KleinJAN is the deserved winner of Cement & Concrete SA’s 2022 Fulton Awards in the “Building less than R50 million” category – not for its objective visible concrete interventions but rather its concealed hidden pragmatic innovation, situated in the vast open Kalahari Desert savannah.
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The judges were intrigued and impressed enough by the quaint KleinJAN Restaurant, in the vast Tswalu Private Game Reserve in the Kalahari, to make it the recipient of the Fulton Award in this category.
The unusual project was entered by the contractors, Kobus Duvenhage Bouers. KleinJAN – owned by South African Michelin Star chef, Jan Hendrik van der Westhuizen – was created on the site of a century-old farmhouse and is one of the smallest concrete structures to win any category in the Fulton Awards’ 43-year-old history. The intimate restaurant features an underground dining room.
The project brief was to embrace local products, with minimum interference with the natural ecological cycles of the region. Extension and inclusion of the diminutive 100-year-old farmhouse, Boscia House, were required without changing any features.
Climate requiring innovation
Sustainability being a key consideration, research showed a submerged building would require less energy to keep cool in the heat of the day or warm in the chilly desert nights. The decision to set the restaurant into the earth was not only for the utility of hiding the structure but also due to the known benefits of “thermal lag”, found in pit agriculture.
The concrete innovation is concealed in the earth. Although it is an intervention that cannot be objectified for its physical features above the ground, the role concrete played was far more important.
Thermal performance and comfort levels to sustain a full-fledged restaurant in the dead heat of the Kalahari Desert were the challenges. The entire structure, apart from the reservoir entrance, had to be submerged into the earth. It was built in Kalahari sand – an unstable and raw foundation, creating a concrete shell and basement and rehabilitating the sand, dunes, soil, grasses and vegetation over it.
Concrete to bind the spaces together
Concrete was used to structurally bind all the spaces together – from the reservoir entrance to the wine and root cellars and finally, the main restaurant. The design intent was always to have indoor and outdoor spaces to flow seamlessly into each other.
The restaurant was essentially built as a reinforced underground reservoir – i.e., not to contain water from the inside but the outside only. On the inside, only all the architectural features of a restaurant would be visible, and at no point will see concrete, however, concrete was chosen for multiple reasons.
The structure had to withstand dead (sand) and live (large animals such as buffalo herds) loads and be watertight from the outside.
Construction began by removing the top layer of windblown sand onto an in-situ calcrete formation. Some of the calcrete bank had to be removed to make the structure fit in the excavation. Soilcrete with rebar anchors were placed into the reinforced concrete structure below and behind certain retaining walls on the outside.
Thereafter, construction of the reinforced concrete basement floors, walls, columns, beams and roof flaps commenced. Portland grade 30/19 concrete was mixed by an on-site batch plant, reaching the required strength after the normal period of 28 days. Several specialised products and admixtures were used during the construction.
“Petrichor”, the name given to this reservoir, is the distinctive scent that accompanies the first rains. The circular water reservoir entrance to the restaurant houses a spiral staircase made of timber sleepers hanging from steel rods of the reinforced concrete roof, also designed as an underground reservoir. In the base, a water pool was formed in the reinforced concrete with a pump circulating the water to the roof, thus dripping in a circular form from the roof, creating a special effect.
The long passage with a barrel-vaulted roof and cellar leading from the “Petrichor” and dripping staircase from the restaurant was lined with bricks on the inside, giving it a farm-like feeling. The service kitchen and cellar passage to the restaurant underground was lined with reinforced concrete retaining walls on both sides.
One of the biggest challenges was to cite the building underground in such a way that it allowed them to open the restaurant facade to the view and cover the lid with earth that makes it look like a low dune in the landscape of a relatively flat site.
Another challenge was that the site is surrounded by ancient Boscia or Shepherd trees, so the team had to carefully plan around the trees and make sure their roots were not disturbed during excavation. This project, where concrete was used to structurally bind all spaces together, leaves a lasting impression of the small, yet thoughtful, details in service or design.
TEAM: Category: Buildings up to R50 million value Submitted by: Kobus Duvenhage Bouers (Pty) Ltd Client/Developer/Owner: Restaurant JAN Project Manager/Principal Agent: Tswalu Kalahari Reseve Structural Designer: MVD Kalahari Consulting Civil & Structural Engineers Architect: Savile Row Tailored Environments Concrete Supplier: Olivier Construction (Concrete Division)
For more information, contact the CCSA Information Centre (https://cemcon-sa.org.za/issues/issue169/): Tel: +27 11 315 0300 Website: www.cemcon-sa.org.za