Areas we serve

Contra Costa County

Build a Custom Prefab ADU or Home in Contra Costa County

Whether you're planning an ADU for family, creating rental income, supporting multigenerational living, or building a new single-family home, Perpetual Homes designs and builds highly customizable prefab homes throughout California. Our streamlined process combines expert planning, engineering, permitting, and construction to make building simpler from start to finish.

ADU Regulations & Permitting in Contra Costa County

Contra Costa County follows California's statewide ADU laws while applying its own local development standards.

Overview & Permit Process

  • ADUs require both Planning and Building permits through the ePermits Center; ministerial review only (no discretionary review).
  • Pre‑approved (PADU) plans are available to streamline the process, but still need site‑specific review.
  • No ADUs permitted for short‑term rentals.

Unit Types & Size Limits

  • JADUs: ≤ 500 sq ft, inside single‑family homes or garages.
  • Attached ADUs: Either within existing footprint (converted attic, garage) or as additions.
  • Fire‑rated separation required.
  • Detached ADUs:
    ○ ≤ 800 sq ft and ≤ 16 ft height = streamlined, no parking required
    ○ Larger/new ones allowed with full review.
  • Under California law: detached ADUs up to 1,200 sq ft allowed; Contra Costa currently caps at ~1,000–1,200 sq ft depending on zone. On lots <10,000 sq ft, max ADU size is 640 sq ft; larger lots allow up to 1,000 sq ft.

Parking & Setbacks

  • No parking required for ADUs ≤ 800 sq ft or near transit, historic districts, or when replacing garage spaces.
  • Detached ADUs typically require 4 ft side/rear setbacks.

Fees & Impact

  • Standard building fees apply; significant impact fees (e.g. sewer, traffic, park) can sum to ~$50k unless the unit lacks a kitchen.

Legal Updates

  • The County recently amended its ADU ordinance (Ordinance 2025‑07, adopted May 13, 2025) to align with new state law—now allows more ADUs per lot, broader parking exemptions, and removes subjective standards.
  • However, in Dec 2024, California HCD found the 2023 ordinance non‑compliant on points like combinations of ADUs/JADUs, objective standards, and parking – the 2025 amendment should address these .

Planning an ADU or Home in Contra Costa County

Create space for family, plan for the future, or increase your property's flexibility with a prefab ADU, duplex, or single-family home can be a smart long-term investment. Backed by more than 40 years of California development experience, Perpetual Homes ADU helps Contra Costa County homeowners build with confidence.

Our 10-Step Process

Areas We Serve Throughout Contra Costa County

We are proud to build high-quality prefab ADUs and homes across Northern California and beyond.
Don't see your city listed? Contact us for a free virtual assessment and explore what's possible on your property.

  • Unincorporated Communities: Alamo •  Bay Point  •  Bethel Island  •  Blackhawk  •  Canyon  •  Clyde  •  Crockett  •  Discovery Bay  •  El Sobrante  •  Kensington  •  North Richmond  •  Pacheco  •  Port Costa  •  Rodeo  •  Rossmoor  •  Saranap  •  Tara Hills  •  Tassajara  •  Vine Hill

Models Available for Tours

in Contra Costa County

These models are available for an in-person visit at our Northern California locations. You can schedule an appointment with a member of the Perpetual Homes ADU team to walk through a completed ADU, explore layout options, and see the quality of our prefab and modular backyard homes at affordable prices.

The Healdsburg by Perpetual Homes ADU
The Sonoma by Perpetual Homes ADU
The Pasadena by Perpetual Homes ADU
The Claremont by Perpetual Homes ADU
The Newport by Perpetual Homes ADU
The Berkeley by Perpetual Homes ADU
The Malibue by Perpetual Homes ADU
The Communal by Perpetual Homes ADU
Place an Perpetual Homes ADU on your California property

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Why Homeowners Choose Perpetual Homes

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Experienced California ADU & Home Builder

Family-owned with 40+ years of experience, 250+ prefab homes built, and 20+ customizable floor plans across California.

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Highly Customizable Floor Plans

Choose from a variety of customizable ADUs, duplexes, and single-family homes with designer finishes, flexible layouts, and energy-efficient features.

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Full-Service Design & Permitting

From site evaluation and engineering to permitting and construction, our experienced team manages every step of your project.

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Transparent Pricing & Peace of Mind

Financing resources, a 7-year warranty, and recognized as the 2026 Prefab ADU Development Company of the Year by Construction Business Outlook.

Find the Perfect Home for Your Lifestyle

Browse our collection of prefab ADUs, duplexes, and single-family homes designed for residential properties throughout California. Compare floor plans, personalize finishes, and discover home designs that fit your property, budget, and lifestyle.

Frequently Asked Questions

  • What are Accessory Dwelling Units (ADUs)?

    ADUs are separate housing units built on existing single family residential properties. ADUs are also known as secondary dwelling units, guest houses, backyard cottages, mother-in-law units and granny flats.


    There are many different types of ADUs, including both separate structures located in back or side yard (detached) and conversions of existing spaces such as basements, attics and garages.

  • How do I know if my property is suited for a Perpetual Home?

    Many different types of properties will accommodate an ADU. In most cases, properties with a flat backyard with few obstructions, and where an open space with minimum dimensions of 45′ x 25′ can be created, will work. If you aren’t sure, contact us and we’ll review property information online and even perform a site visit to determine if your property is suitable for a Perpetual Homes.

  • What amenities does Perpetual Homes offer?

    ADUs are separate housing units built on existing single family residential properties. ADUs are also known as secondary dwelling units, guest houses, backyard cottages, mother-in-law units and granny flats.


    There are many different types of ADUs, including both separate structures located in back or side yard (detached) and conversions of existing spaces such as basements, attics and garages.

  • What is the cost of a Perpetual Homes to a homeowner?

    Perpetual Homes sells fully installed ADUs in the California market starting in the mid price of $100,000’s. This price includes all permits, installation costs, utility connections, appliances, and landscaping. Perpetual Homes is one of the most affordable but high-quality options for a detached ADU.


    Because of the variability of site characteristics, Perpetual Homes' fixed price will not cover the cost of removing existing structures, large trees, underground storage tanks, cesspools, and other impediments to installing an ADU, nor will Perpetual Homes cover the cost of non-standard installations or utility connections, or upgrading utility service to a property to serve the ADU. In addition, impact fees can vary, these costs are passed through to the homeowner.

Ready to Get Started?

Have questions about building a prefab home in Contra Costa County? Schedule a free consultation with the Perpetual Homes ADU team to discuss your property and explore your options.

Disclaimer: The information on this page is provided for general informational purposes only and is not legal, zoning, or permitting advice. Requirements vary by jurisdiction and may change over time. Always verify current regulations with your local Planning Department before beginning your project.