IN PICTURES | A huge conservatory is at the heart of this Pretoria home

"It's not supposed to look like a barn," says architect Nadine Engelbrecht of the house she built for her parents in Zwavelpoort outside Pretoria. "It's just supposed to be a shell."

The house, on a 35 hectare farm with rocky, hilly grasslands and wide-open views of the nearby Bronberg mountain range, might appear to be referencing barn-like structures or gesturing towards some sort of agricultural vernacular design, but that wasn't Engelbrecht's primary concern.

When she first began sketching designs for her parents, Charmaine and Andre Freyer, she had no shortage of ideas - "architectural ideas", she laughs. She suggested screens perforated with images of the surrounding landscape and other aesthetic devices, but her parents weren't biting.

After a few more attempts, she asked her mother to show her a picture of something she liked. Charmaine produced a picture of a farmhouse in the Karroo - the semi-desert scrubland of the Western, Eastern and Northern Cape provinces.

"It looked like nothing," says Engelbrecht: a stone cottage with a roof of corrugated iron sheeting. "I asked her what she liked about it, and she said she didn't know."

She also showed her a picture of a tearoom in a conservatory that she liked.

Baffled, Engelbrecht went back to the drawing board. And then the penny dropped. "I realised my mom wanted simplicity," she says. "Nothing that's trying to look like 'Architecture' - just something that creates beautiful space and light."

So Engelbrecht took the simplest form she could imagine - the archetype of a child's drawing of home - and honest, humble materials, and started there. She designed a steel and glass facade, exposed concrete slabs and the closest thing to a stock brick she could practically use, cement-washed. The durable metal roof sheeting, she says, was a practical choice, interspersed with polycarbonate, which lets in natural light.

"We wanted to keep it rough and natural, like it belongs here," says Engelbrecht. Timber accents throughout provide a sense of warmth, at the same time softening the industrial materials.

The house was positioned to capture views to the north and south and overlooks a nearby grove of trees to the west, for her bird-loving father. "From the main bedroom, you look right into the treetops," she says. The voluminous central conservatory was for her plant-loving mother, who grows orchids, cymbidiums, aerophytes and all nature of green delights.

This barn-like volume is at the very centre of the home. The heart of many traditional South African homes - like the Karroo cottage Engelbrecht's mother showed her - is a covered front patio or stoep. The long, warm summers and mild winters make indoor-outdoor living a foregone conclusion.

"My mom wanted a closed stoep so she could have soft furnishings - and also for the stoep not to be a room next to the house, but in the house," says Engelbrecht. "So, this is the core of the house - our conservatory."

An automated opener lifts up one of the glass walls so that it disappears entirely, meeting the vastness of the view with a voluminous interior. To one side is a kitchen and an informal seating area cum TV room. To the other, a lounge, his-and-hers glassed-in office spaces, and a bedroom.

Below, visible through a strip of glass floor near the entrance, is a wine cellar.

"Believe it or not, this is really just a one-bedroom house," says Engelbrecht.

Well, that's not quite true. Downstairs, tucked into the hillside, is a self-contained guest suite for visiting family and friends: "two bedrooms and bathrooms, and a shared little kitchenette and lounge area" as Engelbrecht describes it.

Close to her heart is the notion of passive design, sustainability and energy efficiency. "In South Africa, because of the climate, if you design a house well, you don't need alternative heating and cooling," she says.

The farm has three dams, which take care of its water supply, and she incorporated 16 photovoltaic panels on the roof to cover most of the power requirements. "Everything but the oven," says Engelbrecht.

It's also carefully insulated. "Our overhangs are correct, so in winter sun comes into the house," she says. With the doors closed, it's lovely and warm. "In summer, if you keep the doors open, it cools naturally. It's never too hot. When everything is open, it breathes, and its temperature stays constant."

As well as being a plant-lover, Charmaine is a champion of local art and design. She frequents student exhibitions, buying the works of upcoming artists to support them. Almost all the furnishings in the house are by local designers. The spectacular timber chandelier above the dining table in the conservatory is by David Krynauw. In the lounge, there's a bench by Laurie Wiid van Heerden, a table by Gregor Jenkin, and Ronel Jordaan chairs.

The dining table was designed by Nadine and made by Andre, a keen amateur carpenter who also contributed to the timberwork in various spaces, such as the custom-made steel kitchen island. The dining chairs - originally classroom chairs - came from an antique shop. The workbench in the conservatory was salvaged from the original farmhouse.

It's an eclectic mix that is beautifully resolved in the simple palette of white walls, timber, concrete and steel carried throughout the interiors. The landscaping was largely a matter of rehabilitating the natural grassland around the house, introducing waterwise varieties on the inclines where heavy rain would have washed out the grass.

"We've got some lawn for the dogs and kids to play," says Engelbrecht. "Otherwise, everything is endemic."

And with that massive, light-filled volume at its centre, filled with plants and greenery, the landscape seems to fill its green heart too. Simplicity itself. - Bureaux