In the Netherlands drug addicts are provided with controlled heroin by the authorities. A temporarily building that could be used for ten years was chosen in order to relocate one such care institution. The programe of care provision and associated offices was translated onto a modular, 6 x 3 metres grid. The building was quickly assembled on site and the outside was then finished with wooden cladding. This conceals all signs of the building’s modular production and gives it permanence.