Costs vary widely 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 detached new build. Attached ADU additions are generally priced lower, sometimes starting around $80,000 depending on scope. An accurate budget can only be given after completing a thorough property review.
Is ADU construction intrusive while it's underway?
The day-to-day impact depends on where the ADU is being built. New construction in the rear yard are generally the least intrusive, since the construction zone is separate. Garage conversions or attached additions may require temporary access during specific stages like framing or MEP rough-in. We provide advance notice about upcoming work and timelines.
Do I need to leave my home during ADU construction?
In most cases, you are not required to vacate your main home during ADU construction. The vast majority of projects are structured to allow you remain on the property throughout the construction timeline. Exceptions may arise if significant structural connections require temporary shutoffs in ways that require short-term access disruption. Our construction supervisors will flag these situations during the kickoff meeting.
How long will an ADU built through professional ADU construction remain in good condition?
A well-built ADU is designed to last as long as any standard residential structure — typically 50 years or more. How long it lasts comes down to the standard of construction, whether the unit is properly cared for, 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 deliver a structure that stands the test of time.
ADU Construction for Local Homeowners
The communities throughout San Jose provide a diverse mix of property types that are perfectly suited for ADU construction. Homeowners in the Willow Glen neighborhood have found their lots accommodate detached backyard units nicely. Communities around the Capitol Expressway corridor are seeing more homeowners add secondary units as families expand. From neighborhoods near the Guadalupe River Park corridor to those near Branham Lane, our team has likely worked nearby.
Local regulatory bodies in this area has developed specific protocols for ADU construction that require a builder familiar with local expectations. Access to infrastructure along thoroughfares like Monterey Road can affect how quickly permits are approved for a given ADU project. Our familiarity with these local conditions means smoother project delivery from kickoff through certificate of occupancy.
Start Your ADU Construction Assessment Today
Should you be thinking about how to explore what an ADU could look like on your lot, Brother & Brother Builders is the team to call. Our builders provide proven skills in ADU construction including all types of project types — from simple garage conversions to large custom detached cottages. Our approach opens with a thorough and honest property review where we listen to your goals and provide an honest assessment of what ADU construction on your property will look like.
Reach out to our team to begin the conversation. No matter where you are in the decision-making process, we enjoy walk through your options, review completed projects and make sure you feel confident before committing. 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