A crane lowers the second half of an accessory dwelling unit, or ADU, to its foundation in Topsham in late May. The unit was built by Brunswick-based Backyard ADUs. ADUs are homes that are slightly larger than so-called tiny houses. They are becoming increasingly popular as Maine’s existing housing crunch worsens. Ben McCanna/Staff Photographer

Kate Blackmer’s stop in Tenants Harbor last year was intended to be a weeklong visit with her parents, just a short stopover in her move from Michigan to her longtime family home in Nova Scotia.

But then the Canadian border closed, and Blackmer, who does not have Canadian citizenship, was forced to stay put.

Now, over 15 months later, Blackmer, “marooned by COVID,” is still in Tenants Harbor, waiting for the border to reopen. But she’s not in a rush to leave.

In January, Blackmer, who nixed the idea of buying a house in today’s competitive real estate market, moved into a roughly 700-square-foot accessory dwelling unit, or ADU, about 300 feet from her parents’ farmhouse.

Her “dream home,” she was able to design everything “to an inch of what exactly I wanted.” It’s more than enough room for her, and with her own kitchen, bathroom and two bedrooms, it offers all the privacy and independence of her own home, with a smaller footprint and a stone’s throw from her parents.

Freshly moved from a trailer, an accessory dwellings unit, or ADU, built by Brunswick-based Backyard ADUs rests on its foundation in Topsham. ADUs are homes that are slightly larger than so-called tiny houses. They are becoming increasingly popular as Maine’s existing housing crunch worsens. Ben McCanna/Staff Photographer

Real estate experts expect many more Mainers will build ADUs – sometimes called granny flats or in-law suites – as the state’s housing crunch and pandemic-related moving trends continue. And the Maine Legislature this session approved a bill that could make it easier for people to build them.


Bigger than a typical “tiny home,” an ADU is a small residence – usually 600 to 1,000 square feet – that shares a single-family lot with a larger, primary dwelling. ADUs are independent living spaces with their own kitchens, bathrooms and sleeping areas. They can be detached in the backyard, above the garage or built onto the home like an addition, depending on local regulations. Tiny houses can be considered ADUs, but ADUs are not exclusively tiny houses.

ADUs, which are gaining traction in Maine, can be an attractive option for families who want to keep relatives close by, families seeking a supplemental source of income, renters or would-be-homeowners in search of more affordable housing options, and municipalities that need more housing stock and increased density but lack the space to put it.

However, high costs, outdated and inconsistent local building codes, and “not in my backyard” attitudes could down what could be the state’s next housing boom.


Construction wrapped on Greg Norton’s South Portland ADU in March 2020, just days before the state went into lockdown. 

He and his wife, Kelly, purchased her childhood home from her parents, Tim and Karen Coyne, and built an addition (South Portland does not allow detached ADUs) for them to move into.


It was a way to make room for their growing family and keep the house, which had been in the family since Karen Coyne was a child, for a third generation, while also keeping the Coynes close by to help out with their grandchildren, Mary, 7 and Riley, 5. During the pandemic, with school closures and remote work, this proved even more helpful than anticipated, Norton said.

Tim and Karen Coyne in the kitchen and living area of their accessory dwellings unit, or ADU, in South Portland on June 18. Brianna Soukup/Staff Photographer

“Keeping it in the family, that’s part of the literal and figurative value of this,” he said.

While building an ADU wasn’t inexpensive – Norton said it worked out to about $250 per square foot – buying the home from the Coynes allowed the family to stay in the area. 

“In South Portland, it’s just booming right now. Otherwise, we could not have dreamed of getting a house in this area at this price,” he said. “It’s so easy to see around here that people come in and flip houses and sell them at a monstrous profit. … I found that this is an interesting way, if you’re willing to live near an in-law like this, to stay put and take advantage of the situation. It’s really the best of both worlds.” 

Norton’s background in architecture also helped keep the costs lower than they might have been, as he was able to design the addition. The two-story, 800-square-foot addition is attached to the main house by a breezeway. It’s “not flashy,” Norton said, more of a “green monopoly house style,” but it matches with the rest of the home, which is required under South Portland’s ordinance to help keep the integrity of the neighborhood.

More people are living in multi-generational households now than they have in decades.


In 2016 a record 64 million people, or 20 percent of the U.S. population, lived with multiple generations under one roof, according to a Pew Research Center analysis of census data. This is the highest share of the population living in this type of household – defined as including two or more adult generations, or including grandparents and grandchildren younger than 25 – since it declined from 21 percent in 1950 to a low of 12 percent in 1980. Roughly 28.4 million Americans lived in households with three or more generations.

Chris Lee has been planning and building prefabricated ADUs in Maine and Massachusetts with his Brunswick company, Backyard ADUs. The houses range from 450 to 1,350 square feet, but the “sweet spot,” he said, 600 to 800 square feet.

More and more people are pursuing multi-generational living, he said, but instead of cramming into the same house, they’re doing it ADU-style, where everyone can have their own space and privacy.

Greg and Kelly Norton, far left and far right, inside the accessory dwelling unit, or ADU, at their home in South Portland on Friday. The couple bought the home from Kelly’s parents, Karen and Tim Coyne, center, and built the unit so they could stay on the property with them. Brianna Soukup/Staff Photographer

In many cases, older parents will downsize and, instead of finding a retirement community, move into their kids’ backyards to be close to family and help out with grandchildren. Alternatively, Lee said, more young people are moving back home – but instead of the quintessential move to the parents’ basement, they’re able to set up shop in their own small home.

It’s unclear how the changes brought on by the pandemic may impact these numbers in the long term, but Nancy Smith, director of GrowSmart Maine, an organization that advocates for sustainable development, said it makes sense that there’s been an uptick in interest in ADUs in the past year.

