(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.
(2) Sealing or drainage are not required where it can be shown that the omission of sealing and drainage will not adversely affect any of,
(a) the health or safety of building users,
(b) the intended use of the building, or
(c) the operation of building services.