The Ontario Building Code | Accumulation and Disposal
22.214.171.124. Accumulation and Disposal
(2) Where precipitation can accumulate on sloped or horizontal assemblies, provision shall be made for drainage conforming with Section 7.4.
(3) Where downspouts are provided and are not connected to a sewer, provisions shall be made to,
(a) divert the water from the building, and
(b) prevent soilerosion.
(4) Junctions between vertical assemblies, and sloped or horizontal assemblies, shall be designed and constructed to minimize the flow of water from the sloped or horizontal assembly onto the vertical assembly.