Transform Your Property with Quality ADU Construction
Families in San Jose, CA are discovering that adding an accessory dwelling unit is one of the most practical investments they can make. ADU construction provides a versatile new living space on your existing property — whether you want to create a private workspace. Brother & Brother Builders has helped hundreds of local homeowners see these visions to life with precision and transparency.
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 embraced the trend as a way to address housing needs. Whether you're building a detached backyard cottage, a garage conversion, or an attached addition, ADU construction gives you more control over how your property works.
At Brother & Brother Builders, we draw on extensive hands-on experience to every ADU construction project. Our team is familiar with city and county requirements, the engineering considerations, and the planning steps that make an ADU functional. If you've been thinking about what ADU construction could look like on your property, this guide explains everything you need to know.
What Is ADU Construction?
ADU construction involves 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, here and its own entryway — that is located on the same parcel as a primary residence. ADU construction includes various structural types, including detached backyard units, attached additions, garage conversions, and even basement or interior conversions.
Mechanically, the process begins with a detailed site assessment, where our professionals evaluate lot dimensions, existing structures, soil conditions, and local code requirements. From there, architectural drawings are prepared and submitted to the city for permit approval. Once permits are secured, ADU construction transitions to the physical build phase — which covers everything from foundational work, framing, mechanical systems, weatherproofing, and interior finishing. 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 attention to detail at every stage. Materials must be selected to match the primary home's aesthetic. Systems like plumbing and electrical 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 Advantages ADU Construction
- Increased Property Value — ADU construction adds measurable market value to your property, often returning more than the build cost when it's time to sell.
- Revenue Generation — 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 self-contained residence without moving to another neighborhood.
- Design Flexibility — From open-plan one-bedrooms, ADU construction is adaptable to your household's priorities.
- Streamlined Approval Process — Recent state legislation has reduced the barriers and delays associated with ADU construction, creating a path that is faster and more affordable than ever before.
- Sustainable Land Use — Building an ADU maximizes the land you already own instead of expanding urban sprawl, which aligns with sustainability goals.
- Separate Entrances and Spaces — Unlike a bedroom addition, ADU construction creates a truly separate unit where tenants live autonomously.
- Lasting Financial Benefit — A well-built ADU continues to produce returns for decades, providing both functional space and financial upside.
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 step tells you exactly what ADU types will work before any time is invested in drawings.
- Blueprint Development and Layout Design — Licensed architects and designers create detailed floor plans reflecting your priorities. Space is thoughtfully allocated to create practical, comfortable living.
- Permit Submission and Municipal Review — ADU construction in San Jose requires submitting plans to the city's building department for review and approval. Brother & Brother Builders coordinates the permitting on your behalf, addressing any city comments promptly.
- Ground Prep and Structural Base — Once permits are issued, on-site work kicks off. This covers land preparation, pouring the concrete foundation, and running initial plumbing and electrical conduits.
- Shell Construction and Exterior Finishing — The structural frame is erected followed by weatherproofing and exterior finish materials. During this step, the ADU becomes recognizable as a structure.
- Mechanical, Electrical, and Plumbing Installation — Certified technicians 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.
- Interior Completion and City Sign-Off — Trim, appliances, tile, and lighting are installed and finished to your specifications. A closing municipal review confirms the unit is code-compliant and the ADU is ready for use.
Who Is a Good Candidate for ADU Construction?
Property owners who are best suited from ADU construction often belong to a few recognizable groups. If you own a single-family home with available square footage under zoning rules, you're already in a good starting place. Homeowners wanting to add a revenue stream through rental are among the most motivated ADU construction clients, along with families accommodating adult children who need housing.
You may also be someone who runs a small business and wants a separate office or studio space that remains away from your family's daily life. Property investors and rental owners who are building a portfolio are also well suited for ADU construction, since the return on investment is well-documented.
Those who should discuss alternatives first include properties with significant setback limitations. Very small lots or properties with easements may face additional constraints. Brother & Brother Builders reviews each property on its own merits to provide realistic options.
ADU Construction FAQ
How long does ADU construction generally take from start to finish?
The total process for ADU construction commonly spans six to fourteen months, influenced by the type of unit being built and city review schedules. The approval phase alone can take two to four months in San Jose, so starting early is important. Smaller detached units may complete more quickly, while multi-room detached cottages fall toward the upper end of the timeline.
What does ADU construction usually run in terms of budget?
Costs vary widely based on whether it's a conversion or new construction. For most projects in this region, ADU construction typically ranges from $150,000 to $400,000 or more for a detached new build. Attached ADU additions are generally priced lower, sometimes between $75,000 and $140,000. A precise cost projection can only be given after completing a thorough property review.
Is ADU construction disruptive while it's underway?
The day-to-day impact depends on whether you're converting existing space or building new. New construction in the rear yard are usually easier to live alongside, since the crew operates at a distance from your living areas. Projects that connect to the main structure may involve some shared wall work during certain phases of construction. Our team communicates clearly about what to expect at each stage.
Do I need to move out during ADU construction?
In most cases, you do not need to vacate your main home during ADU construction. The vast majority of projects are set up to let you continue living in the home throughout the construction timeline. Certain situations could require a brief departure if significant structural connections require temporary shutoffs in ways that briefly affect habitability. The team at Brother & Brother Builders will walk you through any potential disruptions during the planning phase.
How long will an ADU built through professional ADU construction remain in good condition?
A well-built ADU should last as long as any standard residential structure — typically 50 years or more. Longevity is tied to the quality of materials used, whether the unit is properly cared for, and how proactively issues are resolved over time. We select commercial-grade materials and comply with all local building codes to ensure lasting performance.
ADU Construction for San Jose Homeowners
Residential areas across San Jose present a diverse mix of property types that are well suited for ADU construction. Homeowners in the Willow Glen neighborhood frequently see their parcels accommodate detached backyard units nicely. Neighborhoods near Blossom Hill Road are increasingly popular for ADU construction as housing demand rises. If you're located closer to Evergreen, our team has likely worked nearby.
Local regulatory bodies in this area follows defined procedures for ADU construction that our team navigates routinely. Location near major arterials like Story Road or Tully Road can impact the design approach 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
If you're ready to add an ADU to your property, Brother & Brother Builders is here to help. Our builders provide proven skills in ADU construction including all types of project types — from modest studio builds to multi-room backyard residences. Our approach opens with a detailed, no-pressure consultation 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. Whether you're in the early stages of planning, our team is happy to answer questions, share examples of our work and help you take the next step. This type of project is a meaningful commitment — and our goal is to ensure it delivers real value.
Brother & Brother Builders | 3109 Stevens Creek Boulevard | San Jose CA 95117 | (888) 412-2632