Unlock New Space with Expert ADU Construction
Property owners throughout San Jose, CA are discovering that adding an accessory dwelling unit is one of the most rewarding investments they can make. ADU construction creates a flexible new living space on your existing property — whether you want to generate rental income. Brother & Brother Builders has helped hundreds of local homeowners bring these projects to life with skill and integrity.
The interest in ADU construction has grown rapidly in recent years, and it's not hard to see 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. Whether you're building a detached backyard cottage, a garage conversion, or an attached addition, ADU construction provides increased control over how your property serves your household.
At Brother & Brother Builders, we draw on extensive hands-on experience to every ADU construction project. Our team understands the local permitting process, the engineering requirements, and the planning steps that make an ADU truly livable. If you've been thinking about what ADU construction could look like on your property, this guide will walk you through everything you need to know.
What Is an ADU Build?
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 complete 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 includes various structural types, including detached backyard units, attached additions, garage conversions, and even interior space reconfigurations.
Mechanically, everything kicks off with a comprehensive review of your lot, where our team evaluate property boundaries, available square footage, and infrastructure capacity. From there, design plans are prepared and submitted to the relevant municipal authority. Once permits are secured, ADU construction enters 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. Products need to be chosen to 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 technical discipline we bring to full custom home projects.
Key Benefits ADU Construction
- Increased Property Value — ADU construction contributes significant market value to your property, often returning more than the build cost 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 moving to another neighborhood.
- Customization Options — From modern studio layouts, ADU construction may be customized to your household's priorities.
- Simplified Regulatory Path — Recent state legislation has minimized 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 aligns with sustainability goals.
- Independent Living Areas — Unlike a bedroom addition, ADU construction delivers a genuinely independent unit where occupants have full privacy.
- 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 determine what type of ADU is allowed and where it can be placed. This phase answers exactly what's possible before any resources go toward planning.
- Architectural Drafting and Space Planning — Experienced draftspeople create precise architectural drawings based on your goals. Space is thoughtfully allocated to maximize function and livability.
- Filing for Building Permits — ADU construction in San Jose involves filing drawings to the city's building department for sign-off and verification. Our team handles all submissions on your behalf, addressing any city comments promptly.
- Ground Prep and Structural Base — Once permits are issued, physical construction begins. This includes grading the site, laying the structural base, and running initial plumbing and electrical conduits.
- Structural Framing and Weatherproofing — The structural frame is erected followed by insulation, sheathing, and exterior cladding. This phase, the ADU takes its visible shape.
- MEP Systems Rough-In — Certified technicians install the water supply, drain lines, and electrical panel that make the ADU ready for occupancy. All work is inspected at required milestones throughout ADU construction.
- Interior Finishing and Final Inspections — Flooring, cabinetry, fixtures, paint are fitted and completed to the approved plan. A final city inspection confirms the unit is code-compliant 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 clear categories. If you have a residential property 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 accommodating adult children who need housing.
ADU construction also suits someone who works from home and wants a private work environment that doesn't interfere with your family's daily life. Real estate-minded homeowners who want to maximize their land are also well suited for ADU construction, since rental income frequently offsets build costs.
Homeowners who may want to pause and evaluate 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 provide realistic options.
ADU Construction FAQ
How long does ADU construction usually take from start to finish?
The total process for ADU construction commonly spans six to fourteen months, based on the project scope and how quickly approvals come through. City review on its own 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 can move faster, while larger new construction ADUs take longer to complete.
What does ADU construction typically cost?
Costs vary widely based on the type and size of the ADU. In the San Jose area, ADU construction generally falls between $150,000 to $400,000 or more for a standalone backyard unit. Garage conversions are generally priced lower, sometimes between $75,000 and $140,000. A detailed estimate can only be developed after a thorough property review.
Is ADU construction disruptive while it's underway?
How much the build affects daily life depends on where the ADU is being built. Standalone ADU projects are typically less disruptive, since work happens away from the main house. Projects that connect to the main structure may require temporary access during specific stages like framing or MEP rough-in. We provide advance notice about upcoming work and timelines.
Do I need to vacate the property during ADU construction?
In most cases, you do not need to vacate your main home 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 adu construction near San Jose ways that temporarily impact livability. Our construction supervisors will discuss these scenarios during the kickoff meeting.
How long will an ADU built through professional ADU construction remain in good condition?
Any ADU built to code with professional oversight should 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 comply with all local building codes to deliver a structure that stands the test of time.
ADU Construction for San Jose Homeowners
Residential areas across San Jose present a diverse mix of property types that are perfectly suited for ADU construction. Homeowners in the Willow Glen neighborhood often discover their properties work well for both attached and detached projects. Neighborhoods near Blossom Hill Road have seen growing ADU activity as multigenerational living becomes more common. From neighborhoods near the Guadalupe River Park corridor to those near Branham Lane, our team has likely worked nearby.
The City of San Jose's building department has developed specific protocols for ADU construction that experienced builders know well. Location near major arterials like Story Road or Tully Road can impact the design approach for a given ADU project. Our familiarity with the San Jose permitting environment means fewer surprises from the first meeting to the final inspection.
Start Your ADU Construction Assessment Today
Should you be thinking about how to add an ADU to your property, Brother & Brother Builders is here to help. We bring years of hands-on experience in ADU construction for many different project types — from modest studio builds to large custom detached cottages. Every project starts with a thorough and honest property review where we understand your vision and give you a realistic picture of what's achievable.
Get in touch with our office to schedule a site visit. No matter where you are in the decision-making process, our team is happy to discuss timelines, costs, and design possibilities 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 & Brother Builders | 3109 Stevens Creek Boulevard | San Jose CA 95117 | (888) 412-2632