Brother & Brother Builders

Transform Your Property with Professional 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 supported hundreds of local homeowners turn these plans to life with craftsmanship and care.

The demand for ADU construction has grown rapidly in recent years, and it's not hard to see why. California state law has streamlined permitting for homeowners to construct these secondary units, and local municipalities like San Jose have encouraged the trend as a way to expand the housing supply. If you're planning 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 draw on extensive hands-on experience to every ADU construction job. Our team knows the San Jose building codes, the engineering considerations, and the aesthetic decisions that make an ADU functional. If you've been thinking about what ADU construction could look like on your property, this guide covers everything you need to know.

What Is ADU Construction?

ADU construction refers to the process of designing, permitting, and building 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 entrance — that exists on the same website lot as a primary residence. ADU construction can take several forms, including detached backyard units, attached additions, garage conversions, and even basement or interior conversions.

Mechanically, the work starts with a detailed site assessment, where our team evaluate property boundaries, available square footage, and infrastructure capacity. From there, design plans are prepared and submitted to the local building department. Once approvals are in place, ADU construction enters the physical build phase — which encompasses site preparation, framing, mechanical systems, weatherproofing, and interior finishing. The result is a completely finished living unit adjacent to or detached from your main home.

What sets quality ADU construction apart is the level of craftsmanship at every stage. Components should be specified to complement the existing structure. Systems like wiring and water supply must be built for long-term residential demand. 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 contributes significant market value to your property, often generating strong equity gains when it's time to sell.
• Revenue Generation — A completed ADU can be rented as a long-term rental or short-term vacation unit, creating ongoing passive income for the homeowner.
• Multi-Generational Living — ADU construction provides adult children a private, independent living space without leaving the property.
• Customization Options — From modern studio layouts, ADU construction is adaptable to your specific needs.
• Faster Permitting in California — Recent state legislation has minimized the permitting obstacles associated with ADU construction, creating a path that is faster and more affordable than ever before.
• Responsible Property Development — Building an ADU works within your current footprint instead of consuming open land, which supports broader sustainability goals.
• Independent Living Areas — Unlike a bedroom addition, ADU construction produces a fully self-contained unit where tenants live autonomously.
• Long-Term Investment Security — A well-built ADU continues to produce returns for many years and generates both usable housing and equity growth.

The ADU Construction Procedure Step by Step

1. Site Evaluation and Zoning Analysis — Our team visits your property to evaluate setbacks, lot coverage limits, and utility connections. This stage clarifies exactly what's possible before any resources go toward planning.
2. Architectural Drafting and Space Planning — Licensed architects and designers create comprehensive blueprints reflecting your priorities. Layouts are carefully considered to create practical, comfortable living.
3. Filing for Building Permits — ADU construction in San Jose demands documentation to the city's building department for review and approval. We manage this entire process on your behalf, addressing any city comments promptly.
4. Excavation and Foundation Installation — Once permits are issued, the build starts. This includes grading the site, pouring the concrete foundation, and running initial plumbing and electrical conduits.
5. Framing, Roofing, and Exterior Work — Framing is completed followed by weatherproofing and exterior finish materials. This phase, the ADU transforms from a concept to a building.
6. Interior Systems and Infrastructure — Skilled tradespeople install the plumbing lines, electrical wiring, and HVAC systems that make the ADU ready for occupancy. All work is inspected at each code checkpoint throughout ADU construction.
7. Finishes, Fixtures, and Final Walkthrough — Countertops, hardware, finishes, and fixtures are placed and inspected to the agreed design. A last official inspection grants legal occupancy status and your new space is cleared for use.

Who Is a Strong Candidate for ADU Construction?

People who see the greatest return from ADU construction generally fit within a few recognizable groups. If you are a homeowner 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.

Another strong candidate is someone who runs a small business and wants a detached creative or business space that remains away from your family's daily life. Real estate-minded homeowners who already own residential properties are also well suited for ADU construction, since rental income frequently offsets build costs.

Situations where ADU construction may not be the best first step include properties with significant setback limitations. Sites with underground infrastructure conflicts may face additional constraints. Our experts will evaluate each property on its own merits to provide realistic options.

ADU Construction FAQ

How long does ADU construction typically take from start to finish?

The full timeline for ADU construction commonly spans 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 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 typically cost?

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 fully custom construction. Garage conversions are generally priced lower, sometimes in the $80,000 to $150,000 range. A detailed estimate can only be produced following a full site assessment.

Is ADU construction disruptive while it's underway?

The day-to-day impact depends on where the ADU is being built. Standalone ADU projects are generally the least intrusive, since the construction zone is separate. Interior conversions may create short-term inconveniences during certain phases of construction. Brother & Brother Builders keeps you informed about upcoming work and timelines.

Do I need to leave my home during ADU construction?

For the majority of homeowners, you won't have to vacate your primary residence during ADU construction. The vast majority of projects are structured to allow you continue living in the home throughout the construction timeline. There are edge cases if major utility upgrades affect the main house in ways that temporarily impact livability. Our construction supervisors will flag these situations during the pre-construction consultation.

How long will an ADU built through professional ADU construction remain in good condition?

A well-built ADU should last as long as your primary home — typically 50 years or more. Durability depends to the quality of materials used, how consistently minor repairs are addressed, and whether systems like roofing and plumbing are serviced regularly. Our builds use high-quality components and comply with all local building codes to ensure lasting performance.

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 frequently see their parcels are well configured for ADU builds. Communities around the Capitol Expressway corridor are increasingly popular for ADU construction as housing demand rises. If you're located closer to Evergreen, our team has likely worked nearby.

San Jose's permitting office has developed specific protocols for ADU construction that require a builder familiar with local expectations. Access to infrastructure along thoroughfares like Monterey Road can affect how quickly permits are approved for a given ADU project. Our familiarity with these local conditions means more accurate timelines and budgets from the first meeting to the final inspection.

Start Your ADU Construction Consultation Today

When you want to explore what an ADU could look like on your lot, Brother & Brother Builders is ready to guide you. Our builders provide proven skills in ADU construction including all types of project types — from simple garage conversions to fully independent secondary homes. The process begins with a thorough and honest property review where we learn what you're trying to accomplish and give you a realistic picture of what the project will involve.

Get in touch with our office to set up your consultation. Even if you're just exploring the idea, we're glad to answer questions, share examples of our work and give you the clarity you need to move forward. Building an ADU is a major decision — and we want to make sure it's the right one for you.

Brother & Brother Builders | 3109 Stevens Creek Boulevard | San Jose CA 95117 | (888) 412-2632