Brother & Brother Builders

Transform Your Property with Expert ADU Construction

Families in San Jose, CA are finding that adding an accessory dwelling unit is one of the smartest investments they can make. ADU construction opens the door to a powerful new living space on your existing property — whether you want to house a family member. Brother & Brother Builders has guided hundreds of local homeowners bring these projects to life with craftsmanship and care.

The popularity of ADU construction has grown rapidly in recent years, and it's easy to understand why. California state law has simplified the process for homeowners to construct these secondary units, and local municipalities like San Jose have supported the trend as a way to expand the housing supply. Whether you want to build a detached backyard cottage, a garage conversion, or an attached addition, ADU construction offers greater control over how your property serves your household.

At Brother & Brother Builders, we apply deep hands-on experience to every ADU construction job. 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 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 planning, approving, and constructing an accessory dwelling unit on a residential property. An accessory dwelling unit is a complete living space here — equipped with a kitchen, bathroom, sleeping area, and its own access point — that sits on the same property as a primary residence. ADU construction includes various structural types, including detached backyard units, attached additions, garage conversions, and even below-grade dwelling units.

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 city for permit approval. Once the paperwork is cleared, ADU construction enters the physical build phase — which encompasses site preparation, framing, HVAC, drywall, flooring, and exterior finishes. The result is a fully functional living unit attached to or separate from your main home.

The difference between a good and a great ADU build is the depth of planning at every stage. Products need to be chosen to match the primary home's aesthetic. Systems like plumbing and electrical must be designed to handle full-time occupancy. Brother & Brother Builders approaches every build with the same high standards we use on major 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, generating steady monthly revenue for the homeowner.
• Space for Loved Ones — ADU construction provides adult children a comfortable home of their own without moving to another neighborhood.
• Customization Options — From modern studio layouts, ADU construction can be tailored to your specific needs.
• Faster Permitting in California — Recent state legislation has cut down the permitting obstacles associated with ADU construction, making the process that is faster and more affordable than ever before.
• Sustainable Land Use — Building an ADU works within your current footprint instead of expanding urban sprawl, which supports broader sustainability goals.
• Separate Entrances and Spaces — Unlike a bedroom addition, ADU construction creates a truly separate unit where residents have their own space.
• Durable Return on Investment — A well-built ADU holds its value for many years and generates both usable housing and equity growth.

The ADU Construction Journey Step by Step

1. Initial Property Assessment and Feasibility Review — Our experts review your property to analyze zoning rules, slope conditions, and available square footage. This phase answers exactly what can be built before any resources go toward planning.
2. Architectural Drafting and Space Planning — Experienced draftspeople create detailed floor plans based on your goals. Layouts are carefully considered to create practical, comfortable living.
3. Filing for Building Permits — ADU construction in San Jose involves filing drawings to the city's building department for inspection and clearance. Brother & Brother Builders coordinates the permitting on your behalf, addressing any city comments promptly.
4. Site Preparation and Foundation Work — Once permits are granted, physical construction begins. This involves leveling and prepping the ground, pouring the concrete foundation, and establishing utility connections.
5. Structural Framing and Weatherproofing — The structural frame is erected followed by weatherproofing and exterior finish materials. This phase, the ADU takes its visible shape.
6. Interior Systems and Infrastructure — Licensed subcontractors install the plumbing lines, electrical wiring, and HVAC systems that make the ADU ready for occupancy. Inspections are completed at required milestones throughout ADU construction.
7. Finishes, Fixtures, and Final Walkthrough — Countertops, hardware, finishes, and fixtures are installed and finished to your specifications. A final city inspection issues the certificate of occupancy 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 typically fall into a few recognizable groups. If you have a residential property with enough lot space to meet setback requirements, you're already in a good starting place. Homeowners hoping to offset mortgage costs through rental are among the most motivated ADU construction clients, along with families navigating multigenerational living situations.

You may also be someone who runs a small business and wants a detached creative or business space that remains away from your family's daily life. Landlords and real estate investors 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 lots that are below minimum size thresholds. Very small lots or properties with easements may need a modified approach. Our team can assess each property case by case to recommend the right path forward.

ADU Construction FAQ

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

The complete duration for ADU construction usually runs between six to fourteen months, influenced by the type of unit being built and city review schedules. Permitting alone can take a significant portion of the overall timeline in San Jose, so planning ahead matters. Simpler garage conversions often finish in the lower end of the range, while multi-room detached cottages fall toward the upper end of the timeline.

What does ADU construction usually run in terms of budget?

Budget requirements differ based on project complexity and finishes selected. Locally, ADU construction typically ranges from $150,000 to $400,000 or more for a detached new build. Interior conversion projects often come in under, sometimes starting around $80,000 depending on scope. A precise cost projection 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. Standalone ADU projects are generally the least intrusive, since the construction zone is separate. Interior conversions may create short-term inconveniences during key milestones. Our team communicates clearly about any phases that may affect your routine.

Do I need to vacate the property during ADU construction?

For the majority of homeowners, you are not required to vacate your house during ADU construction. The vast majority of projects are designed so that you remain on the property throughout the construction timeline. There are edge cases if major utility upgrades affect the main house in ways that require short-term access disruption. Our construction supervisors will discuss these scenarios during the pre-construction consultation.

How long will an ADU built through professional ADU construction last?

A well-built ADU should last as long as your primary home — often several decades with routine maintenance. Durability depends to the quality of materials used, how consistently minor repairs are addressed, and how proactively issues are resolved over time. We select residential-grade products rated for longevity and build to current California residential standards to ensure lasting performance.

ADU Construction for Local 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 have found their lots accommodate detached backyard units nicely. The Berryessa area are seeing more homeowners add secondary units as multigenerational living becomes more common. Whether your property is near downtown San Jose, our team has project experience in the area.

The City of San Jose's building department applies particular standards for ADU construction that require a builder familiar with local expectations. Proximity to transit corridors can impact the design approach for a given ADU project. Our team's knowledge of this region's building landscape 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 the team to call. Our builders provide years of hands-on experience in ADU construction across a wide range of project types — from simple garage conversions to fully independent secondary homes. Every project starts with a detailed, no-pressure consultation where we listen to your goals and share clear expectations of what the project will involve.

Reach out to our team to begin the conversation. Whether you're in the early stages of planning, we're glad to discuss timelines, costs, and design possibilities and give you the clarity you need to move forward. 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