This half-scale model of a spiral staircase by American studio Matter Design is made from concrete treads that slip neatly over each other. Above and top: photograph by Brandon Clifford The Helix ...

A popular look is the rust-resistant aluminum spiral staircase that is powder coated and available in white, black or custom colors. A variety of tread styles, handrails and balusters are available.

birch plywood treads that are progressively attached around the tree trunk with ratchet straps, so that the stairs can spiral up into the leafy canopy. Rubberized treads, and a railing made out of ...

If we try 15 steps, we will have 27 cm treads and 20 cm risers. Applying the Blondel law, we end up with a total of 67, which would slightly exceed a conventional staircase. In a spiral staircase ...