Editing Snow (section)

====Roofs====
[[File:Ice dam and roof leakage.jpg|thumb|right|Icings resulting from meltwater at the bottom of the snow pack on the roof, flowing and refreezing at the eave as icicles and from leaking into the wall via an ice dam.]]
Snow loads and icings are two principal issues for roofs. Snow loads are related to the climate in which a structure is sited. Icings are usually a result of the building or structure generating heat that melts the snow that is on it.

''Snow loads'' – The ''Minimum Design Loads for Buildings and Other Structures'' gives guidance on how to translate the following factors into roof snow loads:<ref name = ASCE7/>
* Ground snow loads
* Exposure of the roof
* Thermal properties of the roof
* Shape of the roof
* Drifting
* Importance of the building
It gives tables for ground snow loads by region and a methodology for computing ground snow loads that may vary with elevation from nearby, measured values. The ''Eurocode 1'' uses similar methodologies, starting with ground snow loads that are tabulated for portions of Europe.<ref name=Eurocode1/>

''Icings'' – Roofs must also be designed to avoid [[Ice dam (roof)|ice dams]], which result from meltwater running under the snow on the roof and freezing at the eave. Ice dams on roofs form when accumulated snow on a sloping roof melts and flows down the roof, under the insulating blanket of snow, until it reaches below freezing temperature air, typically at the [[eaves]]. When the meltwater reaches the freezing air, ice accumulates, forming a dam, and snow that melts later cannot drain properly through the dam.<ref name="Paul" >Paul Fisette, "Preventing Ice Dams", ''Roofing, flashing & waterproofing''. Newtown, CT: Taunton Press, 2005. 54.</ref> Ice dams may result in [[Water damage|damaged]] building materials or in damage or injury when the ice dam falls off or from attempts to remove ice dams. The melting results from heat passing through the roof under the highly insulating layer of snow.<ref>{{citation| url=http://www.state.mn.us/portal/mn/jsp/content.do?test=y&id=-536881350&subchannel=-536881511&sc2=null&sc3=null&contentid=536884951&contenttype=EDITORIAL&programid=536886479&agency=Commerce|title=Ice Dams|publisher=Minnesota Department of Commerce|archive-url=https://web.archive.org/web/20070824154322/http://www.state.mn.us/portal/mn/jsp/content.do?test=y&id=-536881350&subchannel=-536881511&sc2=null&sc3=null&contentid=536884951&contenttype=EDITORIAL&programid=536886479&agency=Commerce| archive-date=August 24, 2007}}</ref><ref name="Hansen" >
{{Citation
 | first1 = I.
 | last1 = MacKinley
 | first2 = R.
 | last2 = Flood
 | first3 = A.
 | last3 = Heidrich
 | editor-last = Hjorth-Hansen
 | editor-first = E.
 | editor2-last = Holand
 | editor2-first = I.
 | editor3-last = Loset
 | editor3-first = S.
 | editor4-last = Norem
 | editor4-first = H.
 | contribution = Roof design in regions of snow and cold
 | isbn = 9789058091482
 | title = Snow Engineering 2000: Recent Advances and Developments
 | year = 2000
 | pages = 470
 | place = Rotterdam
 | publisher = CRC Press
 | url = https://books.google.com/books?id=EjGsPSoYHOIC
}}</ref>