Arbloc has introduced computer design in the production of formworks for stairs. This allows us to be precise in the development of 3D shapes based on drawings, the same result would be diffi cult to achieve with traditional wood carpentry. From the 3D model, we move to the processing of polystyrene foam using numerically controlled cutters and faithfully respecting the geometries. The resulting a formwork allows the company to obtain a uniform concrete casting on the steps and the helical plane