Unlock New Space with Quality 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 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 guided hundreds of local homeowners bring these projects to life with precision and care.
The popularity of 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 address housing needs. If you're planning 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 job. Our team is familiar with city and county requirements, the engineering considerations, and the planning steps 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 describes the process of designing, permitting, and building 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 entryway — 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 interior space reconfigurations.
Mechanically, everything kicks off with a thorough property evaluation, where our team evaluate property boundaries, available square footage, and infrastructure capacity. From there, blueprints are prepared and submitted to the relevant municipal authority. Once permits are secured, ADU construction moves into the physical build phase — which covers everything from foundational work, framing, HVAC, drywall, flooring, and exterior finishes. The result is a completely finished living unit connected to or independent of 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 complement the existing structure. Systems like plumbing and electrical must be designed to handle full-time occupancy. Brother & Brother Builders treats each project with the same high standards we apply to large-scale custom home projects.
Key Benefits ADU Construction
- Increased Property Value — 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 may be listed as a long-term rental or short-term vacation unit, providing a consistent income stream for the homeowner.
- Multi-Generational Living — ADU construction gives aging parents a private, independent living space without leaving the property.
- Design Flexibility — From two-bedroom configurations, ADU construction is adaptable to your household's priorities.
- Faster Permitting in California — Recent state legislation has minimized 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 maximizes the land you already own instead of expanding urban sprawl, 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 holds its value for decades, providing both livable square footage and monetary benefit.
The ADU Construction Journey Step by Step
- Initial Property Assessment and Feasibility Review — Our experts review your property to evaluate setbacks, lot coverage limits, and utility connections. This phase answers exactly what's possible before any time is invested in drawings.
- Architectural Drafting and Space Planning — Licensed architects and designers create comprehensive blueprints based on your goals. Space is thoughtfully allocated to maximize function and livability.
- Permit Submission and Municipal Review — ADU construction in San Jose demands documentation to the city's building department for sign-off and verification. 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 involves leveling and prepping the ground, pouring the concrete foundation, and establishing utility connections.
- Shell Construction and Exterior Finishing — Walls and roof systems go up followed by weatherproofing and exterior finish materials. During this step, the ADU becomes recognizable as a structure.
- Mechanical, Electrical, and Plumbing Installation — Skilled tradespeople install the heating, cooling, drainage, and power infrastructure that make the ADU ready for occupancy. Every system is reviewed at designated stages throughout ADU construction.
- Interior Completion and City Sign-Off — Trim, appliances, tile, and lighting are fitted and completed to the agreed design. 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?
Property owners who are best suited from ADU construction often belong to a few common profiles. If you have a residential property with available square footage under zoning rules, you're already well-positioned. Homeowners looking to generate income through rental are among the most financially driven ADU construction clients, along with families accommodating adult children who need housing.
ADU construction also suits someone who needs a dedicated professional workspace and wants a detached creative or business space that remains away from your family's daily life. Landlords and real estate investors who want to maximize their land are also prime candidates for ADU construction, since rental income frequently offsets build costs.
Homeowners who may want to pause and evaluate include sites with unusual utility access challenges. Parcels in historic districts or HOA-restricted communities may face additional constraints. Our experts click here will evaluate each property case by case to provide realistic options.
ADU Construction FAQ
How long does ADU construction typically take from start to finish?
The total process for ADU construction commonly spans six to fourteen months, depending on design complexity and local permitting timelines. Permitting alone can take two to four months 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 usually run in terms of budget?
Costs vary widely based on the type and size of the ADU. Locally, ADU construction commonly costs $150,000 to $400,000 or more for a fully custom construction. Interior conversion projects often come in under, sometimes starting around $80,000 depending on scope. A detailed estimate can only be given after completing a full site assessment.
Is ADU construction disruptive while it's underway?
How much the build affects daily life depends on where the ADU is being built. New construction in the rear yard are usually easier to live alongside, since work happens away from the main house. Garage conversions or attached additions may involve some shared wall work during certain phases of construction. We provide advance notice about what to expect at each stage.
Do I need to leave my home during ADU construction?
Generally speaking, you won't have to vacate your primary residence during ADU construction. The vast majority of projects are structured to allow you stay in your primary unit throughout the build. Exceptions may arise if major utility upgrades affect the main house in ways that briefly affect habitability. Our project managers will flag these situations during the kickoff meeting.
How long will an ADU built through professional ADU construction hold up?
An ADU constructed with quality materials is designed 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, whether the unit is properly cared for, and how proactively issues are resolved over time. Our builds use commercial-grade materials and build to current California residential standards to protect your investment for the long haul.
ADU Construction for San Jose Homeowners
The communities throughout San Jose provide a variety of property types that are ideally positioned for ADU construction. Homeowners in the Willow Glen neighborhood have found their lots work well for both attached and detached projects. The Berryessa area are seeing more homeowners add secondary units as families expand. From neighborhoods near the Guadalupe River Park corridor to those near Branham Lane, our team knows the permitting landscape well.
The City of San Jose's building department follows defined procedures for ADU construction that experienced builders know well. Access to infrastructure along thoroughfares like Monterey Road can impact the design approach for a given ADU project. Our familiarity with these local conditions means smoother project delivery from the first meeting to the final inspection.
Schedule Your ADU Construction Consultation Today
Should you be thinking about how to explore what an ADU could look like on your lot, Brother & Brother Builders is here to help. We bring proven skills in ADU construction across a wide range of project types — from simple garage conversions to multi-room backyard residences. Our approach opens with a comprehensive site assessment where we learn what you're trying to accomplish and give you a realistic picture of what's achievable.
Get in touch with our office to set up your consultation. No matter where you are in the decision-making process, we enjoy answer questions, share examples of our work and make sure you feel confident before committing. 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