Roof Design: Avoid Ponding by Sloping to Drain

by Gary Van Ryzin, Proj. Mgr.; National Roofing Contractors Assoc., Oak Park, Ill.,

Serial Information: Civil Engineering—ASCE, 1980, Vol. 50, Issue 1, Pg. 77-81

Document Type: Feature article


Roofing contractors recommend that roofs possess enough slope to permit complete drainage within 48 hours of rainfall. Otherwise ponds will form which can cause leakage and even contribute to roof collapse. Although this advice has been around for a long time, few have followed it because it involves added expense. Article discusses the hazards of ponding water and how they may be prevented either by designing adequate slope into the original roof or adding it later. Case histories describe typical leakage problems and a case of structural failure.

Subject Headings: Case studies | Roofs | Slopes | Drainage | Leakage | Structural failures | Contractors and subcontractors | Permits

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