The Ontario Building Code | Sealing and Drainage
220.127.116.11. Sealing and drainage
(1) Except as provided in Sentence (2), materials, components, assemblies, joints in materials, junctions between components and junctions between assemblies exposed to precipitation shall be,
(a) sealed to prevent ingress of precipitation, or
(b) drained to direct precipitation to the exterior.
(a) the health or safety of building users,
(b) the intended use of the building, or
(c) the operation of building services.