The importance of internal gutter dimensioning in large rooftops

Abstract

Rainfall intensities and intensity x frequency x duration (IFD) values have varied due to increasing climate change. It is observed that, even in regions with apparently stable or even low rainfall, there has been rainfall with atypical IFDs never seen before. Thus, in this study, we sought to describe the dimensioning of the Siphonic Stormwater Drainage System of the internal gutters of large roofs and their emergency drainage to identify the associated impacts. It was observed that the European standards describe in detail the design of internal gutters, including the most used, rectangular box gutters. The bibliographical research carried out provided the parameters that support the design of internal gutters. NBR 10844:1989 provides rainfall values for a return period T=25 years, while for internal gutters EN 12056-3:2000 and DIN 1986-100:2008 require the use of a return period of T=100 years. A design exercise was carried out for the design of internal gutters as described in EN 12056-3:2000, DIN 1986-100:2008 and the literature consulted, allowing to highlight: i) the use of safety factors; ii) rainfall values with a return time of 100 years; iii) internal gutters must be dimensioned with a freeboard, and iv) internal gutters must-have emergency drainage. Many commercial and industrial developments have internal gutters not dimensioned according to international standards without emergency drainage. Failures produce overflows, and material damage to buildings is the consequence.