The Ontario Building Code | Access
(a) measures not less than,
(i) 10 m² in area,
(ii) 1 000 mm in length or width, and
(iii) 600 mm in height over at least the area described in Subclauses (i) and (ii), or
(b) contains a fuel-fired appliance.
(2) Except where an attic or roof space contains a fuel-fired appliance, the hatch required in Sentence (1) shall be not less than 550 mm by 900 mm except that, where the hatch serves a single dwelling unit, the hatch may be reduced to,
Note: On July 1, 2017, Sentence 184.108.40.206.(9) of Division B of the Regulation is amended by striking out "single dwelling unit" in the portion before Clause (a) and substituting "house or an individual dwelling unit in a house". (See: O. Reg. 139/17, s. 122)
(a) 0.32 m2 in area with no dimension less than 545 mm, or
(b) 500 mm by 700 mm.