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 smartest investments they can make. ADU construction creates a flexible new living space on your existing property — whether you want to create a private workspace. Brother & Brother Builders has guided hundreds of local homeowners see these visions 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 simplified the process for homeowners to add these secondary units, and local municipalities like San Jose have embraced 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 functions.
At Brother & Brother Builders, we apply deep hands-on experience to every ADU construction job. Our team knows the San Jose building codes, the engineering requirements, and the design choices that make an ADU truly livable. If you've been thinking about what ADU construction could do for your property, this guide explains everything you need to know.
What Is ADU Construction?
ADU construction involves the process of engineering, filing for, and completing an accessory dwelling unit on a residential property. An accessory dwelling unit is a self-contained living space — equipped with a kitchen, bathroom, sleeping area, and its own access point — that sits on the same property 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, everything kicks off 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 local building department. Once approvals are in place, ADU construction enters the physical build phase — which includes foundation work, 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. Components should be specified to complement the existing structure. Systems like plumbing and electrical must be designed to handle full-time occupancy. Brother & Brother Builders handles every ADU construction job with the same professional rigor we bring to full custom home read more projects.
Key Benefits ADU Construction
- Higher Resale Potential — ADU construction delivers real market value to your property, often increasing appraised value substantially when it's time to sell.
- Rental Income Potential — A completed ADU is leasable as a long-term rental or short-term vacation unit, providing a consistent income stream for the homeowner.
- Multi-Generational Living — ADU construction offers family members a comfortable home of their own without losing proximity to the family.
- Customization Options — From open-plan one-bedrooms, ADU construction is adaptable to the intended occupant's lifestyle.
- Streamlined Approval Process — Recent state legislation has cut down the barriers and delays 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 uses your existing lot instead of expanding urban sprawl, which contributes to sustainability goals.
- Privacy for All Residents — Unlike a bedroom addition, ADU construction creates a truly separate unit where tenants live autonomously.
- Long-Term Investment Security — A well-built ADU continues to produce returns for the long haul by offering both livable square footage and monetary benefit.
The ADU Construction Process Step by Step
- Site Evaluation and Zoning Analysis — Our team visits your property to analyze zoning rules, slope conditions, and available square footage. This stage clarifies exactly what can be built before any resources go toward planning.
- Blueprint Development and Layout Design — Experienced draftspeople create precise architectural drawings tailored to your needs. Every square foot is planned to optimize daily use.
- 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 setting up utilities.
- Structural Framing and Weatherproofing — The structural frame is erected followed by roofing, siding, windows, and exterior doors. This phase, the ADU takes its visible shape.
- MEP Systems Rough-In — Certified technicians install the plumbing lines, electrical wiring, and HVAC systems that make the ADU fully functional. Inspections are completed at required milestones throughout ADU construction.
- Interior Finishing and Final Inspections — Countertops, hardware, finishes, and fixtures are placed and inspected to your specifications. A last official inspection issues the certificate of occupancy and your new space is cleared for use.
Who Is a Strong Candidate for ADU Construction?
Homeowners who benefit most from ADU construction typically fall into a few common profiles. If you have a residential property with a backyard, garage, or basement that could be converted, you're already a strong candidate. 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 already own residential properties are also a natural fit for ADU construction, since rental income frequently offsets build costs.
Those who should discuss alternatives first include properties with significant setback limitations. Parcels in historic districts or HOA-restricted communities may require additional review. Our experts will evaluate each property individually and honestly to advise you on what's feasible.
ADU Construction Frequently Asked Questions
How long does ADU construction generally take from start to finish?
The full timeline for ADU construction commonly spans six to fourteen months, based on the project scope and city review schedules. The approval phase alone can take two to four months in San Jose, so planning ahead matters. Simpler garage conversions often finish in the lower end of the range, while custom detached builds take longer to complete.
What does ADU construction typically cost?
Costs vary widely based on project complexity and finishes selected. In the San Jose area, ADU construction generally falls between $150,000 to $400,000 or more for a fully custom construction. Garage conversions often come in under, sometimes between $75,000 and $140,000. An accurate budget can only be developed after a full site assessment.
Is ADU construction disruptive while it's underway?
The day-to-day impact depends on the project's location on your property. New construction in the rear yard are usually easier to live alongside, since the construction zone is separate. Interior conversions may create short-term inconveniences during certain phases of construction. Our team communicates clearly about what to expect at each stage.
Do I need to leave my home during ADU construction?
In most cases, you won't have to vacate your house during ADU construction. Most builds are set up to let you continue living in the home throughout the build. Certain situations could require a brief departure if significant structural connections require temporary shutoffs in ways that require short-term access disruption. The team at Brother & Brother Builders will discuss these scenarios during the pre-construction consultation.
How long will an ADU built through professional ADU construction hold up?
An ADU constructed with quality materials can be expected to last as long as the main residence — indefinitely with proper upkeep. Longevity is tied to the systems installed, how well routine maintenance is performed, and how proactively issues are resolved over time. We select commercial-grade materials and follow all code requirements to ensure lasting performance.
ADU Construction for San Jose Homeowners
The communities throughout San Jose provide a diverse mix of property types that are ideally positioned for ADU construction. Homeowners in the Willow Glen neighborhood often discover their properties work well for both attached and detached projects. Communities around the Capitol Expressway corridor are seeing more homeowners add secondary units as housing demand rises. From neighborhoods near the Guadalupe River Park corridor to those near Branham Lane, our team has likely worked nearby.
San Jose's permitting office applies particular standards for ADU construction that require a builder familiar with local expectations. Proximity to transit corridors can influence utility connection requirements for a given ADU project. Our team's knowledge of these local conditions means smoother project delivery from the first meeting to the final inspection.
Book Your ADU Construction Planning Session Today
When you want to move forward with ADU construction, Brother & Brother Builders is here to help. Our experts offer licensed expertise in ADU construction across a wide range of project types — from simple garage conversions to large custom detached cottages. Every project starts with a comprehensive site assessment where we learn what you're trying to accomplish and provide an honest assessment of what ADU construction on your property will look like.
Reach out to our team to begin the conversation. Whether you're in the early stages of planning, we're glad to walk through your options, review completed projects and help you take the next step. ADU construction is a significant investment — and we're committed to helping you get it right.
Brother & Brother Builders | 3109 Stevens Creek Boulevard | San Jose CA 95117 | (888) 412-2632