For the spiral staircases: at least 5 cm more than the diameter of the staircase for comfortable gripping of the handrail. For the winder staircases: the opening in the floor should be at least the dimensions of the staircase less two treads.

For the winder staircases, the answer is yes. For the spiral staircases, you can do so, but with some restrictions.

The components of the Steel Zink model are treated in a molten zinc bath, which is the best protection against rust. Technically, it consists of a sequence of operations such as pickling, a zinc bath and an antioxidant protective primer. This treatment may cause some imperfections, which however do not compromise the high quality of the product supplied.

The imperfections you may find on the Steel Zink model can be eliminated with a file, covering the cold-zinc treated parts contained in the crate.

The diameter of the central pole of Pixima Ring and Cube is:
10.8 cm for the diameters 118, 128 and 138.
12.7 cm for the diameters 148 and 158.

You will find the useful width of the staircase in the attached PDF file..

The dimensions of the Pixima landings are indicated in the product catalogues for each configuration. The PDF files of the catalogues can be downloaded from the Download section.

The base plate diameter is 21 cm for all the staircase diameters. The outside diameter of the plate cover is 24 cm.

No, they cannot be turned the other way round, but they can be turned upside down.

No. For the Cube staircase the railing is supplied on request as the number of balusters strictly depends on the configuration of the walls around the staircase.