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CROSS Safety Report

Snow sliding off industrial building roofs

Report ID: 438 Published: 1 October 2014 Region: CROSS-UK

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Overview

A lean-to roof at lower level than the main roof of a large industrial building collapsed and ground level equipment was damaged due to a sliding snow.

Key Learning Outcomes

For civil and structural design engineers:

  • Careful consideration should be given to the risk of sliding snow. In particular, for areas prone to heavier snow falls and if the roofs coverings are of glass or other slippery material where snow can accumulate and then slide as an entire mass

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Collapse of a lean-to roof, at a lower level than the main roof of a large industrial building, and damage to ground level equipment, was caused by snow. It had accumulated on the main roof, thawed and slid off imposing large imposed loads due to impact.

The reporter says that sliding snow forces are addressed in UK codes but only in the context of loads on the back of parapets. Modern single storey buildings can have shallow curved roof profiles and no parapets so there is little restraint to snow falls from height.

Sliding snow falling from eaves is acknowledged abroad, typically on relatively steep roofs by the use of snow guards at eave positions. Some projects in the UK incorporate snow guarding but the risk of snow falling through height is generally not considered. Building designers should assess the risk to users and adjacent structures of snow load impact resulting from large roofs with no parapets.

Expert Panel Comments

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This eventuality requires more publicity, and the report is an example of how design should be risk based rather than code-driven. Indeed, designers should address this risk especially in areas prone to heavier snow falls and if the roofs coverings are of glass or other slippery material where snow can accumulate and then slide as an entire mass.

In cold parts of Europe (and elsewhere) pedestrians have been killed by large icicles. In any risk assessment the generic hazard of ‘falling objects’ should be one of the key words.  CROSS has previously had reports on collapses due to snow loads. You can search for safety information on snow loads on the CROSS website.

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