primary shapes

Beauty comes in all shapes and sizes – a notion that holds true for this unique residence in the northern suburbs of Johannesburg.  

This home can be aptly described as an ever-evolving architectural marvel. It takes on a transformative journey, morphing through a series of geometric shapes, commencing with a triangle and culminating in a circle. 

Design inspiration 

Displayed through a large semi-circular window is a magnificent Chinese nettle tree. Making this the focal point, informed how the house would be positioned on the 1 600m² plot of land. The concept for the house originated from a book that architect Greg Katz of Gregory Katz Architecture was engrossed in at the time – Euclid’s Elements 

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The semi-circular window looks out onto the Chinese nettle tree, which is the focal point of the home.

Captivated by the idea of creating a structure where the exterior of each shape is composed of different materials, while the interior materials remain consistent, thereby unifying the spaces, Katz sketched a rudimentary digital diagram that incorporated various shapes such as triangles, hexagons, cubes and circles – an infectious idea that prompted the clients to suggest the inclusion of trapezoid windows.  

Materiality follows form 

The choice of material was made in response to the shapes themselves.  

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Great Primary Shapes House – a home composed of triangles, hexagons, cubes and circles.

  • Triangle entrance: This was achieved with concrete, poured in at both angles to produce this unique element of the house. 
  • Cube: Cement masonry units (CMUs) were used to form the garage and office structure’s perforated wall. These are usually placed in a running brick, but here are opened in a larger scale than usual for a breeze-block wall. 
  • Hexagon: Constructed with a 45-degree angled cant brick to achieve the shape. The finish of the face brick also delivers the required crispness that suited the form.  
  • Circle: Plastered with a Tyrolean render with its distinctive stippled finish, this rough texture provides a contrast to the cocoon-like interior. 

Wonderful windows 

Since the design unfolded from the outside in, it became one of the most unconstrained projects in the practice’s portfolio, devoid of any fixed formulas or constraints. It introduced a layer of complexity that sparked debates and required continuous resolution throughout the process, particularly the unusually shaped windows.  

“The semi-circular or smiley window overlooking the Chinese nettle is about 4m in diameter, so rolling the aluminium to take that form was extremely challenging,” says Katz. “The diagonal lines of the trapezoidal windows created a feeling of giant infrastructure that is being inhabited. But it took a lot of thought to work out how they would open and operate in the space.” 

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Even the trapezoid-shaped windows express their own geometry, creating a sense of living within a giant infrastructure.

Taking shape 

The outcome is a four-bedroom dwelling that not only fulfils its functional purpose but also aims to exude a joyful and captivating ambiance. Interconnected living areas create a sense of cohesion, seamlessly integrating with the outdoors through strategically positioned geometric aperture windows. The architect intended to invite exploration and delight in every corner, captivating the imagination with its progressive metamorphosis.  

The house’s distinctive charm lies in the fact that its skin doesn’t require paint – each shape is possessing and facilitating its own unique identity and distinctive character. A triangular entry volume houses a staircase that climbs at the perfect 3D angle, following the contour of the wall.  

This non-axial placement allowed space for the entrance door at the base of the stairs, creating a fascinating association and harmony between the floor plan and section. 

Living with nature 

The flat concrete roofs of the hexagon and circle used greening to insulate the structure. Usually, this would include a waterproofing layer followed by a root barrier to protect the roof from the ingress of roots. However, Katz employed an innovative solution of a crystalline admixture in the concrete of the roof slabs.  

Through a chemical reaction with water, this admixture achieves self-healing and sealing of cracks within the concrete, thereby making it waterproof and resistant to damage from plant roots. A 100mm layer of soil was placed above this and planted with tall grasses. 

Interior design 

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Form determined materiality, with the shapes constructed from a perforated screen wall of CMUs, rich red face brick, cement formwork and Tyrolean plaster render.

Having worked on the client’s previous residences, interior designer Cecil Cameron has a deep understanding of their style, preferences and distaste for the ordinary. Thus, it became a matter of harmonising their distinctive style with Katz’s architectural vision. To accommodate the unconventional room shapes, the team opted for a significant amount of custom-made furniture and pops of colour, enhancing the space’s uniqueness.  

Katz attributes his inspiration to his earlier experiences working with renowned architects such as Zvi Hecker and Daniel Liebeskind. He says: “Working alongside visionaries like Zvi and Daniel teaches you to embrace bravery, boldness and independent thinking.” The GPS House embodies that sentiment and stands as a testament to its uniqueness, courage, boldness and sheer excitement.  

Project name: Great Primary Shapes House. 

Location: Johannesburg, South Africa. 

Architects: Gregory Katz Architecture. 

Area: 275m². 

Photographs: Elsa Young. 

Interior design: Cameron Collective. 

Full acknowledgement and thanks go to for the information in this article.  


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