A central stringer staircase is a special type of space-saving staircase in which the steps are mounted on support elements along the centre line of the staircase. The support elements are made of metal and are adjustable in height, which means that central stringer stairs are considered very flexible and space-saving. Central stringer staircases are sometimes also called mono-stringer staircases.
The term clear room height refers to the distance from the upper edge of the floor to the lower edge of the ceiling. The clear room height is particularly relevant when purchasing attic stairs.