Expand Your Home with Expert ADU Construction
Property owners throughout San Jose, CA are realizing that adding an accessory dwelling unit is one of the most practical investments they can make. ADU construction provides a flexible new living space on your existing property — whether you want to generate rental income. Brother & Brother Builders has helped hundreds of local homeowners see these visions to life with precision and transparency.
The demand for ADU construction has grown rapidly 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 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 gives you more control over how your property works.
At Brother & Brother Builders, we bring years of hands-on experience to every ADU construction build. Our here team understands the local permitting process, the engineering considerations, and the planning steps that make an ADU truly livable. When you're ready to explore what ADU construction could mean for your property, this guide will walk you through everything you need to know.
What Is the ADU Construction Process?
ADU construction involves the process of engineering, filing for, and completing 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 access point — 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, the process begins with a detailed site assessment, where our builders evaluate lot dimensions, existing structures, soil conditions, and local code requirements. From there, architectural drawings are prepared and submitted to the local building department. Once permits are secured, ADU construction enters the physical build phase — which encompasses site preparation, framing, HVAC, drywall, flooring, and exterior finishes. The result is a completely finished living unit attached to or separate 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 align with the neighborhood's character. Systems like wiring and water supply must be built for long-term residential demand. Brother & Brother Builders handles every ADU construction job with the same professional rigor we apply to large-scale custom home projects.
Key Advantages ADU Construction
- Higher Resale Potential — ADU construction adds measurable market value to your property, often increasing appraised value substantially when it's time to sell.
- Monthly Cash Flow — A completed ADU may be listed as a long-term rental or short-term vacation unit, generating steady monthly revenue for the homeowner.
- Housing for Extended Family — ADU construction offers family members a comfortable home of their own without leaving the property.
- Design Flexibility — From open-plan one-bedrooms, ADU construction is adaptable to the intended occupant's lifestyle.
- Simplified Regulatory Path — Recent state legislation has minimized the red tape associated with ADU construction, resulting in a timeline that is faster and more cost-efficient than ever before.
- Responsible Property Development — Building an ADU uses your existing lot instead of consuming open land, which contributes to sustainability goals.
- Separate Entrances and Spaces — Unlike a bedroom addition, ADU construction creates a truly separate unit where occupants have full privacy.
- Lasting Financial Benefit — A well-built ADU continues to produce returns for many years and generates both usable housing and equity growth.
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 stage clarifies exactly what's possible before any time is invested in drawings.
- Blueprint Development and Layout Design — Experienced draftspeople create detailed floor plans reflecting your priorities. Every square foot is planned to create practical, comfortable living.
- 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.
- Ground Prep and Structural Base — Once permits are approved, physical construction begins. This includes grading the site, pouring the concrete foundation, and running initial plumbing and electrical conduits.
- Structural Framing and Weatherproofing — Walls and roof systems go up followed by insulation, sheathing, and exterior cladding. This phase, the ADU transforms from a concept to a building.
- Interior Systems and Infrastructure — Licensed subcontractors install the plumbing lines, electrical wiring, and HVAC systems that make the ADU operationally complete. All work is inspected at designated stages throughout ADU construction.
- Interior Finishing and Final Inspections — Flooring, cabinetry, fixtures, paint are placed and inspected to the agreed design. A closing municipal review confirms the unit is code-compliant and the unit is officially approved for use.
Who Is a Right Fit for ADU Construction?
Property owners who are best suited from ADU construction typically fall into a few common profiles. If you own a single-family home with a backyard, garage, or basement that could be converted, you're already a strong candidate. Homeowners wanting to add a revenue stream through rental are among the most financially driven ADU construction clients, along with families accommodating adult children who need housing.
Another strong candidate is someone who runs a small business and wants a private work environment that doesn't interfere with your family's daily life. Landlords and real estate investors who want to maximize their land are also well suited for ADU construction, since rental income frequently offsets build costs.
Situations where ADU construction may not be the best first step include sites with unusual utility access challenges. Parcels in historic districts or HOA-restricted communities may require additional review. Our team can assess each property individually and honestly to advise you on what's feasible.
ADU Construction FAQ
How long does ADU construction usually take from start to finish?
The total process for ADU construction typically ranges from six to fourteen months, influenced by the type of unit being built and city review schedules. The approval phase alone can take a significant portion of the overall timeline in San Jose, so beginning the process sooner rather than later is wise. Straightforward interior conversions may complete more quickly, while multi-room detached cottages take longer to complete.
What does ADU construction typically cost?
Costs vary widely based on the type and size of the ADU. In the San Jose area, ADU construction typically ranges from $150,000 to $400,000 or more for a fully custom construction. Attached ADU additions tend to cost less, sometimes starting around $80,000 depending on scope. A precise cost projection can only be given after completing 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. New construction in the rear yard are typically less disruptive, since the construction zone is separate. Garage conversions or attached additions may involve some shared wall work during key milestones. Our team communicates clearly about any phases that may affect your routine.
Do I need to vacate the property during ADU construction?
In most cases, you are not required to vacate your primary residence during ADU construction. The vast majority of projects are set up to let 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 discuss these scenarios during the kickoff meeting.
How long will an ADU built through professional ADU construction last?
A well-built ADU can be expected to last as long as any standard residential structure — indefinitely with proper upkeep. Longevity is tied to the quality of materials used, how well routine maintenance is performed, and how proactively issues are resolved over time. Our builds use high-quality components and comply with all local building codes to ensure lasting performance.
ADU Construction for San Jose Homeowners
Residential areas across San Jose present a variety of property types that are well suited for ADU construction. Property owners near the Almaden Valley area frequently see their parcels are well configured for ADU builds. Communities around the Capitol Expressway corridor are increasingly popular for ADU construction as families expand. If you're located closer to Evergreen, our team has project experience in the area.
The City of San Jose's building department applies particular standards for ADU construction that require a builder familiar with local expectations. Access to infrastructure along thoroughfares like Monterey Road can impact the design approach for a given ADU project. Our familiarity with these local conditions means more accurate timelines and budgets from design through the final walkthrough.
Schedule Your ADU Construction Assessment Today
When you want to explore what an ADU could look like on your lot, Brother & Brother Builders is the team to call. Our experts offer proven skills in ADU construction including all types of project types — from small attached additions to multi-room backyard residences. The process begins with a comprehensive site assessment where we learn what you're trying to accomplish and give you a realistic picture of what ADU construction on your property will look like.
Contact Brother & Brother Builders to begin the conversation. Whether you're in the early stages of planning, we enjoy answer questions, share examples of our work and give you the clarity you need to move forward. 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