Expand Your Home with Expert ADU Construction
Homeowners across San Jose, CA are realizing that adding an accessory dwelling unit is one of the most rewarding investments they can make. ADU construction provides a versatile new living space on your existing property — whether you want to house a family member. Brother & Brother Builders has supported hundreds of local homeowners turn these plans to life with craftsmanship and care.
The interest in ADU construction has surged in recent years, and it's easy to understand why. California state law has simplified the process for homeowners to add these secondary units, and local municipalities like San Jose have encouraged the trend as a way to address housing needs. If you're planning a detached backyard cottage, a garage conversion, or an attached addition, ADU construction gives you more control over how your property works.
At Brother & Brother Builders, we bring years of hands-on experience to every ADU construction project. Our team is familiar with city and county requirements, the engineering considerations, and the planning steps that make an ADU functional. When you're ready to explore what ADU construction could mean for your property, this guide explains 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 self-contained living space — featuring a kitchen, bathroom, sleeping area, and its own access point — that exists on the same lot 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 thorough property evaluation, where our team evaluate setbacks, zoning, utility access, and structural feasibility. From there, blueprints are prepared and submitted to the local building department. Once permits are secured, ADU construction moves into the physical build phase — which includes foundation work, framing, mechanical systems, weatherproofing, and interior finishing. 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 attention to detail at every stage. Products need to be chosen to complement the existing structure. Systems like HVAC and drainage must be designed to handle full-time occupancy. Brother & Brother Builders handles every ADU construction job with the same professional rigor we bring to full custom home projects.
Key Reasons to Choose ADU Construction
- Higher Resale Potential — ADU construction adds measurable market value to your property, often generating strong equity gains when it's time to sell.
- Revenue Generation — A completed ADU may be listed as a long-term rental or short-term vacation unit, generating steady monthly revenue for the homeowner.
- Multi-Generational Living — ADU construction offers family members a private, independent living space without losing proximity to the family.
- Customization Options — From two-bedroom configurations, ADU construction can be tailored to your specific needs.
- Faster Permitting in California — Recent state legislation has cut down the barriers and delays associated with ADU construction, making the process that is faster and less expensive than ever before.
- Responsible Property Development — Building an ADU works within your current footprint instead of expanding urban sprawl, which contributes to sustainability goals.
- Independent Living Areas — Unlike a bedroom addition, ADU construction creates a truly separate unit where tenants live autonomously.
- Durable Return on Investment — A well-built ADU holds its value for many years and generates both functional space and financial upside.
The ADU Construction Journey Step by Step
- Initial Property Assessment and Feasibility Review — Our experts review your property to determine what type of ADU is allowed and where it can be placed. This step tells you exactly what's possible before any time is invested in drawings.
- Custom Design and Architectural Planning — Our design team 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 requires submitting plans to the city's building department for review and approval. We manage this entire process on your behalf, resolving any revision requests promptly.
- Excavation and Foundation Installation — Once permits are approved, the build starts. This covers land preparation, completing foundation work, and running initial plumbing and electrical conduits.
- Structural Framing and Weatherproofing — The structural frame is erected followed by roofing, siding, windows, and exterior doors. At this stage, the ADU takes its visible shape.
- MEP Systems Rough-In — Licensed subcontractors install the plumbing lines, electrical wiring, and HVAC systems that make the ADU fully functional. Inspections are completed at required milestones throughout ADU construction.
- Interior Completion and City Sign-Off — Flooring, cabinetry, fixtures, paint are placed and inspected to the approved plan. A closing municipal review issues the certificate of occupancy and the ADU is ready for use.
Who Is a Good Candidate for ADU Construction?
Property owners who are best suited from ADU construction typically fall into a few clear categories. If you have a residential property with a backyard, garage, or basement that could be converted, you're already a strong candidate. Homeowners hoping to offset mortgage costs through rental are among the most financially driven 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 is distinct from your family's daily life. Real estate-minded homeowners who are building a portfolio are also well suited for ADU construction, since the long-term value is proven.
Situations where ADU construction may not be the best first step include sites with unusual utility access challenges. Very small lots or properties with easements may require additional review. Our team can assess each property on its own merits to provide realistic options.
ADU Construction Frequently Asked Questions
How long does ADU construction usually take from start to finish?
The full timeline for ADU construction typically ranges from six to fourteen months, based on the project scope and city review schedules. City review on its own can take two to four months in San Jose, so planning ahead matters. Simpler garage conversions often finish in the lower end of the range, while larger new construction ADUs fall toward the upper end of the timeline.
What does ADU construction typically cost?
Costs vary widely based on whether it's a conversion or new construction. 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 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?
How much the build affects daily life depends on the project's location on your property. New construction in the rear yard are usually easier to live alongside, since the crew operates at a distance from your living areas. Projects that connect to the main structure may involve some shared wall work during certain phases of construction. Brother & Brother Builders keeps you informed check here about any phases that may affect your routine.
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. There are edge cases if interior conversion work touches shared systems in ways that require short-term access disruption. Our project managers will discuss these scenarios during the planning phase.
How long will an ADU built through professional ADU construction last?
An ADU constructed with quality materials should last as long as any standard residential structure — often several decades with routine maintenance. Durability depends to the systems installed, whether the unit is properly cared for, and if mechanical components are maintained on schedule. Brother & Brother Builders specifies commercial-grade materials and follow all code requirements to protect your investment for the long haul.
ADU Construction for Local Homeowners
The communities throughout San Jose provide a variety of property types that are well suited for ADU construction. Homeowners in the Willow Glen neighborhood have found their lots are well configured for ADU builds. Communities around the Capitol Expressway corridor 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.
San Jose's permitting office applies particular standards for ADU construction that our team navigates routinely. Location near major arterials like Story Road or Tully Road can influence utility connection requirements for a given ADU project. Our team's knowledge of this region's building landscape means smoother project delivery from kickoff through certificate of occupancy.
Start Your ADU Construction Assessment Today
Should you be thinking about how to add an ADU to your property, Brother & Brother Builders is ready to guide you. Our experts offer proven skills in ADU construction across a wide range of project types — from simple garage conversions to large custom detached cottages. Our approach opens with a detailed, no-pressure consultation where we listen to your goals and share clear expectations of what the project will involve.
Get in touch with our office to schedule a site visit. No matter where you are in the decision-making process, we enjoy discuss timelines, costs, and design possibilities and make sure you feel confident before committing. Building an ADU is a major decision — and our goal is to ensure it delivers real value.
Brother & Brother Builders | 3109 Stevens Creek Boulevard | San Jose CA 95117 | (888) 412-2632