Unlock New Space with Expert ADU Construction
Homeowners across San Jose, CA are finding 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 generate rental income. Brother & Brother Builders has guided hundreds of local homeowners turn these plans to life with craftsmanship and integrity.
The interest in ADU construction has increased significantly in recent years, and it's no mystery. California state law has simplified the process for homeowners to build these secondary units, and local municipalities like San Jose have encouraged the trend as a way to expand the housing supply. Whether you're building a detached backyard cottage, a garage conversion, or an attached addition, ADU construction offers greater control over how your property serves your household.
At Brother & Brother Builders, we draw on extensive hands-on experience to every ADU construction job. Our team understands the local permitting process, the engineering requirements, and the design choices that make an ADU beautiful. Should you want to learn 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 is located on the same parcel 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 detailed site assessment, where our builders evaluate property boundaries, available square footage, and infrastructure capacity. From there, architectural drawings are prepared and submitted to the relevant municipal authority. Once the paperwork is cleared, ADU construction transitions to the physical build phase — which includes foundation work, framing, HVAC, drywall, flooring, and exterior finishes. The result is a fully functional living unit attached to or separate from your main home.
What separates excellent ADU construction from an average project is the attention to detail at every stage. Materials must be selected to align with the neighborhood's character. Systems like plumbing and electrical must be sized for independent daily use. Brother & Brother Builders treats each project with the same high standards we apply to large-scale custom home projects.
Key Reasons to Choose ADU Construction
- Higher Resale Potential — ADU construction adds measurable market value to your property, often returning more than the build cost when it's time to sell.
- Rental Income Potential — A completed ADU is leasable as a long-term rental or short-term vacation unit, creating ongoing passive income for the homeowner.
- Space for Loved Ones — ADU construction gives aging parents a comfortable home of their own without moving to another neighborhood.
- Personalized Layouts — From two-bedroom configurations, ADU construction is adaptable to the intended occupant's lifestyle.
- Faster Permitting in California — Recent state legislation has reduced 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 requiring new development, 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 remains an asset for many years and generates both livable square footage and monetary benefit.
The ADU Construction Process Step by Step
- Property Walkthrough and Feasibility Check — Our experts review your property to analyze zoning rules, slope conditions, and available square footage. This stage clarifies exactly what ADU types will work before any resources go toward planning.
- Blueprint Development and Layout Design — Licensed architects and designers create precise architectural drawings tailored to your needs. Layouts are carefully considered to optimize daily use.
- Permitting and City Approval — ADU construction in San Jose requires submitting plans to the city's building department for review and approval. Brother & Brother Builders coordinates the permitting on your behalf, responding to review feedback promptly.
- Excavation and Foundation Installation — Once permits are issued, the build starts. This covers land preparation, pouring the concrete foundation, and running initial plumbing and electrical conduits.
- Framing, Roofing, and Exterior Work — Framing is completed followed by insulation, sheathing, and exterior cladding. This phase, the ADU transforms from a concept to a building.
- Mechanical, Electrical, and Plumbing Installation — Skilled tradespeople install the plumbing lines, electrical wiring, and HVAC systems that make the ADU operationally complete. All work is inspected at required milestones throughout ADU construction.
- Finishes, Fixtures, and Final Walkthrough — Flooring, cabinetry, fixtures, paint are installed and finished to the agreed design. A last official inspection grants legal occupancy status 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 typically fall into a few clear categories. If you own a single-family home with enough lot space to meet setback requirements, you're already a strong candidate. 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.
You may also be someone who needs a dedicated professional workspace and wants a private work environment that is distinct from your family's daily life. Landlords and real estate investors who already own residential properties are also a natural fit for ADU construction, since the long-term value is proven.
Situations where ADU construction may not be the best first step include lots that are below minimum size thresholds. Parcels in historic districts or HOA-restricted communities may need a modified approach. Our team can assess each property case by case to provide realistic options.
ADU Construction FAQ
How long does ADU construction generally take from start to finish?
The total process for ADU construction typically ranges from six to fourteen months, based on the project scope and local permitting timelines. Permitting alone can take two to four months in San Jose, so starting early is important. Smaller detached units often finish in the read more lower end of the range, while custom detached builds require more time.
What does ADU construction cost in San Jose?
Pricing depends on many factors based on whether it's a conversion or new construction. Locally, ADU construction generally falls between $150,000 to $400,000 or more for a standalone backyard unit. Attached ADU additions tend to cost less, sometimes starting around $80,000 depending on scope. A precise cost projection can only be produced following a formal feasibility evaluation.
Is ADU construction disruptive while it's underway?
The level of disruption depends on whether you're converting existing space or building new. Standalone ADU projects are generally the least intrusive, since the construction zone is separate. Projects that connect to the main structure may involve some shared wall work during key milestones. We provide advance notice about what to expect at each stage.
Do I need to leave my home during ADU construction?
For the majority of homeowners, you do not need to vacate your house during ADU construction. The vast majority of projects are structured to allow you remain on the property throughout the build. There are edge cases if interior conversion work touches shared systems in ways that temporarily impact livability. Our project managers will walk you through any potential disruptions during the planning phase.
How long will an ADU built through professional ADU construction hold up?
Any ADU built to code with professional oversight should last as long as the main residence — indefinitely with proper upkeep. How long it lasts comes down to the standard of construction, how consistently minor repairs are addressed, and if mechanical components are maintained on schedule. We select high-quality components and comply with all local building codes to ensure lasting performance.
ADU Construction for Local Homeowners
The communities throughout San Jose provide a variety of property types that are ideally positioned for ADU construction. Residents in the Rose Garden district often discover their properties are well configured for ADU builds. Communities around the Capitol Expressway corridor have seen growing ADU activity as families expand. Whether your property is near downtown San Jose, our team has project experience in the area.
Local regulatory bodies in this area applies particular standards for ADU construction that our team navigates routinely. Access to infrastructure along thoroughfares like Monterey Road can impact the design approach for a given ADU project. Brother & Brother Builders' experience across these local conditions means fewer surprises from kickoff through certificate of occupancy.
Book Your ADU Construction Planning Session Today
Should you be thinking about how 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 for many different project types — from small attached additions to large custom detached cottages. Our approach opens with a thorough and honest property review where we understand your vision and share clear expectations of what's achievable.
Reach out to our team to schedule a site visit. No matter where you are in the decision-making process, we enjoy answer questions, share examples of our work and make sure you feel confident before committing. This type of project is a meaningful commitment — and our goal is to ensure it delivers real value.
Brother & Brother Builders | 3109 Stevens Creek Boulevard | San Jose CA 95117 | (888) 412-2632