Everything You Need to Know About ADU Construction

Transform Your Property with Quality 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 provides a versatile new living space on your existing property — whether you want to house a family member. Brother & Brother Builders has supported hundreds of local homeowners bring these projects to life with craftsmanship and transparency.

The demand for ADU construction has surged 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 supported 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 build. Our team is familiar with city and county requirements, the engineering considerations, and the aesthetic decisions that make an ADU functional. Should you want to learn about what ADU construction could do for your property, this guide explains everything you need to know.

What Is an ADU Build?

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 self-contained living space — featuring a kitchen, bathroom, sleeping area, and its own access point — that is located on the same parcel as a primary residence. ADU construction comes in multiple configurations, including detached backyard units, attached additions, garage conversions, and even interior space reconfigurations.

Mechanically, the work starts with a comprehensive review of your lot, where our professionals evaluate setbacks, zoning, utility access, and structural feasibility. From there, blueprints are prepared and submitted to the local building department. Once the paperwork is cleared, ADU construction moves into the physical build phase — which encompasses site preparation, framing, mechanical systems, weatherproofing, and interior finishing. The result is a fully functional living unit connected to or independent of your main home.

What separates excellent ADU construction from an average project is the depth of planning at every stage. Products need to be chosen to complement the existing structure. Systems like wiring and water supply must be sized for independent daily use. Brother & Brother Builders treats each project with the same high standards we use on major custom home projects.

Key Benefits ADU Construction

• Increased Property Value — 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 may be listed as a long-term rental or short-term vacation unit, providing a consistent income stream for the homeowner.
• Multi-Generational Living — ADU construction provides adult children a comfortable home of their own without moving to another neighborhood.
• Customization Options — From two-bedroom configurations, ADU construction may be customized to the intended occupant's lifestyle.
• Simplified Regulatory Path — Recent state legislation has reduced the barriers and delays associated with ADU construction, making the process that is faster and more affordable than ever before.
• Sustainable Land Use — Building an ADU uses your existing lot instead of requiring new development, which contributes to sustainability goals.
• Independent Living Areas — Unlike a bedroom addition, ADU construction delivers a genuinely independent unit where tenants live autonomously.
• Lasting Financial Benefit — 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 phase answers exactly what can be built before any resources go toward planning.
2. Custom Design and Architectural Planning — Our design team create comprehensive blueprints based on your goals. Layouts are carefully considered to maximize function and livability.
3. Permit Submission and Municipal Review — ADU construction in San Jose requires submitting plans to the city's building department for inspection and clearance. Brother & Brother Builders coordinates the permitting on your behalf, responding to review feedback promptly.
4. Ground Prep and Structural Base — Once permits are approved, on-site work kicks off. This involves leveling and prepping the ground, completing foundation work, and running initial plumbing and electrical conduits.
5. Framing, Roofing, and Exterior Work — Framing is completed followed by insulation, sheathing, and exterior cladding. This phase, the ADU becomes recognizable as a structure.
6. MEP Systems Rough-In — Licensed subcontractors install the plumbing lines, electrical wiring, and HVAC systems that make the ADU ready for occupancy. All work is inspected at required milestones throughout ADU construction.
7. Interior Finishing and Final Inspections — Countertops, hardware, finishes, and fixtures are installed and finished to the agreed design. A last official inspection grants legal occupancy status and the unit is officially approved for use.

Who Is a Right Fit for ADU Construction?

Property owners who are best suited from ADU construction typically fall into a few clear categories. If you own a single-family home with enough lot space to meet setback requirements, you're already a strong candidate. Homeowners wanting to add a revenue stream through rental are among the most motivated ADU construction clients, along with families supporting elderly parents.

You may also be someone who works from home and wants a separate office or studio space that is distinct from your family's daily life. Real estate-minded homeowners who want to maximize their land are also well suited for ADU construction, since rental income frequently offsets build costs.

Those who should discuss alternatives first include lots that are below minimum size thresholds. Parcels in historic districts or HOA-restricted communities may need a modified approach. Our experts will evaluate each property case by case to provide realistic options.

ADU Construction Frequently Asked Questions

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

The total process for ADU construction usually runs between six to fourteen months, based on the project scope and how quickly approvals come through. The approval phase alone can take two to four months in San Jose, so beginning the process sooner rather than later is wise. Smaller detached units can move faster, while custom detached builds take longer to complete.

What does ADU construction typically cost?

Pricing depends on many factors based on the type and size of the ADU. In the San Jose area, ADU construction commonly costs $150,000 to $400,000 or more for a fully custom construction. Garage conversions often come in under, sometimes in the $80,000 to $150,000 range. An accurate budget can only be produced following a formal feasibility evaluation.

Is ADU construction disruptive while it's underway?

The day-to-day impact depends on the project's location on your property. New construction in the rear yard are generally the least intrusive, 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 key milestones. Brother & Brother Builders keeps you informed about what to expect at each stage.

Do I need to vacate the property during ADU construction?

In most cases, you won't have to vacate your main home during ADU construction. Most builds 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 temporarily impact livability. Our project managers will discuss these scenarios during the planning phase.

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

Any ADU built to code with professional oversight is designed to last as long as any standard residential structure — typically here 50 years or more. Durability depends to the systems installed, how consistently minor repairs are addressed, and whether systems like roofing and plumbing are serviced regularly. Our builds use commercial-grade materials 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. Homeowners in the Willow Glen neighborhood frequently see their parcels work well for both attached and detached projects. 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 project experience in the area.

Local regulatory bodies in this area applies particular standards for ADU construction that experienced builders know well. 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 Assessment Today

When you want to add an ADU to your property, Brother & Brother Builders is here to help. Our builders provide licensed expertise in ADU construction across a wide range of project types — from simple garage conversions to fully independent secondary homes. The process begins with a thorough and honest property review where we understand your vision and provide an honest assessment of what's achievable.

Contact Brother & Brother Builders to schedule a site visit. Even if you're just exploring the idea, we're glad to walk through your options, review completed projects and make sure you feel confident before committing. This type of project is a meaningful commitment — and we're committed to helping you get it right.

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