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The two wings are connected by what the architect calls an “umbilical cord”—a glazed corridor that steps down slightly with the slope of the site.

The branches of the trees reach up and over a flat concrete roof, which is planted with wavy grass, essentially lifting what would have been on the ground up a level and adding to the greenery. “When you drive in, you see the grass on the roof, and it looks like the house is underground,” says Toni.

Floor-to-ceiling glass walls let the outside in, especially when they’re opened up, transforming the house into something more like a garden pavilion, the interiors becoming part of the garden itself. At points, the trees are so close they seem as if they’re inside; sections of the eaves had to be cast with cut-outs through which the branches could grow.

Nevertheless, Katz considers the design to follow a fairly typical double-storey model, with bedrooms upstairs and living space downstairs—but flipped onto its side. This way, all the rooms face north, so they have lovely natural light and are warmed by the sun in winter. Meanwhile, the deep eaves keep direct sun out in summer and shield the windows from seasonal thunderstorms. Every single room opens out onto the garden.

The result is “almost like a resort”, as Katz puts it. “Joburg has the most amazing country feeling in the suburbs,” he points out, so it’s actually quite an appropriate response: a real suburban sanctuary, so self-contained you could be almost anywhere.

While the house’s configuration might have been dictated by logic and necessity, Katz has found opportunities to exercise his creativity in all sorts of ways within the design constraints.

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The roofs might have been flat, but he’s played around with changes in volume by changing the floor level. The large, open-plan living area, which includes a lounge, kitchen and dining room, opens onto an outdoor sunken lounge with a barbecue and pizza oven. “There are a lot of ‘70s influences,” Katz says. A skylight above it seems to open to the sky, exaggerating the sense of height.

In the living room, skylights have been hidden at the edges of the rooms to let in “slits of light” from above, washing particular walls with light without revealing the source. Katz made the skylight in the centre of the room in a parallelogram rather than a rectangle. It’s a bit of a visual pun, because rectangular skylights cast parallelogram-shaped blocks of light.

Another key part of Katz’s approach is his love of brick as a building material. “Face brick tones so well with our environment,” he says. It’s the same colour as the ground.” All around Johannesburg, the soil has a ferrous tinge, so bricks “somehow feel more relevant than some kind of imported colour palette”.

This is apparent especially at the house’s entrance, which necessitated solid walls for privacy, where Katz has played around with various bricklaying patterns. He’s used bricks to design breezeblock “veils” and parapets for the roof garden. At other points inside, he’s used variations in colour and has created built-in shelving. They’ve been sliced thin to create skirting and bathroom tiles. There’s a textural richness and expressiveness that seems filled with infinite possibilities.

“You’re placing materials on the site, so you can either have a flat surface or you can articulate it and have it function as something else, either visually or functionally,” he says. “So that’s become the principle of the house. Repetition and difference. The materials repeat, but you use them in different ways.”

This is not just an aesthetic precept. “I think restraint is a good design principle,” Katz explains. As Toni notes, it also means that you bring less onto the site, forcing you to “think outside the box”.

“You’re not overconsuming; you’re not overdoing things,” the architect adds. Instead, the self-imposed restriction compels you to design every aspect of the house “with care and thought”. Quite simply, it serves to “yield a better product”.

It’s an approach that also puts a somewhat different spin on the less-is-more old modernist maxim. Rather than leading down a path towards minimalism, in Katz’s hands, it becomes a rich, tactile and expressive approach which proves that using less might yield a whole lot more than you expected. The walls practically vibrate with creativity, mystery, delight and fun.

Toni’s response in furnishing the house, too, is highly sympathetic to the architect’s approach. She didn’t add objects and furnishings needlessly. “The structure speaks for itself,” she says, “so you don’t need to add anything. When simple is done well, it’s the best.”

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She also sought out locally designed and manufactured furniture wherever she could, as much to keep the carbon footprint low as to celebrate local skills. This effort yielded a kind of easy elegance, a resonance that isn’t too self-conscious or overdetermined. And because the furnishings are local, the look and feel of the interiors impart a subtle sense of place.

You could say the same for the house. While superficially, it might look like an homage to mid-century modernism, it is actually a dazzlingly complex and highly original response to Johannesburg suburban life. And, like all the best modernist designs, it is deceptively simple-looking.

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