Abstract: The present staircase includes a permanent framing made of metallic stringers, one of which being typically secured to a half-timbering. Vertically extending step supports are secured along the stringers and each include upper and front flanges adapted to be secured respectively to a tread and to a riser of each step of the staircase. A temporary staircase may be easily obtained with the present kit for use during construction, wherein a number of L-shaped steel step units are laid onto the step supports to form a successive series of alternating risers and treads. Then, these L-shaped steel units can be removed and replaced by finished steps of various configurations. If the staircase has an exposed side, a finishing stringer is provided thereat to conceal the structural metallic stringer.