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Roof Snow Load Advisory - 1/27/2011

Guidance from the Rockland County Office of Fire and Emergency Services

Guidance from the Rockland County Office of Fire and Emergency Services





Heavy snows combined with extremely cold weather conditions provide a cause for concern about the potential for roofing failures due to an extraordinary accumulation of snow and ice.  Although a roofing failure due to accumulated ice and snow loads is rare, there are several roof types and conditions, which you should be particularly mindful of, including:


Low sloped roofs:  Low slope or “flat” roof construction (i.e., roofs with less than ˝ inch per foot slope) should be checked to determine if significant ice/snow accumulations exist.  Ideally roof drains should be free flowing, and not frozen or clogged with debris, to allow melted water to be removed from the roof.  Evidence of significant water leakage internal to buildings, deflection (sagging) of structural members or any movement in exterior walls or parapets should be considered as signs of a potential roof failure.


Light frame construction and minor roofs:  Typically smaller commercial and utility buildings (usually less than 10,000 square feet) with low sloped roofs, and light weight bar joist or wood truss roof structural support systems should be checked to be certain that structural integrity is being maintained.  Again, evidence of significant water leakage or any movement in structural supports or exterior walls/parapets should be noted and appropriate measures taken.  Minor roofs such as canopies over building entries, small storage sheds or shelters, which may also have lighter structural support systems, should be examined.


Agricultural buildings:  Agricultural buildings including barns, agricultural storage facilities and similar structures should be checked for significant snow/ice accumulations.  Again roofs with lighter weight structural support systems or buildings showing evidence of any structural damage should be addressed.


Drifted Snow Accumulations:  High winds associated with the recent snow storm, especially in the lower Hudson Valley and New York Metropolitan area, may have caused significant drifting of snow on roof surfaces.  Large snowdrifts can add significant loading to portions of any roof and can contribute to roofing failures.  This is especially true of large flat roof structures such as commercial warehouse, factory, arenas or large retail structures where snowdrifts can occur over larger areas of the roof and where mechanical equipment or other roof top structures allow drifts to readily form.  Smaller pitched roof surfaces can also exhibit significant accumulations due to drifting in valleys and areas where sloped roof surfaces come together.


Safe Removal of Accumulated Snow and Ice:  Excess snow and ice accumulations can be safely removed from roofs.  In most cases, however, only experienced and qualified roofing contractors should only undertake this work.  Private property owners, including homeowners, should not be encouraged to remove snow and ice accumulations from roof surfaces.  Snow rakes can be safely used to remove snow from residential roofs from the ground; however, contact with power lines is a serious concern.  Anyone who is not certain of safe roof snow and ice removal practices should contact a qualified roofing contractor.


Parking Decks/Garages:  During the month of February 2007, two parking garages in our area experienced a section of the parking deck collapsing due to excessive snow load.  The primary cause of the collapse was snow being plowed into one area of the parking deck and the weight of the snow exceeded the design load of the structure.  Should you plan to store plowed snow on the parking deck, then you should contact your local building/fire code official for guidance to ensure you do not exceed the design load of your structure.





G:Safety Winter Tips/Roof Snow Roof Advisory


Town of Clarkstown 10 Maple Avenue, New City, NY 10956 (845) 639-2000
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