With housing costs on the rise, many people are searching for cost-effective ways to add more livable space to their property. Whether you need to accommodate a family member, generate rental income, or increase property value, an Accessory Dwelling Unit (ADU) is a popular option for many homeowners.

At the same time, manufactured homes are becoming a highly sought-after way to build living spaces quickly and at a more affordable price point than stick-built construction. This poses an important question: can a manufactured home qualify as an ADU?

In Oregon, the answer is often yes, but the details matter. Each local jurisdiction has its own zoning rules, construction standards, and placement requirements, which all play a role in whether you can use a manufactured home as an ADU.

In this guide, we explain everything you need to know about manufactured home ADU regulations in Oregon. Read on to take a closer look.

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What Is an Accessory Dwelling Unit (ADU)?

A yellow manufactured home with a lime green door installed in the backyard, behind the main home, functioning as a cute and comfortable accessory dwelling unit (ADU) on the owner's property.

An accessory dwelling unit (ADU) is a secondary living space located on the same lot as a primary home. ADUs are commonly used as on-site housing for family members, caregivers, or tenants, and are regulated as permanent dwellings. They can either be attached to the main home, built as an interior modification, or detached.

Before being approved for occupancy, an ADU must meet all local building codes and safety regulations, which vary between different states, counties, and cities.

All ADUs must include:

  • Kitchen
  • Bathroom
  • Sleeping area
  • Independent exterior entrance

Since a manufactured home can be attached to a permanent foundation and connected to utilities, it can function as a long-term residential structure and often counts as an ADU.

However, the exact requirements for qualification may depend on local and state regulations.

ADU Regulations in Oregon

A grey manufactured home installed in the backyard of the main home, functioning as a cute and comfortable accessory dwelling unit (ADU) on the owner's property.

Local jurisdictions (your city or county) are typically responsible for implementing and enforcing ADU regulations. They can adopt zoning codes, development standards, and permitting processes for ADUs, but must ultimately comply with state laws.

Below is an overview of ADU regulations in Oregon1, according to the Department of Land Conservation and Development:

  • Allowance: Cities with populations over 2,500 and counties over 15,000 must allow ADUs within urban growth boundaries in zones that allow detached single-family dwellings.
  • Attachment: An ADU can be interior, attached, or detached, and is accessory to a single-family dwelling.
  • Permitting: Local jurisdictions are responsible for reviewing applications, issuing permits, and enforcing compliance.
  • Local standards: Local governments can set reasonable siting and design standards as long as they are clear, objective, and do not conflict with state law.

In many cases, a manufactured home can qualify as an ADU in Oregon, as long as they meet local and state requirements. Understanding this regulatory framework can help prevent delays in your project and ensure the manufactured home you choose aligns with local ADU regulations.

Manufactured Home ADU Regulations in Oregon

The exterior of the Cascadia Value 12351L manufactured home, a popular ADU option

Many Oregon counties allow a manufactured home to be an ADU2 as long as it:

  • Meets local ADU standards
  • Is ENERGY STAR certified
  • Has proper HUD certification

These requirements focus on how the home is built, certified, installed, and connected to the property.

Below are the key regulatory areas that typically apply when using a manufactured home as an ADU:

Zoning and Lot Eligibility

Before a manufactured home can be approved as an ADU, the lot itself must be eligible. Local zoning laws determine which properties can have an ADU and whether it can be its own detached structure.

Zoning laws also regulate where the structure can be placed on the lot as well as access requirements. If a manufactured home is used as an ADU, it must meet the same zoning standards as other detached units, unless a local ordinance states otherwise.

HUD Code Compliance

Any manufactured home must meet HUD standards, regardless of whether it’s being used as an ADU. These strict codes regulate construction quality, structural integrity, fire safety, and energy efficiency. They are also essential for confirming that the home is built for permanent residential use.

