Ponding

In civil engineering, ponding is the (typically) unwanted pooling of water, typically on a flat roof or roadway. Ponding water accelerates the deterioration of many materials, including seam adhesives in single-ply roof systems, steel equipment supports, and particularly roofing asphalt. On low-slope asphalt roofs, ponding water allows the oil solvent components of the asphalt to leach out and evaporate, leaving the roof membrane brittle and susceptible to cracking and leaking in the ponding location.[1] The time taken for water to saturate a zone, usually from rainfall, causing a pond to form, is referred to as the "ponding time" 

book|url=https://books.google.com/books?id=QKJdsJ0tkt8C&dq=%22time+of+ponding%22&pg=PA98%7Ctitle=Infiltration Theory for Hydrologic Applications|publisher=American Geophysical Union|language=en}}</ref>[2][3]
  1. ^ "Building Envelope Design Guide - Roofing Systems | Whole Building Design Guide". www.wbdg.org. Retrieved 2016-08-11.
  2. ^ Brutsaert, Wilfried (2005-08-11). Hydrology: An Introduction. Cambridge University Press. ISBN 978-0-521-82479-8.
  3. ^ Delleur, Jacques W. (2010-12-12). The Handbook of Groundwater Engineering. CRC Press. ISBN 978-1-4200-4858-2.