One weekend in 2021, Gemma Warren was doing what she did every weekend: sitting over coffee in her home in Tulum, Mexico, combing through the real estate listings for cabins in the Catskill Mountains of New York.

She and her husband, Nick Warren, who are English, had discovered the Catskills several years earlier, while living in Brooklyn and working for public relations and marketing companies headquartered in London. They fell for the region’s scented forests, sunny meadows, icy streams and not terribly threatening bears (unless provoked). They wanted to buy a weekend house, but found nothing to fit their budget.

So six years ago, they picked up and moved to Tulum, on the Yucatán Peninsula, because they also had a sunny, oceanic side to their natures. There, they worked remotely. But the Catskills still beckoned.

In that fateful website-browsing session three years ago, Ms. Warren, now 37, saw a listing for a cabin in the western Catskills hamlet of Delancey, N.Y. The asking price: $65,000. The house was 192 square feet and lacked heating and a toilet.

“A shack” is how Mr. Warren, 38, described it: “There was running water. But that was pretty much it.”

And yet it sat on 6.8 acres thick with old trees and tall grasses. Flowing next to it was a creek that audibly burbled in a video. A large picture window looked out to the water and forest.

Investigating further, the Warrens discovered that the tiny building with its projecting shed roof had an unusual provenance. It was one of the few extant examples of a Bolt-Together House, a bare-bones cutie that Family Circle magazine published in 1972 in a series on D.I.Y. dwellings.

A young architect named Jeffrey Milstein had designed the house on paper as something that could be taken apart and moved if one didn’t happen to own the land it occupied. The building was conceived as rough-sawed plywood panels bolted to a collapsible framework of timber posts and trusses attached to four concrete piers embedded in the earth.

Family Circle, riding the wave of eco-consciousness that washed through the 1970s, handed Mr. Milstein the money to construct the house, gave it a big spread and sold the plans.

“If you have a large garage, your husband can prefabricate the panels (none is larger than 4’x8’); cut, drill and paint the posts and trusses; then move the entire house to your site in a 16-foot rented truck,” the magazine suggested to the readers it took for granted were female and married.

The cost of construction was about $2,500 ($18,680 in today’s dollars), inclusive of lumber, wiring, plumbing, heating (with a wood-burning stove), kitchen appliances and some built-in furnishings, including a fold-down dining table. There was also a platform bed on a mezzanine level reached by a wall ladder.

The house was a hit; Family Circle sold a reported 25,000 plans, more than for any other project in its series. The Italian shelter magazine Abitare featured it in the May 1979 issue along with another of Mr. Milstein’s projects that combined a house with a camping tent. Both designs were published in Lester Walker’s seminal 1993 guide to small living, “The Tiny Book of Tiny Houses.”

Today, the Bolt-Together House is a rare species in the wild, a snow leopard for tiny-home enthusiasts. A YouTube video posted a dozen years ago of a shabby survivor in New Brunswick, Canada, has attracted more than 53,000 views.

All of which explains why the Warrens were besotted with the Delancey listing. “It was just a dreamy little place to us that was in our budget and so unique,” Ms. Warren said.

They were far from the only admirers, but were determined to have it. “We put an offer on it direct from Mexico, without even going to the town or seeing the cabin, which I think threw the Realtor for six,” Ms. Warren said, using a term derived from the game of cricket to describe the feeling of being whacked hard by a bat.

The sellers interpreted the couple’s pre-emptive bid of $85,000 as less a gesture of enthusiasm than of possible instability and accepted the second-best offer. As Mr. Warren interpreted the rejection, the sellers were afraid he and his wife weren’t serious and would “mess them around.” As fate would have it, he added, “a few weeks later, the second highest bidder actually messed them around.”

The Bolt-Together House was now the couple’s, a retreat where they could spend several months a year with their dogs, Taco, Margarita and Chili. But it still smacked of shack.

Had its builder followed Mr. Milstein’s plans to the letter, the walls would have been insulated and there would have been sanitation facilities. (The house would also have been 224 square feet.) Yet neither comfort in winter nor an indoor commode appeared to be a priority. Instead, there was an outhouse some distance away, in the meadow.

The Warrens installed insulation as well as baseboard electric heating. Their dream of a speedily acquired and affordable septic system, however, was dashed by the complexity of the site, with its creek, and by pandemic-related delays.

At that point, they discovered the Cinderella toilet, which incinerates waste with the push of a button. At $5,000, it was a comparative bargain. They put it into a new bathroom, along with a walk-in shower with glazed green wall tile.

Working with a local carpenter, they doubled the size of the kitchenette, from subatomic to minuscule. Its counters and cabinets are maple with brass hardware, and there is a two-burner electric cooktop and a dainty farmhouse sink.

The couple also expanded the size of the mezzanine’s sleeping platform to fit a queen-size bed. They put in Wi-Fi that they said works far better than their Wi-Fi in Tulum.

Outside, they laid down a driveway through the meadow and built a floating deck overlooking the creek.

The total cost of renovations, they estimated, was $60,000.

Recently, the Warrens welcomed Mr. Milstein, now 79, to check out the place. Despite the plaudits he received for his innovative shelter designs, he chucked the practice of architecture decades ago and now works as an aerial photographer with a studio in Kingston, N.Y.

“It was cute,” he said of the Warrens’ house. He understood why the couple had brightened the interior with white paint, although he described himself as more of a natural-wood man. He also understood the sacrifice of the ground-level sleeping area in his original design to make room for a bigger kitchen.

“It was surprising how comfortable it was, with four of us hanging out there,” he added, alluding to the Warrens and his girlfriend, Kim Cantine. Ms. Cantine “had the idea that she wants to find these around the country and photograph me standing in front of them.”

Living Small is a biweekly column exploring what it takes to lead a simpler, more sustainable or more compact life.

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