This project was born as a challenge with a friend/client, design a cabin with a max 50 sq mt surface a cost of 1200 €/sq mt and able to accommodate 4 person. The main structure, a steel cage, without pillars in order to permit the maximum flexibility in distribution. The walls are of steel stud and plasterboard construction, with two external plasterboard layers and a timber coating in interior faces. Main structure is made using 200x200 mm metal steel square tubes and the secondary with 100x100 mm square tubes. The basement, the wall and the ceiling are made with SIPs (Structural Isulated Panel system) 100 mm thick; with isulated foam in the interior. External face is realized with an outdoor plasterboard panel 13 mm thick, waterfroof finished; between this element and the sips panel there is a breather membrane that run all around the house. The roof is finished with a galvanized iron sheet flashing and a wooden grid that allow to use the roof as a terrace. This elements may be raplaced with solar panel, in order to allow energy efficiency in isolated contexts.