Brother & Brother Builders

Expand Your Home with Quality ADU Construction

Property owners throughout San Jose, CA are finding that adding an accessory dwelling unit is one of the most rewarding investments they can make. ADU construction provides a flexible 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 skill and care.

The demand for ADU construction has increased significantly in recent years, and it's not hard to see why. California state law has simplified the process for homeowners to build these secondary units, and local municipalities like San Jose have encouraged the trend as a way to increase density responsibly. Whether you want to build a detached backyard cottage, a garage conversion, or an attached addition, ADU construction provides increased control over how your property functions.

At Brother & Brother Builders, we draw on extensive hands-on experience to every ADU construction job. Our team understands the local permitting process, the engineering considerations, and the design choices that make an ADU truly livable. Should you want to learn about what ADU construction could do for your property, this guide will walk you through everything you need to know.

What Is the ADU Construction Process?

ADU construction involves 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 includes various structural types, including detached backyard units, attached additions, garage conversions, and even basement or interior conversions.

Mechanically, the work starts with a comprehensive review of your lot, where our team evaluate property boundaries, available square footage, and infrastructure capacity. From there, architectural drawings are prepared and submitted to the relevant municipal authority. Once permits are secured, ADU construction transitions to the physical build phase — which covers everything from foundational work, framing, roofing, plumbing, electrical, insulation. The result is a completely finished living unit adjacent to or detached from your main home.

The difference between a good and a great ADU build is the level of craftsmanship at every stage. Products need to be chosen to match the primary home's aesthetic. 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 use on major custom home projects.

Key Benefits ADU Construction

• Increased Property Value — ADU construction contributes significant market value to your property, often increasing appraised value substantially when it's time to sell.
• Revenue Generation — A completed ADU is leasable 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 self-contained residence without moving to another neighborhood.
• Customization Options — From two-bedroom configurations, ADU construction may be customized to your household's priorities.
• Simplified Regulatory Path — Recent state legislation has cut down the barriers and delays associated with ADU construction, making the process that is faster and less expensive than ever before.
• Sustainable Land Use — Building an ADU uses your existing lot instead of consuming open land, which supports broader sustainability goals.
• Privacy for All Residents — Unlike a bedroom addition, ADU construction produces a fully self-contained unit where tenants live autonomously.
• Durable Return on Investment — A well-built ADU holds its value for decades, providing both usable housing and equity growth.

The ADU Construction Journey Step by Step

1. Initial Property Assessment and Feasibility Review — Our builders assess your property to analyze zoning rules, slope conditions, and available square footage. This stage clarifies exactly what can be built before any time is invested in drawings.
2. Custom Design and Architectural Planning — Our design team create precise architectural drawings tailored to your needs. Space is thoughtfully allocated to optimize daily use.
3. Filing for Building Permits — ADU construction in San Jose involves filing drawings to the city's building department for review and approval. Our team handles all submissions on your behalf, resolving any revision requests promptly.
4. Ground Prep and Structural Base — Once permits are issued, on-site work kicks off. This includes grading the site, completing foundation work, and setting up utilities.
5. Framing, Roofing, and Exterior Work — The structural frame is erected followed by insulation, sheathing, and exterior cladding. During this step, the ADU transforms from a concept to a building.
6. Interior Systems and Infrastructure — 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.
7. Interior Finishing and Final Inspections — Flooring, cabinetry, fixtures, paint are installed and finished to the approved plan. A last official inspection issues the certificate of occupancy and the unit is officially approved for use.

Who Is a Strong Candidate for ADU Construction?

People who see the greatest return from ADU construction generally fit within a few recognizable groups. If you are a homeowner with a backyard, garage, or basement that could be converted, you're already in a good starting place. 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 runs a small business and wants a private work environment that remains away from your family's daily life. Property investors and rental owners who want to maximize their land are also prime candidates 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. Parcels in historic districts or HOA-restricted communities may require additional review. Brother & Brother Builders reviews each property case by case to advise you on what's feasible.

ADU Construction FAQ

How long does ADU construction usually 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 how quickly approvals come through. The approval phase alone can take several months in San Jose, so planning ahead matters. Smaller detached units can move faster, while larger new construction ADUs fall toward the upper end of the timeline.

What does ADU construction typically cost?

Budget requirements differ based on whether it's a conversion or new construction. Locally, ADU construction commonly costs $150,000 to $400,000 or more for a standalone backyard unit. Attached ADU additions are generally priced lower, sometimes in the $80,000 to $150,000 range. An accurate budget can only be developed after a thorough property review.

Is ADU construction disruptive while it's underway?

How much the build affects daily life depends on where the ADU is being built. Detached backyard builds are usually easier to live alongside, since the crew operates at a distance from your living areas. Interior conversions may require temporary access during certain phases of construction. Our team communicates clearly about what to expect at each stage.

Do I need to leave my home during ADU construction?

In most cases, you do not need to vacate your primary residence during ADU construction. Most job sites are structured to allow you remain on the property throughout the build. Exceptions may arise if significant structural connections require temporary shutoffs 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 last?

A well-built ADU is designed to last as long as your primary home — typically 50 years or more. 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. Brother & Brother Builders specifies residential-grade products rated for longevity and follow all code requirements to deliver a structure that stands the test of time.

ADU Construction for Local Homeowners

San Jose's neighborhoods offer a wide range of property types that are ideally positioned 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 have seen growing ADU activity as multigenerational living becomes more common. Whether your property is more info near downtown San Jose, our team has likely worked nearby.

Local regulatory bodies in this area has developed specific protocols for ADU construction that experienced builders know well. Location near major arterials like Story Road or Tully Road can impact the design approach for a given ADU project. Brother & Brother Builders' experience across these local conditions means more accurate timelines and budgets from kickoff through certificate of occupancy.

Start Your ADU Construction Assessment Today

If you're ready to add an ADU to your property, Brother & Brother Builders is here to help. Our experts offer proven skills in ADU construction for many different project types — from small attached additions to large custom detached cottages. Our approach opens with a thorough and honest property review where we listen to your goals and provide an honest assessment of what's achievable.

Reach out to our team to schedule a site visit. Even if you're just exploring the idea, we're glad to answer questions, share examples of our work and give you the clarity you need to move forward. ADU construction is a significant investment — and our goal is to ensure it delivers real value.

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