Room for Mom. Room for the kids. Right on your lot.
Maine law now lets almost every homeowner add a second, smaller living space – called an accessory dwelling unit (ADU) – a garage apartment, an in-law suite or a backyard cottage. Kota handles it from the first septic question to the final certificate of occupancy.
Maine ADUs on the Rise
516
ADUs permitted across Maine in 2025, 7% of all new homes. The state says the real number is likely higher.
Maine Office of Community Affairs, 2025 Statewide Housing Data, June 2026
1 in 4
Older homeowners say they’d consider building an ADU.
AARP Home & Community Preferences Survey, 2024
44.8
Maine’s median age, the oldest of any state.
Maine State Economist, July 2025
Four ways to add an ADU
The most affordable ADU is usually the one that modifies a structure you already have.
Interior conversion
Starting at $40,000. A basement, attic or wing of the house becomes its own apartment with a private entrance.
Garage or barn conversion
Starting at 75,000. Classic New England: the carriage house or garage apartment, with living space above or in place of the bays.
Attached addition
Starting at 150,000. An in-law suite with its own door, sharing a wall and often utilities with the main house.
Detached cottage
Starting at 200,000. A separate small home in the yard. It gives both households the most privacy and needs the most site work.
Every lot is different. Septic upgrades, well capacity, electrical service and ledge can move these numbers. We price them out before you commit.
Thinking about an ADU?
Start with a free lot check. We’ll tell you what fits and what it’ll take.
How Kota makes ADUs happen
5 steps to your new space
- Lot check. We walk the property and check zoning, setbacks, septic and well capacity, and shoreland rules before you spend a dollar on design.
- Design for how you’ll live. Single-floor living, wide doors and a heat pump, sized to your budget and to who’ll live there in 10 years.
- Permits, handled. We prepare the drawings and coordinate the septic designer and code office.
- Build. Foundations below frost, a tight envelope and a Kota crew on site. We keep the job clean because your family lives next door.
- Move-in. Final inspections, the certificate of occupancy and a walkthrough.
Maine law is on your side
Current and future legislation is enabling more ADU development throughout the state.
At least one ADU per lot
Allowed on a lot with a single-family house, anywhere homes are allowed.
Inside, attached, or detached
Finish the basement, convert the garage, build an addition or put up a cottage in the side yard.
No extra parking
Towns can’t require more parking for an ADU than the main house already needs.
Lake lots aren’t off-limits
Towns can’t ban ADUs outright in the shoreland zone, though state shoreland rules still apply.
Old apartments can go legal
An in-law unit built without a permit must be allowed if it otherwise meets the rules.
No sprinklers for 1–2 units
Since September 2025, a town can’t require fire sprinklers for an ADU at a single-family home.
Coming by July 1, 2027
No owner-occupancy rule
Towns won’t be able to require the owner to live on the lot. Some towns, including Windham and Gorham, still do today.
No planning board
ADUs can’t be sent to the planning board. A building permit and site review will do.
More kinds of lots
ADUs will also be allowed with two- and three-unit homes, and most lots can hold three homes, counting the ADU.
Your town still sets size limits, setbacks and fees, and your septic system has to handle the extra bedrooms. Sources: 30-A M.R.S. §4364-B; P.L. 2025 c.385 and c.733; Maine Office of Community Affairs guidance, 2026. General information, not legal advice.
Mainers are already doing this
“It’s priceless.”
Susan, Falmouth, who moved into an 840 sq ft in-law addition next to her daughter’s family
“Our daughter is 25 feet away from us, but we’re feeling like we’ve got an empty house.”
Richard, Cape Elizabeth, whose adult daughter lives in a 750 sq ft cottage in the side yard
“When this possibility came along, I jumped at it.”
Janice, 80, Yarmouth, who legalized her studio and rents it out to stay in her home
As reported in the Portland Press Herald, May 6, 2026.
Built for Maine, not California
Most ADU advice online comes from warmer places with city sewer. Here, an ADU has to handle frost, septic and a long heating season.
Septic comes first
Maine’s wastewater rules size systems by bedroom. We bring in a licensed site evaluator early, so a septic upgrade doesn’t surprise you halfway through.
Frost-proof foundations
Footings go below local frost depth, or we use a frost-protected shallow foundation where code allows.
Heat pumps & tight envelopes
A small, well-sealed unit heats cheaply with a heat pump. We’ll point you to current Efficiency Maine rebates.
Lakes & shoreland
Around Sebago, Long Lake and the Presumpscot, state shoreland setbacks and expansion limits apply. We plan around them from day one.
ADU questions we hear every week
Can I rent out my ADU?
Usually, yes. Some towns, including Windham and Gorham, still require the owner to live on the property; state law removes that rule by July 1, 2027. Standish, Freeport and Yarmouth already don’t require it. Many towns limit short-term rentals: Saco bans rentals under a month, and Naples under 60 days. We’ll check your town’s rules.
How big can an ADU be?
Each town sets its own cap. Windham and Gorham allow 800 sq ft, Standish 1,000, and Raymond up to 1,250 (smaller than the house). The state minimum is under 200 sq ft, so a tiny studio counts too.
How long does it take?
For a conversion, figure a few months from permit to move-in. A detached cottage takes longer, especially if the septic needs work. Design and permitting over the winter lets you break ground in spring.
How do people pay for an ADU?
Common options are savings, home equity loans, and construction loans from Maine banks that count part of the future rent toward qualifying. Fannie Mae and Freddie Mac now let expected ADU rent count toward mortgage qualifying, up to 30% of income.
I already have an in-law apartment that was never permitted. Now what?
Under the current law, a town must allow an ADU built without approval if it otherwise meets the requirements. We can help bring it up to code and make it legal.
Get your ADU lot check started today!
Tell us your town and who the ADU is for, and we’ll be in touch.