(1)
Flights of stairs shall consist solely of
(a)
straight flights, or
(b)
curved flights complying with Sentence (2).
(2)
Tapered treads in a curved flight that is not required as an exit shall have
(a)
a minimum run of 150 mm,
(b)
a run not less than 280 mm when measured at a point 300 mm from the centre line of the handrail at the narrow end of the tread, and
(c)
a riser conforming to Sentence 3.4.6.8.(2).
(3)
Tapered treads shall have a consistent angle and uniform run and rise dimensions in accordance with the construction tolerances described in Article 3.4.6.8. when measured at a point 300 mm from the centre line of the handrail at the narrow end of the tread.
(4)
All tapered treads within a flight shall turn in the same direction.