S-2.1, r. 4 - Safety Code for the construction industry
3.6.1. Any building under construction shall be provided with 2 means of egress by means of permanent or temporary stairs which shall:
(a) be built for the entire height from the ground or underground to the working level as soon as the work has attained a height of 2 storeys or 6 m above ground;
(b) be extended as work progresses without adversely affecting construction work;
(c) never be extended at less than 2 storeys from the upper working level; and
(d) be built of steps with a depth more than 150 mm.
R.R.Q., 1981, c. S-2.1, r. 6, s. 3.6.1.