Bayside Builders Group is a licensed Bay Area ADU contractor with 25+ years of experience. Services include detached ADUs, garage conversions, and in-law suites. Serving Oakland, San Jose, San Francisco, and surrounding counties.
read more
ProStruct Engineering offers ADU structural engineering services across California, providing permit-ready plans and calculations for detached ADUs, garage conversions, granny flats, and more, with a 2–3 week turnaround.
read more
ASL Remodeling is a California licensed ADU contractor (CSLB #1060310) with 20+ years experience and 300+ completed projects. Services include detached ADUs, garage conversions, granny flats, JADUs, and in-law suites with full design-build support.
read more
prefabADU is a Bay Area ADU builder with 16+ years of experience offering affordable kits and plans from under $45K. With 12 state-approved plans valid across California, they simplify permits, design, and installation for homeowners.
read more
ADBC Architecture completed an 800 SF detached ADU in East Bay, CA in 2025, designed for multigenerational living. Built with thermally modified wood and steel, the backyard cottage features high ceilings and large windows for a spacious feel.
read more
ADUs add rental income & property value. Services include garage conversions, detached ADUs, JADUs & granny flats. ADU Feasibility Studies cover code, utilities & ROI. Architectural services via Adapt Dwellings ensure smooth approval to construction.
read more
ADU Builders Bay Area specializes in detached ADUs, garage conversions, in-law suites & more. Expert ADU contractors offering transparent pricing, full permitting & quality construction throughout the Bay Area.
read more
Decor Builders is a San Jose-based ADU contractor with 15+ years of Bay Area experience. They offer full-service ADU design and construction, including granny flats and in-law suites, handling permits, engineering, and project management.
read more
Metricon Homes offers ADU construction and garage conversion services. Choose from 5 sizes: Marigold, Camellia, Magnolia, Dahlia, and Sunflower. Their Design to Doorstep process covers custom design to completion. Licensed contractor: Tobin Brinker, License #1128717.
read more
Apex ADU Builders is a Los Angeles-based contractor specializing in accessory dwelling unit construction. Services include new builds, garage conversions, permitting, and design. Costs range from $80K–$400K, with potential ROI 35% higher than homes without ADUs.
read more
Anura Design specializes in ADU design, offering styles from modern farmhouse and contemporary steel to Mediterranean stucco. Their interiors feature open-concept layouts, natural wood tones, and refined finishes tailored to compact, functional living spaces.
read more
Jeff Martinez Construction Inc. builds ADUs in Oakley, CA with 27+ years of experience. Services include detached ADUs, garage conversions, permits, finishing, and landscape integration across Contra Costa County.
read more
Urban Shore Builders offers full-service ADU design & construction, including garage conversions, detached units & additions. As a turnkey ADU contractor, they handle permits, design & build. Services include plumbing, electrical, HVAC & retaining walls.
read more
Collins Remodeling is a licensed ADU contractor in Alameda, CA, specializing in detached ADUs, garage conversions, JADUs, and granny flats. They manage permitting, design, and construction, helping homeowners add value and rental income.
read moreCastro Valley is a unique location for ADU construction because it is an unincorporated community governed by Alameda County rather than an independent city. This means that homeowners looking to build an Accessory Dwelling Unit must work with the Alameda County Planning Department and follow Alameda County's specific zoning codes and building regulations. Experienced ADU contractors in Castro Valley understand this distinction and are well-versed in navigating county-level permitting processes, which differ significantly from those of neighboring incorporated cities like San Leandro or Hayward.
Because Castro Valley falls under Alameda County jurisdiction, ADU contractors must comply with the county's ADU ordinance, which aligns with California state law but includes local nuances. Some important regulatory considerations include:
Hiring a contractor with direct experience in Castro Valley and Alameda County is essential for a smooth ADU project. Local ADU contractors are familiar with the Alameda County Building Services Agency, which handles permit applications, inspections, and plan checks. They understand the typical timelines, required documentation, and how to address common issues that arise during the approval process. Castro Valley's hillside terrain in many neighborhoods also presents unique grading and foundation challenges that experienced local contractors are equipped to handle.
Castro Valley homeowners are increasingly choosing ADUs to address the Bay Area's housing demand and to generate rental income. The most popular ADU types in the area include:
Working with a qualified ADU contractor in Castro Valley ensures your project meets all Alameda County requirements while maximizing your property's potential. From initial design and permitting through final inspection, the right contractor will guide you every step of the way, helping you add value to your home in one of the East Bay's most desirable communities.