Accessory Dwelling Units, often called ADUs, are quickly becoming one of the most talked-about housing trends in Maine. Thanks to recent changes in state law, building an ADU is now more accessible than ever for homeowners. Whether your goal is rental income, multigenerational living, or increasing your home’s resale value, understanding Maine’s ADU regulations can unlock major opportunities.

If you’ve ever thought “What could I do with that garage, basement, or extra space?”, an ADU might be your answer.

What Is an Accessory Dwelling Unit (ADU)?

An Accessory Dwelling Unit is a smaller, independent living space located on the same property as a primary residence. It must have:

  • A kitchen

  • A bathroom

  • Sleeping and living space

  • Its own entrance

In Maine, ADUs can be:

  • Inside your existing home (basement or attic apartment)

  • Attached (like an in-law suite)

  • Detached (a backyard cottage or apartment over a garage)

Maine’s New ADU Laws: What Changed?

Maine updated its housing laws to encourage more housing options statewide. These changes reduce red tape and require municipalities to allow ADUs in most residential zones.

Here are the highlights every homeowner should know:

1. ADUs Are Allowed “By Right”

Towns must allow at least one ADU per single-family lot in residential areas. This means most homeowners cannot be denied simply because their town doesn’t “like” ADUs.

2. Flexible Design Options

You can build your ADU:

  • Inside your home

  • Attached to your home

  • As a detached structure

This gives homeowners flexibility to choose the option that best fits their property and budget.

3. Parking Requirements Are Limited

Municipalities cannot require extra parking specifically because of an ADU. This removes one of the biggest historical barriers to approval.

4. ADUs on Non-Conforming Lots

Even if your property doesn’t meet modern zoning standards, you can still add an ADU as long as it doesn’t worsen the nonconformity. That’s huge for older neighborhoods in Maine.

5. Minimum Size Requirement

An ADU must be at least 190 square feet, though each town may set a maximum size.

6. Shoreland Zoning Still Applies

If your property is near lakes, rivers, or the coast, shoreland zoning rules still apply. However, towns cannot automatically ban ADUs in these areas if environmental standards are met.

Why ADUs Are a Smart Move for Maine Homeowners

1. Create Rental Income

An ADU can generate:

  • Long-term rental income

  • Seasonal rental income (depending on local rules)

  • Financial stability in uncertain markets

This is especially attractive in high-demand areas like Portland, South Portland, Scarborough, Cape Elizabeth, Brunswick, and other coastal towns.

2. Increase Property Value

Homes with flexible living space are in high demand. An ADU can:

  • Increase marketability

  • Improve resale value

  • Attract investors and multigenerational buyers

Buyers love options, and ADUs offer built-in versatility.

3. Support Multigenerational Living

ADUs are ideal for:

  • Aging parents

  • Adult children returning home

  • Family members who want independence with proximity

This allows families to stay close without sacrificing privacy.

4. Future-Proof Your Property

Housing trends are shifting toward flexibility. An ADU turns your home into a multi-purpose investment that can adapt to future needs.

How to Get Started with an ADU in Maine

  1. Check Local Zoning Ordinances
    Every town has its own specific requirements beyond state minimums.

  2. Consult Your Local Code Enforcement Officer
    They can confirm:

    • Setbacks

    • Septic requirements

    • Utility connections

    • Permit needs

  3. Budget Carefully
    ADU costs vary depending on:

    • Size

    • Whether it’s attached or detached

    • Utility access

    • Design quality

  4. Think About Your Long-Term Plan
    Will this be:

    • A rental unit?

    • Housing for family?

    • A resale feature?

Design decisions should support your long-term goals.

Final Thoughts: ADUs Are a Major Opportunity in Maine Real Estate

Maine’s updated ADU laws represent a shift toward smarter, more flexible housing. For homeowners, this means:

  • More income potential

  • More housing options for family

  • Increased property value

  • Stronger resale appeal

Accessory Dwelling Units aren’t just a trend—they’re becoming a powerful real estate strategy. If you own property in Maine, an ADU could be one of the best investments you make in your home’s future.