FEMA P-957 Risk Management Series: Snow Load Safety Guide  

Most buildings are not at risk of snow induced failure. More often than not, attempting to remove snow from a roof is more hazardous than beneficial, posing a risk to both personnel and the roofing structure. However, snow accumulation in excess of building design conditions can result in more than a temporary loss of electrical power and inaccessible roads. Buildings may be vulnerable to structural failure and possible collapse if basic preventative steps are not taken in advance of a snow event. Knowledge of the building roof framing system and proper preparation in advance of a snow event is instrumental in reducing risk to the structure.