Areas we serve

Napa County

Build a Custom Prefab ADU or Home in Napa 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 & Permitting Guide for Napa County

Unit Types & Quantity

  • Allows one ADU (attached, detached, or conversion) and one JADU on lots with single‑family or multifamily dwellings; also follows state allowances for multifamily lots

Size, Setbacks & Height

  • State baseline: up to 1,200 sq ft, 16 ft height, 4 ft side/rear setbacks
  • Attached ADUs capped at 50% of the primary home’s size; JADUs ≤ 500 sq ft

Parking & Fees

  • One parking space required per ADU except if ≤ 800 sq ft, conversions/JADUs, near transit, in historic districts, part of an existing structure, etc.
  • Impact and building fees apply proportionally; units under 750 sq ft may waive fees.
  • County runs an Affordable ADU Forgivable Loan program (up to $10,000 for fees, plus funds for plans and escrow)

Permitting Process

  • Ministerial building permits; pre-approved plan options supported via Napa Sonoma ADU and county websites

Compliance Review

  • The County adopted Ordinance No. 1495 in Sept 2024, but the state HCD issued a non‑compliance letter in Feb 2025 regarding multifamily ADU counts, deed restriction limits, and parking exemptions. They must respond by March 20, 2025

Official Resources

Planning an ADU or Home in Napa 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 Marin County homeowners build with confidence.

Our 10-Step Process

Areas We Serve Throughout Napa 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: Angwin  •  Deer Park  •  Oakville  •  Pope Valley  •  Rutherford  •  Spanish Flat
Place a Perpetual Homes ADU on Your Lot - Enter your address to see which of our models fit your California property.

Place an ADU on Your Lot

Enter your address to see which of our customizable and affordable

prefab ADU models fit your California property. You can drag, rotate, and compare backyard homes to confirm the right size and placement before starting your project.

See What Fits on Your Property

Why Homeowners Choose Perpetual Homes ADU

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Experienced California ADU & Home Builder

One of California's largest family-owned prefab ADU and home builders, helping homeowners navigate the building process with confidence.

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Highly Customizable Floor Plans

Choose from ADUs, duplexes, and single-family homes with flexible floor plans, designer finishes, 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 Napa 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.