Accumulating wet snow or wet snow coupled with sleet and/or rain can present a threat of roof collapse (as well as aggravate localized basement flooding, particularly when street drains are not shoveled clear).
If not cleared off of roofs, snow can absorb additional sleet and rain, increasing roof loads and adding stress to building structures.
Relatively flat roofs are particularly vulnerable. Additionally roof ice dams can form on any roof, causing water build-up which can lead to interior water damage. To minimize the risk of over-stressing a building roof due to accumulated or drifting snow:
- Be on the alert for large accumulating snow build-up or snowdrifts on your roofs.
- If roof snow can be removed with the use of a snow rake (available at most hardware stores), do so. Use caution, as metal snow rakes conduct electricity if they come into contact with a power line.
- Try to avoid working from ladders, as ladder rungs tend to ice up. Snow and ice can also collect on boot soles, and metal ladders making the climbing of ladders dangerous in winter months.
- Flat roofs can be shoveled clear, but only if it is determined that the roof is safe to stand upon. Exercise care when on the roof to avoid potentially dangerous falls.
- Flat roof drainage systems should be kept clear to minimize the risk of excess roof ponding in the event of subsequent heavy rainfall or melting.
- Large icicles can form on roof overhangs, but do not necessarily mean ice damming is occurring. Icicles overhanging doorways and walkways can be dangerous as potential falling objects and should be carefully removed.
- All of the mentioned actions should only be performed by able-bodied adults, as snow can be heavy, and roofs and other surfaces may be slippery. Protective headgear and eye protection is recommended.