Expand Your Home with Professional ADU Construction
Homeowners across San Jose, CA are discovering that adding an accessory dwelling unit is one of the smartest investments they can make. ADU construction opens the door to a flexible new living space on your existing property — whether you want to house a family member. Brother & Brother Builders has supported hundreds of local homeowners see these visions to life with skill and care.
The interest in ADU construction has increased significantly in recent years, and it's easy to understand why. California state law now makes it easier for homeowners to add these secondary units, and local municipalities like San Jose have supported the trend as a way to expand the housing supply. If you're planning a detached backyard cottage, a garage conversion, or an attached addition, ADU construction offers greater control over how your property works.
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 considerations, and the design choices that make an ADU truly livable. When you're ready to explore what ADU construction could look like on your property, this guide covers everything you need to know.
What Is an ADU Build?
ADU construction refers to the process of engineering, filing for, and completing an accessory dwelling unit on a residential property. An accessory dwelling unit is a fully independent living space — equipped with 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 setbacks, zoning, utility access, and structural feasibility. From there, blueprints are prepared and submitted to the city for permit approval. Once approvals are in place, ADU construction moves into the physical build phase — which includes foundation work, framing, roofing, plumbing, electrical, insulation. The result is a move-in-ready living unit attached to or separate from your main home.
What separates excellent ADU construction from an average project is the level of craftsmanship at every stage. Materials must be selected to match the primary home's aesthetic. Systems like wiring and water supply must be designed to handle full-time occupancy. Brother & Brother Builders treats each project with the same technical discipline we use on major custom home projects.
Key Advantages 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.
- Monthly Cash Flow — 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 provides adult children a comfortable home of their own without losing proximity to the family.
- Design Flexibility — From open-plan one-bedrooms, ADU construction is adaptable to your household's priorities.
- Faster Permitting in California — Recent state legislation has reduced the permitting obstacles associated with ADU construction, resulting in a timeline that is faster and less expensive than ever before.
- Efficient Use of Your Lot — Building an ADU maximizes the land you already own instead of expanding urban sprawl, which contributes to sustainability goals.
- Independent Living Areas — Unlike a bedroom addition, ADU construction delivers a genuinely independent unit where occupants have full privacy.
- Lasting Financial Benefit — A well-built ADU remains an asset 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 team visits your property to evaluate setbacks, lot coverage limits, and utility connections. This phase answers exactly what can be built before any resources go toward planning.
- Blueprint Development and Layout Design — Experienced draftspeople create detailed floor plans reflecting your priorities. Space is thoughtfully allocated to maximize function and livability.
- Permitting and City Approval — ADU construction in San Jose demands documentation to the city's building department for review and approval. Brother & Brother Builders coordinates the permitting on your behalf, responding to review feedback promptly.
- Site Preparation and Foundation Work — Once permits are approved, on-site work kicks off. This covers land preparation, laying the structural base, and running initial plumbing and electrical conduits.
- Shell Construction and Exterior Finishing — Framing is completed followed by weatherproofing and exterior finish materials. This phase, the ADU takes its visible shape.
- MEP Systems Rough-In — Skilled tradespeople install the water supply, drain lines, and electrical panel that make the ADU fully functional. Every system is reviewed at required milestones throughout ADU construction.
- Finishes, Fixtures, and Final Walkthrough — Flooring, cabinetry, fixtures, paint are fitted and completed to the approved plan. A last official inspection grants legal occupancy status and your new space is cleared for use.
Who Is a Good Candidate for ADU Construction?
Homeowners who benefit most from ADU construction typically fall into 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 motivated ADU construction clients, along with families supporting elderly parents.
You may also be someone who works from home and wants a separate office or studio space that is distinct from your family's daily life. Property investors and rental owners who are building a portfolio are also well suited for ADU construction, since rental income frequently offsets build costs.
Those who should discuss alternatives first include sites with unusual utility access challenges. Very small lots or properties with easements may require additional review. Brother & Brother Builders reviews each property case by case to advise you on what's feasible.
ADU Construction FAQ
How long does ADU construction typically take from start to finish?
The full timeline for ADU construction usually runs between six to fourteen months, depending on design complexity and how quickly approvals come through. Permitting alone can take two to four months in San Jose, so beginning the process sooner rather than later is wise. Simpler garage conversions often finish in the lower end of the range, while custom detached builds fall toward the upper end of the timeline.
What does ADU construction typically cost?
Costs vary widely based on project complexity and finishes selected. Locally, ADU construction generally falls between $150,000 to $400,000 or more for a fully custom construction. Attached ADU additions tend to cost less, sometimes in the $80,000 to $150,000 range. A precise cost projection can only be given after completing a thorough property review.
Is ADU construction intrusive while it's underway?
The level of disruption depends on whether you're converting existing space or building new. New construction in the rear yard are generally the least intrusive, 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 about what to expect at each stage.
Do I need to vacate the property during ADU construction?
Generally speaking, you are not required to vacate your primary residence during ADU construction. The vast majority of projects are set up to let you stay in your primary unit throughout the construction timeline. Exceptions may arise if major utility upgrades affect the main house in ways that briefly affect habitability. 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?
An ADU constructed with quality materials is designed to last as long as your primary home — indefinitely with proper upkeep. Longevity is tied to the quality of materials used, whether the unit is properly cared for, and how proactively issues are resolved over time. Our builds use high-quality components and build to current California residential standards to deliver a structure that stands the test of time.
ADU Construction for Local Homeowners
The communities throughout San Jose provide a wide range of property types that are well suited for ADU construction. Residents in the Rose Garden district often discover their properties work well for both attached and detached projects. Neighborhoods near Blossom Hill Road are seeing more homeowners add secondary units as housing demand rises. Whether your property is near downtown San Jose, our team has likely worked nearby.
Local regulatory bodies in this area follows defined procedures 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 this region's building landscape means fewer surprises from kickoff through certificate of occupancy.
Start Your ADU Construction Assessment Today
When you want to move forward with ADU construction, Brother & Brother Builders is ready to guide you. Our experts offer years of hands-on experience in ADU construction including all types of project types — from simple garage conversions to multi-room backyard residences. Every project starts with a comprehensive site assessment where we understand your vision and share clear expectations of what ADU construction on your property will look like.
Get in touch with our office to schedule a site visit. Whether you're in the early stages of planning, we enjoy answer questions, share examples of our work and help you take the next step. Building an ADU is a major decision — and our goal is to ensure it delivers real value.
Brother & adu construction Brother Builders | 3109 Stevens Creek Boulevard | San Jose CA 95117 | (888) 412-2632