The complex mix of building use, changing and developing whilst the tower was under construction, required significant flexibility and robustness in the design which has exceeded commercial expectation.

Project Name: The Leonardo
Studio Name: Co-Arc International Architects Inc

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Consequently, an early decision was made to create a flexible approach to the integration of the structure and servicing, allowing construction to proceed at lower levels and to be augmented and refined as levels were added. Ultimately the building, is an honest reflection of its making. Structure and servicing to provide the range of uses have become an essential part of the concept.

Reflecting the use within and creating a threshold between inside and outside, with over 800 balconies and terraces, the external skin of the building is both an appropriate response to climate and social factors. The balconies and terraces are determinants of the expressed form of the building.

The structural grid was determined by a previous failed 40 storey development on the same site. The developers had left partially constructed bases for their columns and a mass concrete base for their core. Working within these limitations a new grid enabling founding on new foundations for a 55 storey building resulted in an articulated slender tower facing north south.

The orientation and layout of the plans provide flexible floor space at every level of the tower maximizing views and minimizing climatic effects.

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With due regard to South Africa’s high unemployment, to maximize safety and labour utilization, the building is largely constructed from concrete and masonry, with the external skin consisting of transportable components, assembled and erected from the inside.

Its ground breaking use of engineered ‘stone’ as a cladding material allows for a lightweight perimeter skin that forms a weather shield and creates shaded deep recesses for glazed balconies at every level: The refinement of the detailing and careful consideration of materials results in an apparently simple yet timelessly elegant façade.

The public is welcomed into the building via a triple volume arcade and a series of ground public rooms to a variety of public facilities including 8 restaurants/ bars, the 5th floor podium terrace, a sky lobby as

well as the 55th floor sky-deck. Other public uses are the gymnasium and health spa, retail shops, conference venue and crèche.

The development eventually evolved into a mixed-use 55 storey building. The result was derived from an exploration of establishing the parameters that dictate what the building will become; test the possibilities; aspire to make a contribution to the wellbeing of users and a positive difference to outsiders; use resources wisely; be as honest to the expression of structure and servicing as you can; ensure that local cultural, social and climate conditions are considered. In order to make the building timeless, distil each element to its essence. In the end the building should reflect these concerns, thereby deriving value for the client and making a contribution for society.

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The basement is made up of four floors, housing the parking facilities, storage for tenants as well as the core services. The podium is made up of 9 floors which holds the public facilities, additional parking, back of house servicing and offices as well as services. The public facilities are made up of retail, reception areas, conferencing facilities, bars, a café, a restaurant with its own playground adjacent to a half Olympic sized pool, a crèche and outdoor playground, a private dining area, a wine cellar, a chefs garden, a gym, a spa and a main bar with a sunset terrace. The tower, rising above the basement and podium, consists of offices, apartments, a hotel and reception, penthouses and the 3000m² Leonardo suite spread over 3 floors. Right at the top of the building is a viewing deck which evolved into a high-end bar. The occupancy of the building was ultimately determined by what the building became.

All public facilities of the building are fed off Maude Street by means of an expansive triple volume colonnade with vast glazing opening into the retail spaces. The colonnade pulls people through the space at street level, whilst people take cover. The reception areas as well as conference facilities are located on the upper floor above the entrance level which are accessed by lift, stair or escalator. The top of the podium opens up to a deck with a swimming pool and the main public facilities.

The building is a realisation of South Africa’s market driven forces. There was no final client approved design, instead the building was a manifestation of its making, its uses, height and occupants.

The building was also a product of the realisation that to resolve South Africa’s challenges, the country will need to look towards the rest of the world, while also dealing with rapid urbanisation that is currently taking place in the country. The ever-changing and evolving design of the Leonardo which was an on-going, close and interactive process of workshops with the client, solves issues relating to urban mobility and density, providing a destination for capital, both local and foreign.

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The process at arriving at the final product which inevitably became the client approved design, was achieved by a close collaboration with the client. During design and construction of the Leonardo, the client encouraged an exploration of methodologies at arriving to a design as well as to develop and explore the materiality of the building.

This evolution required an unusual design process and facility to provide regularly updated drawings reflecting each possibility for sales team feedback; funding appraisal submissions; construction drawings; site development plans; and building planning submissions. These designs were constantly being updated, so much so that it become something of an on-site quip that the architects would know what the building looked like when it was finished.

A previously failed development on the site had left an abandoned excavation with a dangerously aging lateral earth support system, and mass concrete foundations. Site geology, including a diabase dyke and groundwater seepage through rock fissures exacerbated adverse constraints. The Leonardo design accounted for the retention of existing bases. An east-west orientation of the core allowed the engineers to straddle unusable underground relic structures, and at the same time enabled a largely column free tower plan with perimeter columns and predominantly north and south facing facades maximizing views and minimizing climatic effects.

As part of the brief, the manufacturing and installing of materials needed for the building was to be labour intensive to respond to the high unemployment rates in the country. This was considered during the design process to ensure materials and products that were used could be installed by labour, instead of assembled in a factory. In turn the number of jobs on the project would boost the economy. The construction team was made up of 3000 people at its peak and 18 000 – 20 000 employment opportunities were created through materials supply chain, manufacture and industry.

The economics of the construction also came into play in the location and orientation of the core of the building, which together with the perimeter columns carefully avoid the foundations from the failed former project. As the primary structure of the building, and operating within the constraints of the site, this skeleton also dictated a long and thin north-facing building.

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The core of the building, placed centrally on plan, contains five lateral spine walls providing for the essential structural support to the entire cross-section on all floors. These spine walls form the backbone of the building. The five spine walls are extended above the roof level, symbolically identifying and celebrating the essence of the structure of the building. The viewing deck slab is hung from the five lateral spine walls with beams tying back to the walls. The accessible portion of the viewing deck is set back from the edge to avoid guests looking down onto the Leonardo Suite deck below, as well as sound travelling down to the suite.

Adding to this backbone, the architects made use of interstitial double volume spaces which were located at eleven floor height intervals seen within the total section of the building and read as breaks or bands in the façade. Furthermore, the interstitial zones are identified by the exposure of the structural columns providing further evidence in the making of the building. These spaces house the working mechanical and electrical plant rooms necessary for the building’s operation. The technical facilities, such as the air-conditioning plants, water tanks and electrical substations are accommodated within.

These double volume interstitial areas also function as lateral structural supports, acting as beams enabling the vertical loads to be carried back from the outer face of the building to the core, in the event of column failure at the perimeter, thus ensuring ultimate vertical loads could be transmitted to the ground. Careful organisation of structure with vertical services and a strategy of doubling up services required by each of the different uses within the building, including lifts, in vertical shafts in the spine ensured an extremely economic ratio of useable and service floor space.

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Structural challenges on the podium required the tower support structure to be off-set due to structural and modular demands made by the parking decks below.  It dictated the architecture at this junction and resulted in a dramatic triple volumetric space, a memorable and unique architectural statement. 11m high ‘Keyhole’ columns were designed as transfer columns, located at the base of the tower to carry the structural load of the northern façade down into the footings. The space houses the main restaurant and allows opportunities for the public to experience the sheer magnitude of the building through the scale and proportions of the columns.

Co-Arc International Architects Inc


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