“More families are co-housing. Kids are coming home to work remotely,” she said. “We’re seeing changes in where people want to live. People who are in the homes where they’ve raised their children, and their kids are all gone now, have the choice of selling and moving elsewhere, or (considering) how can they adapt it and stay there in a way that makes sense?”


Moving back home was never part Blackmer’s plan – at 51, she hasn’t lived with her parents since she was 15 – but there’s comfort in knowing there’s a place for her or her brother to stay so close to her 76-year-old parents should they ever need help.

The ADU, which she designed with the help of her cousin, Parlin Meyer, director of BrightBuilt Home in Portland, took only a matter of weeks to construct once the planning was done and the foundation was dug. Blackmer declined to say how much the ADU cost, but Meyer said Brightbuilt’s “Sidekick” option can run from $100,000 to $250,000.

A worker guides an accessory dwelling unit, or ADU, onto its foundation in Topsham on Thursday. Ben McCanna/Staff Photographer

When she returns to Canada full time, Blackmer believes the property also presents an opportunity for her parents, Elizabeth and Hugh Blackmer, to recoup some of what they spent on it.

“If I wasn’t here it could be rented out easily, like in an afternoon,” she said. “It’s a gorgeous thing.”


ADUs can also increase density and boost critically needed housing stock in a community without creating additional lots or infrastructure.


“There’s efficiency for municipal services,” Smith said. “Whether you’re within the home or near it, you have the advantage of … the same utility lines, same roads same trash pickup.”

Paul Peck, a real estate developer, attorney and board member on the Maine Real Estate and Development Association, a nonprofit that promotes responsible development and real estate ownership, said that in today’s expensive climate, smaller houses may be the only way to bump up housing density, though the current cost of materials may give some potential buyers sticker shock.

An ADU can run anywhere from $100 to $400 per square foot, and while there are fewer square feet than in a typical small house, it also means that more amenities are packed into a smaller space, essentially driving up the cost per square foot.

Lee estimated that costs for ADUs have risen roughly 25 percent in the past year because of the rising prices of materials and labor.

Meyer, the director of BrightBuilt Homes, said cost remains the top barrier for homeowners.

“You’re still building another structure that includes some of the higher-ticket items like a kitchen or a bathroom,” she said. “An ADU is going to be more than what most people have just on hand.”


From back left, Tim Coyne, Karen Coyne, Kelly Norton, Greg Norton and their daughters, Riley, 5, front center, and Mary, 7, outside of their accessory dwelling unit, or ADU, (on right) at their home in South Portland on Friday. Brianna Soukup/Staff Photographer

That said, two things work in the homeowner’s favor: With a hot housing market, people have greater value in their homes and may be able to get bigger home equity loans. And interest rates are at historic lows.

“That and some of the towns are adopting ADU protocols, so many towns are getting far more progressive about policies,” Meyer said.

Portland is a prime example of a city that recently took a second look at its ADU policies.

As part of the city’s rewrite of the land use codes, officials removed some “cumbersome” zoning and procedural requirements and instituted a blanket allowance for up to two ADUs on any property in residential use, said planning director Christine Grimando.

Under the new ordinance, the property owners must occupy at least one of the residences, and the ADUs are limited to two-thirds the size of the main house. On Peaks Island, neither the accessory unit nor the principal may be used for short-term rentals. In the city, ADUs will fall under the same short-term rental restrictions as any other property. Currently, such rentals are capped at 400.

“In planning and zoning there are a certain number of dwelling units allowed in one place, but the ADU lets you leapfrog over that,” said Nell Donaldson, director of special projects. “It lets you increase density in a way that’s meant to feel gradual and incremental rather than a 30-unit apartment building.”


The ordinance is too new to say how much of an impact it will have, but Grimando and Donaldson said they anticipate an uptick. They said they’ve noticed an increase already, but the city has never had a way to flag an ADU-specific building permit, so there’s no way to know how many were in the city before.


When BrightBuilt launched its Sidekick and Sidekick Mini models, it was in response to a desire to use them as short-term rentals.

Maine has the highest percentage of vacation homes in the country. Short-term rental restrictions have been hotly debated across the state – they are a moneymaker for homeowners and a boon for the state’s tourism economy, but advocates for greater regulation contend that short-term rentals take business away from hotels and B&Bs, drive up housing costs and create a nuisance for residents of quiet neighborhoods.

Kelly and Greg Norton inside the accessory dwelling unit, or ADU, they built at their home in South Portland on Friday. Brianna Soukup/Staff Photographer

“There’s concern about the character of the neighborhood,” said Smith, the GrowSmart Maine director. “What we’ve seen is if someone is proposing one where there hasn’t been one before, people are resistant to change.”

One of the primary ways around this, she said, is for local zoning ordinances to ensure that the owner of the property is living in one of the units to help maintain a sense of neighborhood.


State lawmakers are also moving in favor of ADUs. The Legislature this session passed a bill, L.D. 1312, that requires all municipalities to allow at least one accessory dwelling unit on the same lot as a single-family house and to establish design standards for them. The bill awaits a decision on funding. The measure carries an estimated $95,000 price tag to reimburse municipalities for 90 percent of the costs associated with permitting activities. The cost, according to the fiscal note, assumes that code enforcement officers will have to work additional time to issue compliance with all regulations. Once funded, the bill will go to Gov. Janet Mills for her signature.

Some municipalities argue that the bill is an infringement on their right to set zoning codes.

GrowSmart Maine, though, says ADUs strengthen neighborhoods by adding housing options.

“ADUs can provide a home for young people starting out in a community, or for single adults not looking to own, to elders who want to stay in their homes but may need live-in assistance or extra income,” board member Lynne Seeley said in her testimony supporting the bill.

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