Lloyd Alter is Design Editor for Treehugger and teaches Sustainable Design at Ryerson University in Toronto. Alternating tread stairs are terrific for saving space; you only put one foot on a tread at ...

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 ...

You may be like most folks. I’m guessing you give very little thought to the stairs you go up and down on a regular basis. They might be constructed from wood, steel, or concrete. The vast majority of ...