The ground floor of the 30-square-metre shed is used to store gardening tools, but a brass hatch in the ceiling leads up to the light-filled upper space.
Called The Enchanted Shed, it is mainly used as a writing studio, but can also host guests or function as a playroom.
"The special appeal of this project lay in the rediscovery of these old outbuildings in the shadows of the Vienna Woods villas," said the architects.
"Back in the 1930s, few people could afford a basement, let alone a garage," they continued. "And so they built their own sheds to store wood, raise rabbits or boil laundry, which was then hung up to dry in the attic."
"Over the past few decades these structures have lost their original purpose, and many are falling apart. This is a real pity."
Upstairs, one gable is entirely glazed to permit views into the treetops, while an upholstered seat that doubles as a bed is integrated into the opposite end of the space.
"Spotlights illuminate the brass in the evening, creating a warm light – even in freezing winter, when the unheated room is used for cooling down after a sauna session," explained the architects.
The ceiling and walls are panelled in varnished grey fir, while the floorboards are a more warm-toned wood.
Downstairs, double doors give the owners easy access to gardening tools, their lawnmower and fruit crates.
The prevalence of garden studios is increasing as real-estate prices spike.
New York's Brooklyn is one of the hotspots for this typology – the area has seen a flurry of shed-like studio spaces appear as residents look to maximise limited space.
Photography is by Andreas Buchberger.
Architecture: Sue Architekten
Project team: Christian Ambos, Michael Anhammer, Harald Höller
Collaborator: Anna Ladurner