Snow Load Safety Guide: Risk Management Series

The objective of the Risk Management Series Snow Load Safety Guide is to inform building stakeholders about the risks a snow event poses to their buildings, provide them with information about preventative measures to take before the snow season, and inform them of actions that should be taken before, during, and after a snow event. 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. Structural failure due to roof snow loads may be linked to several possible causes, including but not limited to the following: Actual snow load significantly exceeds design snow load; Drifting and sliding snow conditions; Deficient workmanship; Insufficient operation and maintenance; Improper design; Inadequate drainage design; Insufficient design; in older buildings, insufficient design is often related to inadequate snow load design criteria in the building code in effect when the building was designed. This document is not intended to provide a comprehensive discussion of the underlying issues or forensics of snow-induced structural failure. The purpose is instead to: Inform building stakeholders of susceptible snow loading conditions; Identify potentially vulnerable roof framing systems; Outline a general methodology to monitor buildings for signs of potential failure so that steps can be taken to reduce the potential risk of snow-load-induced structural failure. FEMA P-957.