Brother & Brother Builders

Unlock New Space with Professional ADU Construction

Property owners throughout San Jose, CA are realizing that adding an accessory dwelling unit is one of the smartest investments they can make. ADU construction creates a versatile new living space on your existing property — whether you want to create a private workspace. Brother & Brother Builders has supported hundreds of local homeowners bring these projects to life with craftsmanship and transparency.

The popularity of ADU construction has increased significantly in recent years, and it's no mystery. California state law has streamlined permitting for homeowners to add these secondary units, and local municipalities like San Jose have supported the trend as a way to increase density responsibly. 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 apply deep hands-on experience to every ADU construction job. Our team is familiar with city and county requirements, the engineering considerations, and the planning steps that make an ADU beautiful. If you've been thinking about what ADU construction could mean for your property, this guide explains everything you need to know.

What Is ADU Construction?

ADU construction refers to the process of engineering, filing for, and completing an accessory dwelling unit on a residential property. An accessory dwelling unit is a fully independent living space — equipped with a kitchen, bathroom, sleeping area, and its own entryway — 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 basement or interior conversions.

Mechanically, the process begins with a comprehensive review of your lot, 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 approvals are in place, ADU construction enters the physical build phase — which includes foundation work, framing, roofing, plumbing, electrical, insulation. The result is a fully functional living unit adjacent to or detached from your main home.

What sets quality ADU construction apart is the level of craftsmanship at every stage. Materials must be selected to match the primary home's aesthetic. Systems like wiring and water supply must be sized for independent daily use. Brother & Brother Builders approaches every build with the same technical discipline we use on major custom home projects.

Key Reasons to Choose 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.
• 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 comfortable home of their own without leaving the property.
• Personalized Layouts — From open-plan one-bedrooms, ADU construction may be customized to your specific needs.
• Faster Permitting in California — Recent state legislation has minimized the permitting obstacles associated with ADU construction, creating a path that is faster and less expensive than ever before.
• Responsible Property Development — Building an ADU uses your existing lot instead of requiring new development, which supports broader sustainability goals.
• Separate Entrances and Spaces — Unlike a bedroom addition, ADU construction produces a fully self-contained unit where residents have their own space.
• Lasting Financial Benefit — A well-built ADU remains an asset for many years and generates both functional space and financial upside.

The ADU Construction Journey Step by Step

1. Initial Property Assessment and Feasibility Review — Our team visits your property to determine what type of ADU is allowed and where it can be placed. This step tells you exactly what's possible before any time is invested in drawings.
2. Blueprint Development and Layout Design — Experienced draftspeople create detailed floor plans tailored to your needs. Every square foot is planned to create practical, comfortable living.
3. Permitting and City Approval — ADU construction in San Jose requires submitting plans to the city's building department for sign-off and verification. We manage this entire process on your behalf, resolving any revision requests promptly.
4. Site Preparation and Foundation Work — Once permits are approved, physical construction begins. This involves leveling and prepping the ground, completing foundation work, and running initial plumbing and electrical conduits.
5. Shell Construction and Exterior Finishing — Walls and roof systems go up followed by insulation, sheathing, and exterior cladding. This phase, the ADU takes its visible shape.
6. MEP Systems Rough-In — Certified technicians install the heating, cooling, drainage, and power infrastructure that make the ADU fully functional. 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 approved plan. A last official inspection confirms the unit is code-compliant and your new space is cleared for use.

Who Is a Good Candidate for ADU Construction?

Homeowners who benefit most from ADU construction typically fall into a few clear categories. If you are a homeowner with a backyard, garage, or basement that could be converted, you're already a strong candidate. Homeowners hoping to offset mortgage costs through rental are among the most motivated ADU construction clients, along with families accommodating adult children who need housing.

ADU construction also suits someone who works from home and wants a separate office or studio space that remains away from your family's daily life. Property investors and rental owners who want to maximize their land are also a natural fit for ADU construction, since the return on investment is well-documented.

Homeowners who may want to pause and evaluate include sites with unusual utility access challenges. Sites with underground infrastructure conflicts may need a modified approach. Our experts will evaluate each property individually and honestly to recommend the right path forward.

ADU Construction Frequently Asked Questions

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

The complete duration for ADU construction typically ranges from six to fourteen months, depending on design complexity and how quickly approvals come through. The approval phase alone can take several months in San Jose, so planning ahead matters. Simpler garage conversions often finish in the lower end of the range, while custom detached builds fall toward the upper end of the timeline.

What does ADU construction usually run in terms of budget?

Pricing depends on many factors based on project complexity and finishes selected. In the San Jose area, ADU construction commonly costs $150,000 to $400,000 or more for a detached new build. Interior conversion projects are generally priced lower, sometimes in the $80,000 to $150,000 range. A detailed estimate can only be produced following a thorough property review.

Is ADU construction difficult to live through 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. Interior conversions may require temporary access during key milestones. Brother & Brother Builders keeps you informed about upcoming work and timelines.

Do I need to leave my home during ADU construction?

In most cases, you do not need to vacate your house during ADU construction. The vast majority of projects are designed so that you stay in your primary unit throughout the process. There are edge cases if significant structural connections require temporary shutoffs in ways that require short-term access disruption. Our project managers will discuss these scenarios during the pre-construction consultation.

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

A well-built ADU should last as long as your primary home — indefinitely with proper upkeep. Durability depends to the systems installed, how well routine maintenance is performed, and how proactively issues are resolved over time. We select high-quality components and comply with all local building codes to deliver a structure that stands the test of time.

ADU Construction for Local Homeowners

Residential areas across San Jose present a variety of property types that are perfectly suited for ADU construction. adu construction San Jose CA Homeowners in the Willow Glen neighborhood have found their lots work well for both attached and detached projects. The Berryessa area are increasingly popular for ADU construction as families expand. From neighborhoods near the Guadalupe River Park corridor to those near Branham Lane, our team has likely worked nearby.

San Jose's permitting office has developed specific protocols 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 this region's building landscape 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 here to help. Our builders provide years of hands-on experience in ADU construction across a wide range of project types — from modest studio builds to fully independent secondary homes. Our approach opens 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. No matter where you are in the decision-making process, we enjoy walk through your options, review completed projects and give you the clarity you need to move forward. ADU construction is a significant investment — and we want to make sure it's the right one for you.

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