Unlock New Space with Expert ADU Construction
Homeowners across San Jose, CA are realizing that adding an accessory dwelling unit is one of the most practical investments they can make. ADU construction opens the door to a versatile new living space on your existing property — whether you want to create a private workspace. Brother & Brother Builders has helped hundreds of local homeowners turn these plans to life with craftsmanship and transparency.
The popularity of ADU construction has surged 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're building 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 draw on extensive hands-on experience to every ADU construction build. Our team is familiar with city and county requirements, the engineering considerations, and the planning steps that make an ADU functional. Should you want to learn about what ADU construction could do for your property, this guide explains everything you need to know.
What Is ADU Construction?
ADU construction refers to the process of planning, approving, and constructing 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 entryway — that sits on the same property as a primary residence. ADU construction includes various structural types, including detached backyard units, attached additions, garage conversions, and even below-grade dwelling units.
Mechanically, the process begins with a detailed site assessment, where our professionals evaluate property boundaries, available square footage, and infrastructure capacity. From there, design plans are prepared and submitted to the city for permit approval. Once approvals are in place, ADU construction moves into the physical build phase — which encompasses site preparation, framing, HVAC, drywall, flooring, and exterior finishes. The result is a move-in-ready living unit attached to or separate from your main home.
The difference between a good and a great ADU build is the level of craftsmanship at every stage. Materials must be selected to align with the neighborhood's character. Systems like wiring and water supply must be sized for independent daily use. Brother & Brother Builders handles every ADU construction job with the same technical discipline we bring to full custom home projects.
Key Benefits ADU Construction
- Boosted Home Equity — 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 can be rented as a long-term rental or short-term vacation unit, providing a consistent income stream for the homeowner.
- Multi-Generational Living — ADU construction provides adult children a comfortable home of their own without leaving the property.
- Design Flexibility — From two-bedroom configurations, ADU construction can be tailored to the intended occupant's lifestyle.
- Streamlined Approval Process — 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.
- Responsible Property Development — Building an ADU uses your existing lot instead of requiring new development, which supports broader sustainability goals.
- Independent Living Areas — Unlike a bedroom addition, ADU construction delivers a genuinely independent unit where tenants live autonomously.
- Lasting Financial Benefit — A well-built ADU continues to produce returns for many years and generates both livable square footage and monetary benefit.
The ADU Construction Procedure 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 phase answers exactly what's possible before any time is invested in drawings.
- Custom Design and Architectural 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 involves filing drawings 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, laying the structural base, and establishing utility connections.
- Structural Framing and Weatherproofing — The structural frame is erected followed by roofing, siding, windows, and exterior doors. At this stage, the ADU becomes recognizable as a structure.
- MEP Systems Rough-In — Skilled tradespeople install the water supply, drain lines, and electrical panel that make the ADU ready for occupancy. All work is inspected at each code checkpoint throughout ADU construction.
- Interior Completion and City Sign-Off — Flooring, cabinetry, fixtures, paint are placed and inspected to your specifications. A final city inspection issues the certificate of occupancy and your new space is cleared for use.
Who Is a Good Candidate for ADU Construction?
Homeowners who benefit most from ADU construction often belong to a few common profiles. If you own a single-family home with a backyard, garage, or basement that could be converted, you're already well-positioned. Homeowners hoping to offset mortgage costs through rental are among the most financially driven ADU construction clients, along with families supporting elderly parents.
ADU construction also suits someone who works from home and wants a separate office or studio space that is distinct from your family's daily life. Landlords and real estate investors who want to maximize their land 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 sites with unusual utility access challenges. Very small lots or properties with easements may face additional constraints. Our team can assess each property individually and honestly to recommend the right path forward.
ADU Construction FAQ
How long does ADU construction generally take from start to finish?
The total process for ADU construction usually runs between six to fourteen months, based on the project scope and local permitting timelines. 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 require more time.
What does ADU construction cost in San Jose?
Costs vary widely based on the type and size of the ADU. Locally, ADU construction generally falls between $150,000 to $400,000 or more for a detached new build. Interior conversion projects are generally priced lower, sometimes in the $80,000 to $150,000 range. An accurate budget can only be produced following a full site assessment.
Is ADU construction intrusive while it's underway?
The day-to-day impact depends on the project's location on your property. Standalone ADU projects are typically less disruptive, since the crew operates at a distance from your living areas. Projects that connect to the main structure may create short-term inconveniences during specific stages like framing or MEP rough-in. Brother & Brother Builders keeps you informed about any phases that may affect your routine.
Do I need to vacate the property during ADU construction?
Generally speaking, you are not required to vacate your primary residence during ADU construction. Most job sites are designed so that you remain on the property throughout the build. There are edge cases if interior conversion work touches shared systems in ways that briefly affect habitability. Our project managers will discuss these scenarios during the kickoff meeting.
How long will an ADU built through professional ADU construction remain in good condition?
An ADU constructed with quality materials should last as long as your primary home — often several decades with routine maintenance. How long it lasts comes down to the standard of construction, whether the unit is properly cared for, and if mechanical components are maintained on schedule. Our builds use high-quality components and comply with all local building codes to protect your investment for the long haul.
ADU Construction for San Jose Homeowners
Residential areas across San Jose present a variety of property types that are perfectly suited for ADU construction. Residents in the Rose Garden district often discover their properties accommodate detached backyard units nicely. The Berryessa area are seeing more homeowners add secondary units as multigenerational living becomes more common. Whether your property is near downtown San Jose, our team has project experience in the area.
The City of San Jose's building department applies particular standards for ADU construction that our team navigates routinely. Access to infrastructure along thoroughfares like Monterey Road can affect how quickly permits are approved for a given ADU project. Our familiarity with this region's building landscape means smoother project delivery from kickoff through certificate of occupancy.
Schedule Your ADU Construction Assessment Today
If you're ready to move forward with ADU construction, Brother & Brother Builders is here to help. We bring years of hands-on experience in ADU construction for many different project types — from small more info attached additions to multi-room backyard residences. Our approach opens with a detailed, no-pressure consultation where we listen to your goals and share clear expectations of what ADU construction on your property will look like.
Get in touch with our office to set up your consultation. Whether you're in the early stages of planning, our team is happy to answer questions, share examples of our work and make sure you feel confident before committing. Building an ADU is a major decision — and we're committed to helping you get it right.
Brother & Brother Builders | 3109 Stevens Creek Boulevard | San Jose CA 95117 | (888) 412-2632