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 create a private workspace. Brother & Brother Builders has guided hundreds of local homeowners bring these projects to life with precision and care.
The interest in ADU construction has surged in recent years, and it's easy to understand why. California state law now makes it easier for homeowners to construct 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 provides increased control over how your property functions.
At Brother & Brother Builders, we bring years of hands-on experience to every ADU construction job. Our team is familiar with city and county requirements, the engineering requirements, and the design choices that make an ADU beautiful. Should you want to learn about what ADU construction could mean for your property, this guide covers everything you need to know.
What Is the ADU Construction Process?
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 — including a kitchen, bathroom, sleeping area, and its own entryway — 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, everything kicks off with a thorough property evaluation, where our professionals evaluate property boundaries, available square footage, and infrastructure capacity. From there, architectural drawings are prepared and submitted to the local building department. Once the paperwork is cleared, ADU construction moves into the physical build phase — which encompasses site preparation, framing, roofing, plumbing, electrical, insulation. The result is a fully functional living unit adjacent to or detached from your main home.
The difference between a good and a great ADU build is the level of craftsmanship at every stage. Products need to be chosen to here match the primary home's aesthetic. Systems like HVAC and drainage must be designed to handle full-time occupancy. Brother & Brother Builders approaches every build 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 leaving the property.
- Personalized Layouts — From open-plan one-bedrooms, ADU construction is adaptable to the intended occupant's lifestyle.
- Faster Permitting in California — Recent state legislation has minimized the red tape associated with ADU construction, resulting in a timeline that is faster and less expensive than ever before.
- Responsible Property Development — Building an ADU works within your current footprint instead of expanding urban sprawl, which aligns with sustainability goals.
- Separate Entrances and Spaces — Unlike a bedroom addition, ADU construction produces a fully self-contained unit where occupants have full privacy.
- Durable Return on Investment — A well-built ADU remains an asset for decades, providing both functional space and financial upside.
The ADU Construction Process Step by Step
- Site Evaluation and Zoning Analysis — Our experts review your property to evaluate setbacks, lot coverage limits, and utility connections. This stage clarifies exactly what's possible before any time is invested in drawings.
- Architectural Drafting and Space Planning — Experienced draftspeople create detailed floor plans based on your goals. Space is thoughtfully allocated to maximize function and livability.
- Permit Submission and Municipal Review — 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, resolving any revision requests promptly.
- Ground Prep and Structural Base — Once permits are issued, on-site work kicks off. This involves leveling and prepping the ground, completing foundation work, and running initial plumbing and electrical conduits.
- Structural Framing and Weatherproofing — The structural frame is erected followed by roofing, siding, windows, and exterior doors. At this stage, the ADU transforms from a concept to a building.
- MEP Systems Rough-In — Licensed subcontractors install the water supply, drain lines, and electrical panel that make the ADU ready for occupancy. Every system is reviewed at designated stages throughout ADU construction.
- Finishes, Fixtures, and Final Walkthrough — Trim, appliances, tile, and lighting are installed and finished to your specifications. 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 generally fit within a few common profiles. If you are a homeowner with enough lot space to meet setback requirements, you're already in a good starting place. 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 works from home and wants a detached creative or business space that remains away from your family's daily life. Landlords and real estate investors who are building a portfolio are also a natural fit for ADU construction, since the return on investment is well-documented.
Those who should discuss alternatives first include sites with unusual utility access challenges. Parcels in historic districts or HOA-restricted communities may need a modified approach. Brother & Brother Builders reviews each property on its own merits to advise you on what's feasible.
ADU Construction Common Questions Answered
How long does ADU construction usually take from start to finish?
The full timeline for ADU construction typically ranges from six to fourteen months, based on the project scope and local permitting timelines. Permitting alone can take a significant portion of the overall timeline in San Jose, so planning ahead matters. Simpler garage conversions can move faster, while larger new construction ADUs take longer to complete.
What does ADU construction typically cost?
Budget requirements differ based on whether it's a conversion or new construction. In the San Jose area, ADU construction commonly costs $150,000 to $400,000 or more for a standalone backyard unit. Garage conversions often come in under, sometimes between $75,000 and $140,000. A detailed estimate can only be produced following a full site assessment.
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 usually easier to live alongside, 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. We provide advance notice about what to expect at each stage.
Do I need to leave my home during ADU construction?
In most cases, you are not required to vacate your house during ADU construction. Most job sites are designed so that you continue living in the home throughout the build. Certain situations could require a brief departure if major utility upgrades affect the main house in ways that temporarily impact livability. Our construction supervisors will discuss these scenarios during the planning phase.
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 — often several decades with routine maintenance. How long it lasts comes down to the standard of construction, how consistently minor repairs are addressed, and whether systems like roofing and plumbing are serviced regularly. We select residential-grade products rated for longevity and build to current California residential standards to deliver a structure that stands the test of time.
ADU Construction for San Jose Homeowners
The communities throughout San Jose provide a diverse mix of property types that are perfectly suited for ADU construction. Residents in the Rose Garden district often discover their properties work well for both attached and detached projects. The Berryessa area are increasingly popular for ADU construction as families expand. If you're located closer to Evergreen, our team has project experience in the area.
San Jose's permitting office applies particular standards for ADU construction that our team navigates routinely. Location near major arterials like Story Road or Tully Road can influence utility connection requirements for a given ADU project. Our familiarity with the San Jose permitting environment means smoother project delivery from the first meeting to the final inspection.
Start Your ADU Construction Planning Session Today
If you're ready to move forward with ADU construction, Brother & Brother Builders is the team to call. Our builders provide years of hands-on experience in ADU construction including all types of project types — from simple garage conversions to fully independent secondary homes. The process begins with a comprehensive site assessment where we learn what you're trying to accomplish and share clear expectations of what's achievable.
Reach out to our team to set up your consultation. No matter where you are in the decision-making process, we're glad to discuss timelines, costs, and design possibilities and help you take the next step. 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