Double Quarter-Turn Stair (two 90° turns) — Layout variation
Category: Layout variation
Continuous flight with two 90° changes of direction — standard U- or Z-shape.
In a double quarter-turn stair the flight direction changes twice by 90° each – usually once at the bottom and once at the top. The curving at the beginning and end creates a U-shaped plan layout with no intermediate landing, which keeps the walking motion continuously flowing. This form is particularly useful when the bottom and top of the stair need to be spatially offset while avoiding a break by a landing. The steps in the curved sections are executed as winder treads whose goings are flared to maintain a uniform going along the walking line.
Related terms
Related terms: Quarter-Turn, Single Quarter-Turn Stair (one 90° turn), Half-Turn Stair, U-Shaped Stair.