Expand Your Home with Expert ADU Construction
Property owners throughout San Jose, CA are finding 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 guided hundreds of local homeowners bring these projects to life with craftsmanship and care.
The interest in ADU construction has grown rapidly in recent years, and it's not hard to see why. California state law has streamlined permitting 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 more info to build a detached backyard cottage, a garage conversion, or an attached addition, ADU construction gives you more control over how your property serves your household.
At Brother & Brother Builders, we draw on extensive hands-on experience to every ADU construction project. Our team knows the San Jose building codes, the engineering details, and the aesthetic decisions that make an ADU truly livable. Should you want to learn about what ADU construction could mean for your property, this guide will walk you through 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 — featuring a kitchen, bathroom, sleeping area, and its own entrance — that exists on the same lot 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 work starts with a detailed site assessment, where our builders evaluate property boundaries, available square footage, and infrastructure capacity. From there, blueprints are prepared and submitted to the city for permit approval. Once the paperwork is cleared, ADU construction transitions to the physical build phase — which includes foundation work, framing, roofing, plumbing, electrical, insulation. The result is a fully functional living unit connected to or independent of your main home.
What sets quality ADU construction apart is the attention to detail at every stage. Materials must be selected to match the primary home's aesthetic. Systems like wiring and water supply must be built for long-term residential demand. Brother & Brother Builders approaches every build 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.
- 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.
- Space for Loved Ones — ADU construction provides adult children a comfortable home of their own without leaving the property.
- Customization Options — From modern studio layouts, ADU construction can be tailored 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.
- Efficient Use of Your Lot — Building an ADU maximizes the land you already own instead of expanding urban sprawl, which supports broader sustainability goals.
- Independent Living Areas — Unlike a bedroom addition, ADU construction produces a fully self-contained unit where residents have their own space.
- Long-Term Investment Security — A well-built ADU continues to produce returns for decades, providing both livable square footage and monetary benefit.
The ADU Construction Process Step by Step
- Property Walkthrough and Feasibility Check — 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.
- Architectural Drafting and Space Planning — Experienced draftspeople create precise architectural drawings tailored to your needs. Every square foot is planned 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, responding to review feedback promptly.
- Site Preparation and Foundation Work — Once permits are issued, on-site work kicks off. This includes grading the site, completing foundation work, and establishing utility connections.
- Shell Construction and Exterior Finishing — Walls and roof systems go up followed by insulation, sheathing, and exterior cladding. During this step, the ADU becomes recognizable as a structure.
- Mechanical, Electrical, and Plumbing Installation — Skilled tradespeople install the heating, cooling, drainage, and power infrastructure that make the ADU fully functional. All work is inspected at designated stages throughout ADU construction.
- Interior Finishing and Final Inspections — Countertops, hardware, finishes, and fixtures are placed and inspected to the agreed design. A final city inspection grants legal occupancy status and the unit is officially approved for use.
Who Is a Right Fit for ADU Construction?
Homeowners who benefit most from ADU construction often belong to a few recognizable groups. If you own a single-family home with enough lot space to meet setback requirements, you're already a strong candidate. Homeowners looking to generate income 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 needs a dedicated professional workspace and wants a private work environment that remains away from your family's daily life. Real estate-minded homeowners who are building a portfolio are also well suited for ADU construction, since the return on investment is well-documented.
Those who should discuss alternatives first include lots that are below minimum size thresholds. Very small lots or properties with easements may face additional constraints. Our experts will evaluate each property on its own merits to recommend the right path forward.
ADU Construction Common Questions Answered
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 how quickly approvals come through. 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. Smaller detached units can move faster, while multi-room detached cottages require more time.
What does ADU construction cost in San Jose?
Budget requirements differ based on whether it's a conversion or new construction. In the San Jose area, ADU construction typically ranges from $150,000 to $400,000 or more for a fully custom construction. Garage conversions are generally priced lower, sometimes in the $80,000 to $150,000 range. A detailed estimate can only be produced following a thorough property review.
Is ADU construction disruptive while it's underway?
The level of disruption depends on the project's location on your property. New construction in the rear yard are typically less disruptive, since work happens away from the main house. Projects that connect to the main structure may require temporary access during specific stages like framing or MEP rough-in. Our team communicates clearly about any phases that may affect your routine.
Do I need to leave my home during ADU construction?
For the majority of homeowners, you do not need to vacate your primary residence during ADU construction. Most builds are designed so that 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 walk you through any potential disruptions during the kickoff meeting.
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 any standard residential structure — indefinitely with proper upkeep. Longevity is tied to the quality of materials used, whether the unit is properly cared for, and whether systems like roofing and plumbing are serviced regularly. We select high-quality components and build to current California residential standards to ensure lasting performance.
ADU Construction for Local Homeowners
San Jose's neighborhoods offer a diverse mix of property types that are perfectly suited for ADU construction. Property owners near the Almaden Valley area often discover their properties are well configured for ADU builds. The Berryessa area 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 applies particular standards for ADU construction that require a builder familiar with local expectations. Proximity to transit corridors can affect how quickly permits are approved for a given ADU project. Brother & Brother Builders' experience across these local conditions means more accurate timelines and budgets from the first meeting to the final inspection.
Book Your ADU Construction Planning Session Today
Should you be thinking about how to explore what an ADU could look like on your lot, Brother & Brother Builders is ready to guide you. Our experts offer proven skills in ADU construction across a wide range of project types — from small attached additions 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's achievable.
Reach out to our team to schedule a site visit. Even if you're just exploring the idea, our team is happy to 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