London Zoo's Snowdon Aviary reinvented as Monkey Valley – ADC

Looking south from the top of Primrose Hill, the Snowdon Aviary at London Zoo has been a distinct and delightful feature of London’s skyline since it first opened to visitors in 1965. Designed by Antony Armstrong-Jones (1st Earl of Snowdon, former husband to Princess Margaret, hence the title) with architect Cedric Price and structural engineer Frank Newby, the building was intended to last for no more than 30 years, on the architect’s astutely anticipatory assumption that zoological practices would undoubtedly have evolved and, as such, the enclosure would require a rethink for new inhabitants.

The aviary was home to a variety of exotic birds, its carefully gauged mesh designed to keep the larger, more unusual, varieties from the subcontinent in, and the common local birds, such as starlings, out. The residents’ welfare was paramount — the design having maximised the volume through the deployment of the triangulated envelope. But more than 50 years later, husbandry practices had indeed moved on, and the structure became due for a refresh.

Bird and animal captivity is now focussed on preservation rather than display, and providing safe, sustainable conditions for species to thrive and breed. To that end, in August of this year, with the birds relocated, the Grade II listed aviary was newly restored, repurposed and refurbished as a home for a troop of ten Eastern black-and-white colobus monkeys. Renamed Monkey Valley, this is the zoo’s latest attraction, a so-called ‘perfect pad for primates.’

We will come back to our furry friends in a moment, but there is so much more to reveal about this truly unique architectural curiosity. Hovering just above the treeline, the gravity-defying structure never fails to surprise and remains the only example of a tensegrity structure in the UK, contributing to its listed status.

The aviary captures something of the explosively imaginative surge of activity that emerged out of London in the 1950s and 60s. In music, jazz and rock-and-roll took hold, influencing image-making in art and design. In politics and the economy, the country saw a period of growth and optimism, with rising living standards and emerging markets, such as rapidly increasing car and home appliance ownership. In architecture, post-war clearance of swathes of destruction offered new ways of occupying the city, with many housing projects, offices, shopping centres and public buildings constructed from then new and cost-effective prefabricated concrete systems. Cool, contemporary London venerates that Brutalist portrait, icons of which can be found in Erno Goldfinger’s Balfron and Trellick Towers, and also at London Zoo in the shape of Hugh Casson’s handsome Elephant House.

Meanwhile, in some areas of the profession, architects were investigating forms of prefabrication that could offer more lightweight construction solutions. Whilst civic infrastructure sought to be represented in robust forms of construction, other parts of society were embracing concepts of time and temporality with a boom in modular design systems using plastics, fibreglass, inflatables and pressed metal panels for both mobile and static enclosures. This strand of design came out of a seemingly contradictory mix of materials innovation in industry (chiefly petrochemical) combined with a social and subcultural concern for ecology, energy and finite resources.

It was the latter to which the architect-polymath, Richard Buckminster Fuller devoted his life’s work. His magnificent global Design Science Decade project (1965-75) sought to chart all the world’s natural resources, from mineral deposits to energy, asserting that they be better deployed towards ‘livingry’ not ‘weaponry’, and 100 per cent redistributed for all humanity. Fuller was an incredible networker and the findings were collected by individuals and schools of design and architecture and published in a number of volumes — pre-internet of course. It’s hard to imagine what Fuller would have achieved had he had that tool at his disposal too.

The spatial expression of Fuller’s search for an ultimate economy of means emerged from his study of the systems and sources in nature and embracing of ‘nature as technology’. His Dymaxion house, car, map and dome, amongst other artefacts, embody his design ambition for ‘maximum gain of advantage from minimum energy input’. Fuller’s word Dymaxion is derived from: dynamic, maximum and tension — and a tensegrity structure is its principal method of construction.

Fuller’s deep understanding of the inherent geometries in natural structures (think spider’s webs, shells and the molecular make-up of carbon) meant he could design structures for humans that were demonstrably stronger, lighter and used less material compared to more ubiquitous construction methods using this system. The term tensegrity (tension and structural) is also attributed to Fuller; “a self-tensioning structure composed of rigid structures and cables, with forces of traction and compression, which form an integrated whole.” Sculptor, Kenneth Snelson was a student of Fuller and has long claimed that he had originated the idea of ‘floating compression’. What is pertinent here is that the word tensegrity is firmly lodged in the vocabulary of designers and engineers from architecture to molecular biology. The enigma of it is that in tension, the whole structure appears to float; cut one cable, and the whole thing collapses.

