Guidance from the Rockland County Office of Fire and
ROOF SNOW LOAD ADVISORY
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.
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.
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
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