Images Lara Calder via Archdaily
Buildings don't have to just sit on the ground; Australian architect Lara Calder's Parasite Prefabs just grow wherever they can get away with it, on the sides of bridges, rock faces or old buildings. Designboom says "It finds value by turning dead public space into lively private space."
Just bolt a back plate onto the surface when nobody is looking and then quickly assemble the prefab components. The staircase is retractable, pulled up like a drawbridge, having a footprint that "technically only consists of the stair landing and the services duct."
One the first level, the building contains the main entrance and the study. The bedroom and bathroom are on the second level and the main room has access to a balcony which is protected by a privacy screen. The upper floors contain the living space, kitchen, and small roof terrace, which provides the opportunity for natural cross ventilation.