Everything You Need to Know About ADU Construction

Transform Your Property with Expert ADU Construction

Property owners throughout 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 versatile new living space on your existing property — whether you want to generate rental income. Brother & Brother Builders has supported hundreds of local homeowners see these visions to life with skill and integrity.

The demand for ADU construction has increased significantly in recent years, and it's easy to understand why. California state law now makes it easier for homeowners to construct these secondary units, and local municipalities like San Jose have encouraged 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 works.

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 requirements, and the planning steps that make an ADU truly livable. Should you want to learn about what ADU construction could do for your property, this guide covers everything you need to know.

What Is an ADU Build?

ADU construction describes 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 — including a kitchen, bathroom, sleeping area, and its own entryway — that is located on the same parcel as a primary residence. ADU construction can take several forms, including detached backyard units, attached additions, garage conversions, and even interior space reconfigurations.

Mechanically, everything kicks off with a detailed site assessment, where our builders evaluate setbacks, zoning, utility access, and structural feasibility. From there, architectural drawings are prepared and submitted to the local building department. Once the paperwork is cleared, ADU construction transitions to the physical build phase — which includes foundation work, framing, roofing, plumbing, electrical, insulation. The result is a fully functional living unit connected to or independent of your main home.

The difference between a good and a great ADU build is the attention to detail at every stage. Components should be specified to align with the neighborhood's character. Systems like plumbing and electrical must be sized for independent daily use. Brother & Brother Builders handles every ADU construction job with the same technical discipline we apply to large-scale custom home projects.

Key Benefits ADU Construction

• Higher Resale Potential — 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 is leasable as a long-term rental or short-term vacation unit, generating steady monthly revenue for the homeowner.
• Space for Loved Ones — ADU construction offers family members a self-contained residence without leaving the property.
• Design Flexibility — From modern studio layouts, ADU construction is adaptable to your specific needs.
• Simplified Regulatory Path — Recent state legislation has minimized the red tape associated with ADU construction, creating a path that is faster and more affordable than ever before.
• Efficient Use of Your Lot — Building an ADU works within your current footprint instead of consuming open land, which supports broader sustainability goals.
• Privacy for All Residents — Unlike a bedroom addition, ADU construction delivers a genuinely independent unit where occupants have full privacy.
• Long-Term Investment Security — A well-built ADU continues to produce returns for the long haul by offering both functional space and financial upside.

The ADU Construction Journey Step by Step

1. Property Walkthrough and Feasibility Check — Our builders assess your property to evaluate setbacks, lot coverage limits, and utility connections. This step tells you 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 requires submitting plans to the city's building department for review and approval. Our team handles all submissions on your behalf, responding to review feedback promptly.
4. Ground Prep and Structural Base — Once permits are approved, the build starts. This involves leveling and prepping the ground, laying the structural base, and running initial plumbing and electrical conduits.
5. Shell Construction and Exterior Finishing — The structural frame is erected followed by weatherproofing and exterior finish materials. At this stage, the ADU transforms from a concept to a building.
6. MEP Systems Rough-In — Skilled tradespeople install the heating, cooling, drainage, and power infrastructure that make the ADU ready for occupancy. All work is inspected at designated stages throughout ADU construction.
7. Interior Finishing and Final Inspections — Trim, appliances, tile, and lighting are installed and finished to the agreed design. A final city inspection issues the certificate of occupancy and your new space is cleared for use.

Who Is a Good Candidate for ADU Construction?

Property owners who are best suited from ADU construction often belong to a few common profiles. If you are a homeowner with available square footage under zoning rules, you're already a strong candidate. 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.

Another strong candidate is someone who needs a dedicated professional workspace and wants a separate office or studio space that is distinct from your family's daily life. Landlords and real estate investors who are building a portfolio are also well suited 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 face additional constraints. Our experts will evaluate each property on its own merits to recommend the right path forward.

ADU Construction FAQ

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

The full timeline for ADU construction commonly spans six to fourteen months, influenced by the type of unit being built and local permitting timelines. City get more info review on its own can take two to four months in San Jose, so beginning the process sooner rather than later is wise. Straightforward interior conversions can move faster, while larger new construction ADUs take longer to complete.

What does ADU construction typically cost?

Pricing depends on many factors based on the type and size of the ADU. Locally, ADU construction generally falls between $150,000 to $400,000 or more for a standalone backyard unit. Attached ADU additions often come in under, sometimes between $75,000 and $140,000. An accurate budget can only be given after completing a full site assessment.

Is ADU construction intrusive while it's underway?

How much the build affects daily life depends on where the ADU is being built. Detached backyard builds are generally the least intrusive, since the crew operates at a distance from your living areas. Interior conversions may require temporary access during key milestones. We provide advance notice 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 primary residence during ADU construction. Most builds are structured to allow you continue living in the home throughout the construction timeline. Certain situations could require a brief departure if major utility upgrades affect the main house in ways that temporarily impact livability. Our project managers will flag these situations during the kickoff meeting.

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

Any ADU built to code with professional oversight can be expected to last as long as the main residence — indefinitely with proper upkeep. How long it lasts comes down to the systems installed, whether the unit is properly cared for, and if mechanical components are maintained on schedule. 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 well suited for ADU construction. Homeowners in the Willow Glen neighborhood have found their lots work well for both attached and detached projects. Neighborhoods near Blossom Hill Road are increasingly popular for ADU construction as housing demand rises. 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 influence utility connection requirements for a given ADU project. Our familiarity with the San Jose permitting environment means fewer surprises from the first meeting to the final inspection.

Start Your ADU Construction Planning Session Today

If you're ready to add an ADU to your property, Brother & Brother Builders is ready to guide you. Our builders provide proven skills in ADU construction including all types of project types — from small attached additions to fully independent secondary homes. The process begins with a detailed, no-pressure consultation where we learn what you're trying to accomplish and provide an honest assessment 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 make sure you feel confident before committing. 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