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1503.4 Roof drainage. <br />Design and installation of roof drainage systems shall comply with Minnesota Rules, Chapter 4715, Minnesota Plumbing Code, and the following <br />provisions: <br />1. Where required. <br />All roofs shall drain into a separate storm sewer system or to an approved place of disposal. For one- and two-family dwellings, and where approved, <br />storm water is permitted to discharge onto flat areas, such as streets or lawns, provided that the storm water flows away from the building. <br />2. Roof design. <br />Roofs shall be designed for the maximum possible depth of water that will pond thereon as determined by the relative levels of roof deck and overflow <br />weirs, scuppers, edges, or serviceable drains in combination with the deflected structural elements. In determining the maximum possible depth of water, <br />all primary roof drainage means shall be assumed to be blocked. <br />3. Secondary drainage required. <br />Secondary (emergency) roof drains or scuppers shall be provided where the roof perimeter construction extends above the roof in such a manner that <br />water will be entrapped if the primary drains allow buildup for any reason. <br />4. Separate systems required. <br />Secondary (emergency) roof drain systems shall have piping and point of discharge separate from the primary system. Discharge shall be above grade in <br />a location which would normally be observed by the building occupants or maintenance personnel. <br />5. Sizing of secondary drains. <br />Secondary (emergency) roof drain systems shall be sized in accordance with the Minnesota State Plumbing Code. Scuppers shall be sized to prevent the <br />depth of ponding water from exceeding that for which the roof was designed as determined by this code. Scuppers shall not have an opening dimension of <br />less than 4 inches (102 mm). The flow through the primary system shall not be considered when sizing the secondary roof drainage system. <br />[P] 1503.4.1 Secondary (emergency overflow) drains or scuppers. <br />Deleted. <br />Deleted <br />1503.4.2 Scuppers. <br />When scuppers are used for secondary (emergency overflow) roof drainage, the quantity, size, location and inlet elevation of the scuppers shall be sized <br />to prevent the depth of ponding water from exceeding that for which the roof was designed as determined by Section 1611.1. Scuppers shall not have an <br />opening dimension of less than 4 inches (102 mm). The flow through the primary system shall not be considered when locating and sizing scuppers. <br />1503.4.3 Gutters. <br />Gutters and leaders placed on the outside of buildings, other than Group R-3, private garages and buildings of Type V construction, shall be of <br />noncombustible material or a minimum of Schedule 40 plastic pipe.