The Ontario Building Code | Specified Snow Loads
9.4.2.2. Specified Snow Loads
(1) Except as provided in Sentences (2) and (3), specified snow loads shall be not less than those calculated using the following formula:
S = Cb ∙ Ss+ Sr
where,
S = specified snow load,
Cb = basic snow load roof factor, which is 0.45 where the entire width of a roof does not exceed 4.3 m and 0.55 for all other roofs,
Ss = 1-in-50 year ground snow load in kPa, determined according to MMAH Supplementary Standard SB-1, "Climatic and Seismic Data", and
Sr = associated 1-in-50 year rain load in kPa, determined according to MMAH Supplementary Standard SB-1, "Climatic and Seismic Data".
(2) In no case shall the specified snow load be less than 1 kPa.
(3) Bow string, arch or semi-circular roof trusses having an unsupported span greater than 6 m shall be designed in conformance with the snow load requirements in Subsection 4.1.6.