Demystifying Gutter and Downspout Sizing


Why is it that while gutters and downspouts are common components on the majority of all residential and commercial buildings with steep slope roofs, architects and builders seem to fail to go through the process of designing this important storm water drainage element and leave them un-sized or incorrectly sized? Perhaps it is because they ‘straddle the fence’ of architectural and plumbing components. While their design documentation is shown on architectural drawings and in specifications, their design requirements are found in the Plumbing Code, which is maintained and updated separately. In 2015, the International Plumbing Code was updated to reflect new knowledge on storm drainage providing the correct sizing of gutters and downspouts as well as new Code requirements.  With AGS online, we can help you to manage both architectural and plumbing components by providing up-to-date information on code requirements and calculations as well as architectural specifications.

Since 1932, Architectural Graphic Standards (AGS) has sought to provide architects with the most current design practices and standards. With the power of electronic online publishing, AGS Online is able to continuously update technical and design knowledge in an industry that can’t wait on traditional book publishing. “Gutters and Downspouts: Sizing Calculations” is the first of the AGS Online series and reflects the current standard of care in building design for this subject. It includes a step-by-step design process, ICC table and figures, and a sample design problem and solution.

Current subscribers, check out the latest update to AGS online,Gutters and Downspouts: Sizing Calculations.”

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Dennis J. Hall, FAIA, FCSI