(See Note A-9.8.4.7.)
(1)
Spiral stairs shall have
(a)
handrails on both sides, the outer handrail being not less than 1 070 mm high,
(b)
a clear width not less than 660 mm between handrails,
(c)
risers that are not more than 240 mm high,
(d)
treads that
(i)
are a minimum of 190 mm deep at a point 300 mm from the centre line of the handrails at the narrower edge,
(ii)
have a consistent angle and uniform dimension, and
(iii)
turn in the same direction, and
(e)
not less than 1 980 mm clear height.
(2)
Spiral stairs conforming to Sentence (1) are permitted to be used as the only means of egress where they serve not more than 3 persons.
(3)
Except as permitted by Sentence (2), spiral stairs shall not serve as an exit.