Alternating tread staircase
An alternating tread staircase or staggered step staircase is a staircase with L-shaped steps, allowing the user to ascend or descend by alternating steps. It saves space and allows for a steeper slope while maintaining comfortable step depth.
Angle
Determines the slope of the staircase. The angle must be between 20 and 50°. Its ideal value is 30°.
Balancing
A balanced staircase is a staircase where the steps gradually turn at the angles. Mainly used in Europe, balancing improves comfort, safety, and aesthetics of a staircase. Balancing also increases the contact surface with the interior stringer.
Blondel's law
G + 2H = 590 to 650mm (23.2 to 25.6") Formula invented by French architect François Blondel (1618-1686) verifying the consistency between step height and going. The ideal value is 630mm (24.8").
Flight
Series of steps between 2 landings.
Floor opening
Opening in the upper floor allowing the passage of the staircase.
Going
Horizontal distance between two step nosings. The going must be between 230 and 330mm (9 and 13"). Its ideal value is 280mm (11").
Half-turn staircase
A half-turn staircase or double quarter-turn staircase is a staircase consisting of 2 90° angles.
Headroom
Distance between the ceiling and the walkline at the floor opening. The headroom must be greater than 1900mm (75") and its ideal value is greater than or equal to 2100mm (83").
Height
Vertical distance between the lower floor and the upper floor.
Landing
Horizontal surface wider than the usual steps. It allows for a rest or a change in the direction of the staircase.
Landing step
Step in the extension of the upper floor. It provides an overlap on the last step. It also facilitates the connection of the stringer and the handrail with the upper floor.
Overlap
Part of the step covered by the step above. The overlap helps improve the comfort of the staircase.
Quarter-turn staircase
A quarter-turn staircase is a staircase consisting of a 90° angle.
Riser
Vertical part connecting 2 consecutive steps.
Spiral staircase
A spiral staircase or helical staircase is a staircase where the steps radiate around a central axis.
Stair width
Usable width of the staircase. The stair width must be greater than 700mm (28") and its ideal value is greater than or equal to 800mm (32").
Step
Horizontal surface on which the foot is placed.
Step height
Vertical distance between two step nosings. The step height must be between 150 and 200mm (6 and 8"). Its ideal value is 175mm (7").
Step nosing
Overhanging part of a step.
Straight staircase
A straight staircase is a staircase without a change in direction.
Stringer
Element that holds the staircase steps.
Total run
Horizontal distance between the nosing of the first step and the step nosing of the upper floor.
Walkline
Fictitious line symbolizing the user's path. It determines the going for turning staircases. If the stair width is less than or equal to 1m (40''), the walkline is located in the middle. If the stair width is greater than 1m (40''), the walkline is located 500mm (20'') from the interior handrail.