Accessory Dwelling Unit (ADU) Construction in the East Bay
For over 35 years, Abbes Construction has helped homeowners across Danville, Alamo, Walnut Creek, Lafayette, Moraga, Orinda, San Ramon, Pleasanton, Livermore, and Diablo add value, flexibility, and living space to their properties. Today, one of the most requested projects we build is the Accessory Dwelling Unit — commonly known as an ADU, in-law unit, granny flat, or backyard cottage.
Whether you're planning space for aging parents, a place for adult children, a long-term rental, or simply want to increase your property's value, our design-build team manages your ADU from initial concept through final inspection.
Why Build an ADU in the East Bay?
California's ADU legislation has made it significantly easier for homeowners to add secondary units to their property, and demand across Contra Costa and Alameda counties has grown accordingly. An ADU can serve as:
Multigenerational housing — a private, comfortable space for aging parents or adult children
Rental income — a long-term rental unit to offset your mortgage
Home office or studio — separated from the main house for privacy and focus
Guest space — for visiting family and friends
Long-term property value — added square footage and functionality that resonates with future buyers
Because ADU rules, lot requirements, and permitting pathways vary by city — and differ further in unincorporated areas like Alamo and Diablo, which are governed by Contra Costa County DCD rather than a city building department — working with a builder who already understands the local landscape saves time, money, and frustration.
Our ADU Services
Design & Planning We start with a site evaluation to understand your lot, setbacks, utility access, and any HOA or Specific Plan overlay considerations specific to your neighborhood. From there, we develop a design that fits both your goals and your property's constraints.
Permitting & Approvals Our team prepares and submits the plans required for ADU approval, coordinating with the relevant building department — whether that's a city planning office or, for Alamo and Diablo homeowners, the Contra Costa County DCD ePermits Center. We also manage any additional sign-offs required, such as fire district review for properties in wildland-urban interface zones.
Construction From foundation to final walkthrough, our in-house team and trusted subcontractors handle every phase: framing, electrical, plumbing, HVAC, insulation, drywall, and finish work — built to the same quality standard as our custom home projects.
Types of ADUs We Build
Detached ADUs — standalone backyard units, fully separate from the main home
Attached ADUs — additions connected to the primary residence
Garage conversion ADUs — transforming existing garage space into livable square footage
Junior ADUs (JADUs) — smaller units created within the existing footprint of the home, often with shared or separate entry
Our ADU Process
Consultation — We walk your property and discuss your goals, budget range, and timeline.
Design — Our team develops layout options suited to your lot and local requirements.
Permitting — We prepare and submit plans to the appropriate jurisdiction and manage the approval process.
Construction — Your dedicated project team builds your ADU with regular progress updates.
Final Walkthrough — We complete a full inspection with you before handing over the keys.
Areas We Serve
Abbes Construction builds ADUs throughout:
Danville · Alamo · Diablo · Walnut Creek · Lafayette · Moraga · Orinda · San Ramon · Pleasanton · Livermore
Frequently Asked Questions
What is an ADU? An ADU (Accessory Dwelling Unit) is a secondary, self-contained living space on a residential property. It can be detached, attached to the main home, or converted from existing space like a garage, and typically includes its own kitchen, bathroom, and separate entrance.
Do I need a permit to build an ADU? Yes. All ADUs require permit approval before construction begins. The process and reviewing agency depend on your city — homeowners in Alamo and Diablo work with Contra Costa County's Department of Conservation and Development, while those in incorporated cities like Danville, Walnut Creek, or San Ramon work directly with their city's building department.
Can I rent out my ADU? In most East Bay jurisdictions, ADUs can be rented long-term. Short-term rental rules vary by city, so it's worth confirming current local ordinances before planning a rental strategy.
How is building an ADU different from a home addition? An ADU is a separate, independently functioning living unit with its own kitchen and bathroom, while a standard addition typically expands the existing home without creating a self-contained unit. ADUs are also subject to distinct state and local regulations that don't apply to standard additions.
Does my lot qualify for an ADU? Most residential lots in the East Bay qualify for at least one ADU, though specifics depend on lot size, existing structures, and local zoning. A site evaluation is the best way to confirm what's possible on your property.
How long does it take to build an ADU? Timelines vary based on design complexity, permitting requirements, and project scope. We provide a project-specific timeline estimate after your initial consultation.
What does an ADU cost to build? Cost depends on size, finish level, site conditions, and whether the unit is detached, attached, or a conversion. We provide a detailed estimate based on your specific goals during the consultation phase.
We build custom homes throughout the East Bay, including
Danville, Alamo, Lafayette, Orinda, Walnut Creek, Moraga, Diablo, San Ramon, Pleasanton, and Livermore.