What States Allow ADUs: The Top 3 Current ADU-Friendly States

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With affordability being one of the most significant factors for buyers, accessory dwelling units (ADUs) have made a splash in the housing market. ADUs, also known as mother-in-law units, granny flats, or backyard cottages, are secondary housing units, either attached or detached from the primary residence within a property. ADU housing concepts have been around for some time and have been utilized for various purposes, including housing family members, home offices, or, for investors, generating additional rental income. 

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What is an ADU?

Before jumping into the legal landscape and what states allow ADUs, it’s important to understand what qualifies as an ADU. As a stand-alone additional living quarter within the same lot as an existing single-family home, an ADU space requires permanent living, sleeping, eating, cooking, and sanitation facilities within a separate, contained living space. 

These self-sufficient tenant dwellings within a residential property come in a variety of forms, including:

  • Detached structures 
  • Converted garages
  • Basement apartments
  • Tiny homes

While ADU housing gives homeowners the chance to take in family members, for investors, ADU concepts create opportunities for: 

  • Increased rental income
  • Expanded and full property use   
  • Increased property value
  • Tenant diversity
  • Enhanced living flexibility

For long-term residential real estate investors, the question isn’t whether you should add an ADU to your investment property, but rather, can you?

How Much Does it Cost to Add an ADU?

Now that you know what states allow ADUs and some of the varying regulations surrounding them, you’re probably wondering how much an ADU addition will cost. Like their regulations, ADU plans and costs can vary significantly. Average estimates range from $60,000 to $285,000. With building costs between $150 to $300 per square foot of an ADU addition, it’s important to ensure you have the right plan and adequate financing to succeed. 

FACo’s team of residential real estate experts can help you navigate the complexities of ADU housing regulations while providing the most reliable and comprehensive financing programs. 

If you’re looking to add an ADU unit to a single-family property, speak to a member of our knowledgeable staff about financing options. CLICK HERE to schedule a FREE consultation with a FACo team member today. 

Frequently Asked Questions

1. What is an accessory dwelling unit (ADU) in real estate?

An accessory dwelling unit (ADU) is a secondary residential unit located on the same property as a primary home. ADUs can include detached backyard cottages, converted garages, basement apartments, or attached living quarters. To qualify as an independent dwelling, an ADU generally needs permanent facilities for sleeping, cooking, and sanitation. Real estate investors may use eligible ADUs to generate additional rental income.

2. What states allow accessory dwelling units (ADUs)?

Many U.S. states allow accessory dwelling units under certain conditions, including California, Colorado, Oregon, Washington, Maine, Arizona, Florida, and Massachusetts. However, ADU regulations vary significantly by state, city, and property type. Some jurisdictions encourage ADU construction, while others impose zoning, size, or occupancy restrictions. Investors should verify current local requirements before purchasing property or beginning an ADU project.

3. Which states are the most ADU-friendly for real estate investors?

California, Colorado, and Maine are among the states that have adopted policies intended to make accessory dwelling unit construction more accessible. These states have introduced measures addressing zoning, permitting, parking requirements, or occupancy restrictions. However, the most favorable location for an ADU investment depends on local regulations, construction costs, rental demand, and the property's potential return on investment.

4. What are the ADU regulations in California?

California has established statewide laws designed to facilitate accessory dwelling unit development on qualifying residential properties. These laws address issues such as permitting, parking requirements, unit size, and local approval procedures. However, the specific rules that apply depend on the proposed ADU and property characteristics. Investors should review current California requirements and consult the local planning department before starting construction.

5. Can homeowners associations (HOAs) restrict ADU construction?

Homeowners association restrictions on accessory dwelling units depend on applicable state laws and the community's governing documents. Some states limit an HOA's ability to prohibit otherwise permitted ADUs, while certain design and architectural requirements may still apply. Investors should review HOA covenants, local zoning ordinances, and state legislation to determine whether an ADU can legally be constructed and rented.

6. How much does it cost to build an accessory dwelling unit?

ADU construction costs vary according to location, square footage, design, materials, and site conditions. Project estimates can range from approximately $60,000 to $285,000 or more, with detached construction and extensive utility connections potentially increasing expenses. Investors should also budget for architectural plans, permits, inspections, and contingency costs. Obtaining local contractor estimates is essential for evaluating an ADU project's financial feasibility.

7. Can you rent out an ADU for additional investment income?

Yes, many jurisdictions allow property owners to rent accessory dwelling units to generate supplemental income. However, rental eligibility depends on local zoning requirements, occupancy rules, licensing obligations, and any applicable short-term rental restrictions. Investors should research local rental demand and estimate operating expenses before proceeding. A legally permitted ADU may improve a property's income potential, although profitability is not guaranteed.

8. Can real estate investors get financing to build an ADU?

Yes, qualifying real estate investors may be able to finance eligible accessory dwelling unit construction or renovation projects through specialized investment property loan programs. Depending on the project, financing options may include rehabilitation or construction loans. Finance of America Commercial (FACo) offers investor-focused financing solutions that may support qualifying residential improvement and development projects, subject to property eligibility, underwriting requirements, and loan program guidelines.

Authored by Bianca Montalvo

SEO copywriter and strategist

This content is for informational purposes only and should not be construed as investment or legal advice. Neither the author of this content nor Roc360 assumes any liability for actions taken or not taken based on information contained herein. Investments involve risk, including potential loss of principal. You should consult a qualified professional before making financial decisions.

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