The Ontario Building Code | Purpose of Roofing
9.26.1.1. Purpose of Roofing
(1) Roofs shall be protected with roofing, including flashing, installed to shed rain effectively and prevent water from entering the roof as a result of ice damming.
(2) For the purpose of Sentence (1), roofs shall include platforms that effectively serve as roofs with respect to accumulation or drainage of precipitation.