A cushioned bench hangs over the water at the end of a wooden deck, projecting from a low timber-framed house that hovers on the edge of a pristine sand-spit. A freshly peeled orange rests on a table and, through an open door, you can make out slender steel-legged furniture silhouetted against the gleaming sand. Casually strewn sandals and a book await the well-leisured occupant, while a rowing boat bobs in the background.

This sun-drenched image of a modernist Robinson Crusoe dream was splashed across a full page of the January 1951 issue of Architectural Forum, oozing the postwar promise of free-and-easy indoor-outdoor living that beckoned in the Florida city of Sarasota. Named best house design of the year by the American Institute of Architects in 1948, the tiny Cocoon House was the most distilled vision to date of the architectural practice of Ralph Twitchell and Paul Rudolph, a partnership that had created a buzz around this sleepy beach town with a series of dazzling modernist holiday homes.

With their simple, lightweight frames, large expanses of glazing, open plans and blurring of inside and out, their little houses embodied a romantic ideal of the primitive hut in the untamed subtropical wilderness. These were pioneer cabins on virgin land, offering a chance to live the carefree beach life in your own piece of paradise.

Facebook Twitter Pinterest Pioneer cabin fever … a replica of the Walker Guest House by Paul Rudolph. Photograph: Anton Grassl

Seventy years on, the exotic thrill is no less palpable, as a trolleybus disgorges a herd of architectural tourists into the little house as part of the annual Sarasota Modernism Weekend, which this year celebrated the centenary of Rudolph, who would go on to become one of America’s greatest architects. Now known as the strong-willed maestro of expressive (and often controversial) concrete hulks, such as Yale’s Art and Architecture Building and Boston’s Government Service Center, Rudolph began his career at the opposite end of the scale, crafting diaphanous beach homes that looked as if they might drift away on the coastal breeze.

Trundling along the languid, palm-fringed roads of the appropriately named Siesta Key today, the trolley bus takes in the handful of modernist gems by Rudolph and his followers that still cling on between the neoclassical McMansions that have sprung up in the ensuing decades. The 50s structures seem all the more delicate in the context of their chubby neighbours, and it is hard to imagine a time when they were just cabins on the beach, free from high stuccoed walls and electric gates.

Facebook Twitter Pinterest Naval inspiration … the Cocoon House. Photograph: Jenny Acheson

The humble Cocoon House, which was built as a guest house for Twitchell’s in-laws, became widely known not only for its pristine setting, but for its technological innovation. Entering the Portakabin-sized building, the first thing that strikes you is the curved roof, which droops above your head like the canvas of a tent. It is the result of slinging a row of thin steel straps between the wall posts, covering them with flexible insulation, and then coating the resulting sandwich with spray-on plastic foam. The unusual process was inspired by a technique that Rudolph had seen used to mothball ships for storage in the Brooklyn Navy Yard, where he spent his military service during the second world war. The young media-savvy architect wasn’t going to miss an opportunity to publicise his novel use of this newfangled product.

“Watch this building being wrapped in Cocoon!” trumpeted a billboard outside the construction site at the time, along with the words “government specification” and “operation mothball”. The ruse worked. Crowds gathered to watch the process and handfuls of lifestyle journals cooed over the result. No matter that the experimental roof soon leaked and had to be replaced with more conventional materials.

“Rudolph was very good at being published,” says Timothy Rohan, author of the definitive tome on the architect’s work. “He developed very good relationships with editors in the US and Europe, and understood the power of drawings and photography.” He produced dramatic sectional perspective illustrations of his designs, which often took on a life of their own, even if the house was never built. Rudolph worked with renowned photographer Ezra Stoller to meticulously stage his completed interiors for photoshoots, borrowing modern furniture and props to dress the spaces.

Facebook Twitter Pinterest Supersize my villa … Ralph Twitchell’s Revere Quality House with huge 2007 extension added on. Photograph: Oliver Wainwright

It was a technique he had learned a couple of years earlier with the Revere Quality House of 1948, a building designed to showcase the products of the Revere Copper and Brass Company in an airy modern setting. It set the tone for much of what would follow, with a six-inch thick concrete slab roof held up on thin steel columns, allowing walls to be placed anywhere, and full-height “jalousie” windows of parallel glass louvres to allow cross-ventilation. Sixteen thousand people came to see it upon completion, marvelling at the polished terrazzo floors, top-lit interior courtyard, screened porch and fitted cabinetry, all billed as fireproof, termite-proof, hurricane-proof and mildew-proof. It has survived, but at a cost: it now serves as the diminutive porch to a grossly oversized pseudo-modernist mansion, grafted on to its backside in 2007.

There was a carefree openness that made anything seem possible

“These houses had both the good fortune and misfortune to be built on very prime real estate with great views of the water,” says Rohan. Their small size has made them vulnerable to redevelopment and many have been bulldozed and replaced with heaving piles in the favoured Mediterranean revival style. But, for a time, Sarasota was the unlikely home of avant garde experiments. The noted critic Henry-Russell Hitchcock wrote in Britain’s Architectural Review in 1952 that the greatest contemporary architecture in the world was being done by a group of young architects in Sarasota.

“There was a carefree openness here that made anything seem possible,” says Rohan. “Sarasota was a vacation spot for a well-off, cultured, cosmopolitan crowd. These were holiday homes, so clients could be more experimental. They would come here for their modernist interlude, then go back to their big colonial house in the suburbs of Chicago or New York.”

Facebook Twitter Pinterest Paul Rudolph working on the Umbrella House. Photograph: Sarasota Architectural Foundation/MOD

These buildings had a promotional role, too. One of the boldest was the Umbrella House, commissioned by the wealthy developer and architecture enthusiast Philip Hiss in 1954 as a habitable billboard to promote his new Lido Shores development. Standing like an etiolated classical temple at a prominent crossroads, with long columns holding up a wafer-thin canopy above the house and pool, it was a model of Rudolph’s ability to fuse modern forms with vernacular climatic elements. In the south, before refrigeration, it was common for homes to have a dairy shed for perishables, in the form of an outbuilding covered with a secondary roof for sun-shading and airflow. Rudolph simply scaled this principle up, erecting a canopy of tomato stakes laid across wooden joists, which oversailed the whole complex.

Once again, it caught the popular imagination: 2,500 people showed up on the opening day, at a time when Sarasota’s population was around 25,000. Hiss was elected to the Sarasota school board the same year, and set about securing Rudolph commissions for a couple of the city’s high schools, one of which survives and was recently restored in gleaming white glory.

Destined for bigger things, Rudolph left Sarasota in 1960, but his colleagues continued in his footsteps, cementing the reputation of the “Sarasota School”, which flourished for a few more years until the tide began to turn against the modernist dream. With the advent of air conditioning, the free-flowing, open-air style became less attractive, while increasing conservatism saw a return to cutesy revivalism. As critic Michael Sorkin puts it: “As the 60s progressed, America lost the confident lightness of functionalism as it careened into a fresh baroque of stupid prosperity.”

In an article titled “Whatever happened to Sarasota?” in a 1967 issue of Architectural Forum, Hiss lamented the fact that the city had “almost completely surrendered to the big developers … There are a number of multimillion dollar projects under way – all of them concerned with profits, none of them with architecture.”

Sarasota’s steady architectural decline has continued as the city’s fabulous wealth has increased. Its residents now live in leafy gated communities separated by sparsely populated strip-malls either side of six-lane highways, along which they can drive to events that celebrate the dream of a minimal modern lifestyle that once was – for $150 a ticket.