The bookshelves groan with Mexican masks and tribal figurines, the coffee table is choked with ornamental ashtrays and seashells, and you have to be careful not to trip over the carved wooden leopards and birds scattered across the floor.

This treasure trove of folksy trinkets might not sound like the lair of the 20th century’s most influential modernist design duo, but then Charles and Ray Eames – of whose work a vast retrospective at the Barbican opens this week – were no mean minimalists.

“It gave me great pleasure,” wrote Robert Venturi, the godfather of postmodernism, who has spent his career battling the modernist dogma of “less is more”, “that the Eameses reintroduced good old Victorian muddle in their home. The architecture of modernism always wanted everything to be clean and orderly and then along came these two, spreading their eclectic assemblages all over the entire interior.”

A treasure trove of folksy trinkets ... the living room at the Eames House. Photograph by Antonia Mulas, courtesy Barbican/Eames Office LLC

If Mies van der Rohe imposed rigid order on the world with his clinical creations, Charles and Ray Eames came and smothered it with patterned fabrics and scatter cushions. They humanised modernism, exuding warmth, colour and unbridled optimism in everything they produced. They sampled promiscuously from the world’s cultures, crossing conventional boundaries of taste with glee. As the British brutalist architect Peter Smithson, an Eames-admiring contemporary, put it: “They made it respectable to like pretty things”.

Their eclectic output, from the famous moulded plywood chairs (still in production) to immersive multimedia extravaganzas for IBM, now rambles through the Barbican in London, in one of the most comprehensive retrospectives of their work to date. It is a thrilling bazaar of furniture prototypes and kaleidoscopic animations, architectural models and yet more Mexican masks, all drenched with the Eameses’ uniquely sunny outlook – a sharp contrast to the Barbican’s dour concrete halls, the result of modernism when it hit our more cloudy climes.

The Eames House, as the cradle of their invention, stuffed full of inspirational ephemera, looms large in the show – not least in the clever exhibition design by 6a architects, who have made plinths and partitions from slender off-the-peg steel sections, echoing the lightweight industrial construction of the house itself.

Completed in 1949, as part of Arts and Architecture Magazine’s seminal Case Study programme of 36 model dwellings, their house was a low-cost collage of catalogue components, proving what could be done with a standard kit of parts. As Charles Eames put it, it was an experiment in “building something out of found objects, which is the nicest kind of exercise you can do.”

The materials weren’t quite scavenged from skips, but they had already been ordered for an earlier design for the site, a Miesian glazed bar raised up on stilts, which Eames dismissed because it blocked the views of the sea. “We realised we had designed the most minimal house with the most amount of steel,” he says, in a film on show in the exhibition. “We thought, why not make the biggest volume possible with the least amount of material instead?”

Nestled among eucalyptus trees on the bluffs above the ocean in Los Angeles’ well-heeled Pacific Palisades neighbourhood, the result is an impossibly paper-thin pair of boxes – and it’s still as startling today as when Architectural Forum published the project in 1950. “Life in a Chinese kite,” declared the headline. “Standard industrial products assembled in a spacious wonderland”.

1999–2015 … Oliver Wainwright re-enacts his teenage architectural pilgrimage.

Drawn to the seductive Eames mythology as a design-obessesed teenager, I first visited the house in 1999, when I dragged my parents and brother up the hill on a family holiday – only to find the place wasn’t open to unannounced visitors. Sixteen years on, it now receives 10,000 architectural pilgrims a year. For $10 you can peer through the windows to marvel at the life-size vitrine of Eames domesticity, maintained as an exquisite shrine, exactly as it was the day Ray died in 1988. ($275 gets you a personal hour-long tour inside.)

“We don’t want to fetishise it,” says Lucia Dewey Atwood, one of the Eameses grandchildren who looks after the house, as we stand beneath a shock of tumbleweed that dangles from the living room ceiling. “But it’s important to give people a sense of how much care they took over creating a setting to receive guests.”

The house was a carefully choreographed stage set for the couple’s riotous social gatherings, which often entailed the wearing of masks, performing of rituals and being a guinea pig for their latest chairs. One photograph in the Barbican exhibition sees Charlie Chaplin and Isamu Noguchi kneeling in the living room for a Japanese tea ceremony, while a page from Ray’s diary shows what circles they moved in. 23 April 1957 featured lunch with Sir Hugh Casson, chief architect for the Festival of Britain, followed by dinner with Billy Wilder and his wife – with a careful note to remember the presents: “Bonsai elm + hats!” As designer Don Albinson, who worked in the Eames Office from 1946-59, recalls: “It was all theatre. Every visit totally staged. Ray storyboarded it all in her head.”

Complete control … Charles Eames directs a photoshoot for Aluminium Group furniture. Photograph courtesy Eames Office

The sense of stagecraft extended from their private realm to every aspect of their public work. More than any other designers before or since, they exercised exacting control over their work, down to staging photoshoots and directing commercials. Just as she obsessively itemised every curio in their home, Ray kept a detailed list of objects to be arranged in showrooms, exhibitions and photoshoots, always bringing an unexpected touch – like the famous image of the bird nestled in among the wiry legs of their DKX chairs for Herman Miller.

The Eameses playful mischief is still evident in their home studio, the smaller pavilion that stands across a small courtyard from the house. Leaning up against the wall like a precarious stack of cards stands their prototype Music Tower, a gravity-powered xylophone, played by dropping a small ball from the mezzanine above. A replica features in the exhibition, providing an appropriately anarchic plinkety-plonk soundtrack to the riot of ideas. New employees of the Eames Office would be set the daunting challenge of rearranging the keys to make a new tune. As Charles Eames used to tell his staff: “Take your pleasure seriously.”