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 house a family member. Brother & Brother Builders has helped hundreds of local homeowners see these visions to life with precision and transparency.
The demand for ADU construction has increased significantly in recent years, and it's easy to understand why. California state law has streamlined permitting for homeowners to build 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 click here conversion, or an attached addition, ADU construction provides increased control over how your property serves your household.
At Brother & Brother Builders, we apply deep hands-on experience to every ADU construction project. Our team is familiar with city and county requirements, the engineering considerations, and the aesthetic decisions that make an ADU truly livable. When you're ready to explore what ADU construction could look like on your property, this guide will walk you through 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 — equipped with a kitchen, bathroom, sleeping area, and its own entryway — 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, the work starts with a thorough property evaluation, where our team evaluate lot dimensions, existing structures, soil conditions, and local code requirements. From there, architectural drawings are prepared and submitted to the local building department. Once permits are secured, ADU construction moves into 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 adjacent to or detached from your main home.
What separates excellent ADU construction from an average project is the attention to detail at every stage. Products need to be chosen to align with the neighborhood's character. Systems like HVAC and drainage must be sized for independent daily use. Brother & Brother Builders handles every ADU construction job with the same professional rigor we bring to full custom home projects.
Key Reasons to Choose ADU Construction
- Increased Property Value — ADU construction adds measurable market value to your property, often generating strong equity gains when it's time to sell.
- Revenue Generation — A completed ADU may be listed as a long-term rental or short-term vacation unit, creating ongoing passive income for the homeowner.
- Multi-Generational Living — ADU construction gives aging parents a private, independent living space without leaving the property.
- Personalized Layouts — From modern studio layouts, ADU construction can be tailored 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 more cost-efficient than ever before.
- Efficient Use of Your Lot — Building an ADU maximizes the land you already own instead of consuming open land, which supports broader sustainability goals.
- Separate Entrances and Spaces — Unlike a bedroom addition, ADU construction delivers a genuinely independent unit where residents have their own space.
- Lasting Financial Benefit — A well-built ADU continues to produce returns for decades, providing both usable housing and equity growth.
The ADU Construction Process Step by Step
- Site Evaluation and Zoning Analysis — Our experts review your property to evaluate setbacks, lot coverage limits, and utility connections. This phase answers exactly what's possible before any resources go toward planning.
- Architectural Drafting and Space Planning — Our design team create comprehensive blueprints based on your goals. Space is thoughtfully allocated to create practical, comfortable living.
- Permitting and City Approval — ADU construction in San Jose demands documentation to the city's building department for review and approval. Our team handles all submissions on your behalf, addressing any city comments promptly.
- Ground Prep and Structural Base — Once permits are issued, the build starts. This involves leveling and prepping the ground, pouring the concrete foundation, and setting up utilities.
- Structural Framing and Weatherproofing — Walls and roof systems go up followed by weatherproofing and exterior finish materials. During this step, the ADU transforms from a concept to a building.
- Mechanical, Electrical, and Plumbing Installation — Skilled tradespeople install the plumbing lines, electrical wiring, and HVAC systems that make the ADU ready for occupancy. Every system is reviewed at required milestones throughout ADU construction.
- Interior Finishing and Final Inspections — Countertops, hardware, finishes, and fixtures are fitted and completed to your specifications. A final city inspection confirms the unit is code-compliant and the unit is officially approved for use.
Who Is a Good Candidate for ADU Construction?
Homeowners who benefit most from ADU construction generally fit within a few recognizable groups. If you own a single-family home with a backyard, garage, or basement that could be converted, you're already well-positioned. Homeowners wanting to add a revenue stream through rental are among the most motivated ADU construction clients, along with families navigating multigenerational living situations.
ADU construction also suits someone who runs a small business and wants a private work environment that remains away from your family's daily life. Real estate-minded homeowners who are building a portfolio are also a natural fit for ADU construction, since rental income frequently offsets build costs.
Homeowners who may want to pause and evaluate include lots that are below minimum size thresholds. Very small lots or properties with easements may require additional review. Our team can assess 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 usually runs between six to fourteen months, influenced by the type of unit being built and local permitting timelines. City review on its own can take two to four months in San Jose, so planning ahead matters. Smaller detached units can move faster, while larger new construction ADUs take longer to complete.
What does ADU construction cost in San Jose?
Costs vary widely based on project complexity and finishes selected. 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 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?
The day-to-day impact depends on whether you're converting existing space or building new. Detached backyard builds are generally the least intrusive, since the crew operates at a distance from your living areas. Garage conversions or attached additions may require temporary access during specific stages like framing or MEP rough-in. Our team communicates clearly about upcoming work and timelines.
Do I need to vacate the property during ADU construction?
For the majority of homeowners, you do not need to vacate your house during ADU construction. Most builds are designed so that you stay in your primary unit throughout the build. Exceptions may arise if interior conversion work touches shared systems 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?
Any ADU built to code with professional oversight should last as long as any standard residential structure — often several decades with routine maintenance. Longevity is tied to the standard of construction, whether the unit is properly cared for, and whether systems like roofing and plumbing are serviced regularly. We select high-quality components and build to current California residential standards to deliver a structure that stands the test of time.
ADU Construction for San Jose Homeowners
The communities throughout San Jose provide a variety of property types that are well suited for ADU construction. Residents in the Rose Garden district often discover their properties work well for both attached and detached projects. Neighborhoods near Blossom Hill Road 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 has developed specific protocols for ADU construction that require a builder familiar with local expectations. Location near major arterials like Story Road or Tully Road can affect how quickly permits are approved for a given ADU project. Our familiarity with the San Jose permitting environment means fewer surprises from design through the final walkthrough.
Book Your ADU Construction Assessment Today
If you're ready to move forward with ADU construction, Brother & Brother Builders is here to help. Our experts offer proven skills in ADU construction for many different project types — from simple garage conversions to fully independent secondary homes. Every project starts with a comprehensive site assessment where we understand your vision and provide an honest assessment of what ADU construction on your property will look like.
Reach out to our team to begin the conversation. Whether you're in the early stages of planning, our team is happy 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're committed to helping you get it right.
Brother & Brother Builders | 3109 Stevens Creek Boulevard | San Jose CA 95117 | (888) 412-2632