When it comes to permitting, a manufactured home must have an HUD certification label to legally qualify as an ADU. This is a permanent metal plate signaling the home meets all necessary building codes and safety standards.

ENERGY STAR Certification Requirements

Some Oregon jurisdictions require a manufactured home to be ENERGY STAR certified to qualify as an ADU.2 This program is run by the U.S. Department of Energy (DOE) to help consumers save money on energy costs while reducing waste.

ENERGY STAR certification ensures homes meet strict standards for insulation, windows, duct sealing, HVAC, and appliances. It involves thorough third-party inspections to ensure everything is compliant from start to finish.

For manufactured homes, these standards can result in significantly lower utility bills, improved comfort, better indoor air quality, and fewer greenhouse gas emissions. They also help make the building eligible as an ADU, although this varies from county to county.

Always check with your local government to verify which regulations are required for a manufactured home to serve as an ADU.

Foundation and Installation Standards

An ADU must be a permanent dwelling installed on a foundation that meets local and state building codes. For manufactured homes, HUD has specific installation standards to follow:

  • Foundations: Homes must be installed on a foundation that supports the home’s weight and resists movement.
  • Anchoring: Homes must be secured with tie-downs to resist wind forces.
  • Skirting: Open spaces under the home must be enclosed with skirting to protect the undercarriage from pests and moisture damage.
  • Utilities: Water, gas, and electrical connections must be properly installed and accessible for maintenance.
  • Inspection: After installation, the home must be inspected by an HUD-approved authority to receive formal certification.

These standards ensure the manufactured home functions as a permanent structure and can potentially qualify as an ADU.

Size, Height, and Setback Compliance

Most Oregon jurisdictions have specific requirements governing ADU size, height, and setback:

  • In Oregon, a detached ADU cannot exceed 800-900 square feet of floor area, or 75-85% of the primary home’s floor area—whichever option is smaller.1
  • The maximum height limit tends to range between 20-25 feet, although this varies depending on the jurisdiction.3,4
  • Setback refers to the minimum distance structures must be from property lines. This ensures open space for safety, access, privacy, and utility maintenance.

While size requirements are typically mandated by state laws, height and setback requirements generally vary from place to place. Always check with your local government to learn what regulations apply in your area. 

Start Planning Your Manufactured Home ADU Build Today

An accessory dwelling unit (ADU) is a secondary living space designed to accommodate family members, tenants, or caregivers. Manufactured homes can qualify as an ADU in Oregon, as long as they meet HUD codes and local building regulations. Understanding these rules upfront will help you choose the right floor plan and prevent permitting delays from stalling your project.

As a full-service manufactured home retailer and general contractor, Len’s Home Center is your one stop shop for building an affordable ADU on your property. We’ll walk you through the entire process from start to finish, handling everything from selecting compliant floor plans and securing permits to building the final touches that make an ADU feel like a home.

Ready to take the next step? Browse our portfolio for inspiration and contact our manufactured home experts online today.

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  1. Klepinger, M. & Oregon Department of Land Conservation and Development. (2018). Guidance on Implementing the Accessory Dwelling Units (ADU) Requirement Under Oregon Senate Bill 1051. In ADU Guidance (September 2019) [Report]. https://www.oregon.gov/lcd/Publications/ADU_Guidance_updatedSept2019.pdf 
  2. Marion County Planning Division. (2017). Accessory Dwelling Units Regulations for accessory dwelling units in Marion County. In Marion County. https://www.co.marion.or.us/PW/Planning/Documents/ADU.pdf 
  3. Create an Accessory Dwelling Unit on Your Property. (n.d.). City of Salem. https://www.cityofsalem.net/business/land-use-zoning/development-application-help/create-an-accessory-dwelling-unit-on-your-property 
  4. Accessory dwelling unit (ADU) zoning requirements. (n.d.). Portland.gov. https://www.portland.gov/ppd/zoning-land-use/zoning-code-overview/adu-zoning