Spiral staircases are perfect where space is a premium due to their relatively small & efficient footprint and can be designed in a variety of styles.
They are suitable for both indoor and outdoor use and the most common formats are circular with a central mast and fixed screw-format steps. The structure is build in metal whilst the steps can be in glass, wood or steel with or without railing depending on the enclosing wall.
With regards to finishes for outdoors we recommend galvanized which is a protective zinc coating that is applied to steel/ iron in order to prevent premature rust & corrosion. Otherwise powder coating is used to create a hard tough finish that is stronger than conventional paint. Any colour could be used.