It is no coincidence then that Fuller was a huge influence on Cedric Price’s thinking, and was both a friend and associate having been introduced by the aviary’s engineer, Frank Newby. Newby cut his teeth as the youngest ever partner at F J Samuely and Partners on Powell & Moya’s elegant sculptural Skylon, an emblem of the 1951 Festival of Britain. At the time, the Skylon was the only tensegrity structure in the UK, and whilst it was not inhabitable, it was a thing of immense beauty and engineering wonder. Its name was also a portmanteau – sky (towards which it pointed) and nylon (a remarkable modern material in 1951).

Back to the birds: the initial commission for the aviary was won by Armstrong-Jones who had designed a small hexagonal bird cage for the Queen Mother. The secretary to the London Zoological Society had seen the charming but rather conventional timber pavilion on a visit to Windsor and offered Armstrong-Jones the job. Armstrong-Jones had studied architecture at Cambridge but was not a qualified architect, so the zoo’s architectural advisor, Hugh Casson appointed Cedric Price, also a Cambridge undergraduate, alongside Newby.

The notion of deploying a tensioned structure came early in the design process. Early sketches by Armstrong-Jones show bridge elements that seem to hang at tree top level, and he is photographed putting finishing touches to a cardboard model (which made a guest appearance in the 2016 Netflix drama series, The Crown), but the resolution of the structure was clearly developed by Price and Newby together. There are several pages of their combined sketches that chart the design’s evolution into the elegant solution of the four ‘floating’ corner tetrahedra and two leaning triangular columns all connected by tensioned cables that can be seen and celebrated on site today. The internal volume provided the maximum free span and flight area across the sloping site – meeting an essential design criterion.

Another central aspect of the original design – intended to meet the requirement to offer the best possible public observation of the birds – was the introduction of the pedestrian footbridge and an invitation to visitors to walk through the enclosure (only the second walk-though zoo exhibit in the world at that time). The double-cantilevered, pre-stressed concrete bridge, again, appears to defy gravity as it lifts viewers into the space, ground sloping away beneath, and with a tiny ‘built-in’ bounce makes for an utterly delightful immersive experience. Price’s intention was to design something “not only mov[ing] in such a way that it might excite school children with an element of danger – who are bored of looking at the birds – but it is placed in such a way that the birds themselves are not disturbed by the people being inside.”

Following the aviary’s 50th anniversary in 2015, and in recognition of the fact that the colobus monkey had all the attributes to be the perfect new resident, an initial scheme was drawn up by Foster + Partners that proposed an equally mesmerising extension. Like a long stretched net sock which knitted sideways through into the existing cage, the design brought both the architectural and technological motifs up to date, as well as offering a sympathetic environment to view the animals. Lord Foster had provided the work pro-bono.

His friendship with Buckminster Fuller and admiration for his work is well known, so to develop a new architectural response using the latest materials and digital modelling tools was a sensational opportunity which has been sadly missed. Unable to secure sufficient funds, a value-engineered scheme was taken forward by ZSL build partners, CBRE, who broke ground in 2020.

CBRE’s work has been to faithfully restore the existing structure, starting with the replacement of more than 200 panels (3,800 square metres) of mesh with a more flexible stainless steel net: ‘Jakob Webnet’ supplied by German Company Pfeifer.

This has been sewn together with steel thread and is much closer to Price’s original intention for a material that had a degree of flexibility and movement. The original panels had been the Achilles heel of the project in its early days, the crimping tool supplied to the contractors to connect each panel were never quite up to the job. Buckminster Fuller had visited the building just before its opening and had expressed his concerns about the connections in a letter to Newby, although gradual replacement over the years was managed.

Now, the aluminium tetrahedra have all been cleaned and all cables replaced. Thoughout the work, the entire structure remained erect by using temporary cables, whilst old ones were removed and new ones installed. The concrete of the footbridge has been restored as have new movement connections to maintain the bounce.

All ground works have been cleaned and the timber of the original handrail restored with the addition of some mesh for safety. The entrance and exit vestibules have been upgraded to be more robust for its new inhabitants, but their shape and material are faithful to the original design.

Where Foster’s extension scheme appealed to the human eye and enthusiasm for invention (who knows what the monkeys feel about these things), CBRE’s addition at the rear of the site is wholly utilitarian and in the service of the monkeys and their keepers. Whilst it seems to meet the needs and functions of the different occupants, this enclosure is demure to the point of being invisible – but one senses this was not the intention.

It is likely that Price would have enjoyed the attributes of both schemes: Foster for his technological ambition and CBRE for its pragmatic and unadorned response. Whilst not so obvious to see where moments of joy lie in its own scheme, the team has worked well to retain the inherent delight in the features of the original building – allowing it to soar through our skyline for many decades to come.