Many areas have been hit with freezing rain today and even though it has generally not been enough to warrant concern for the structures, it is a good time to recap some common things when dealing with ice on buildings.
It is important to note that the ice in itself is not an issue, even a very thick layer actually has enough strength to become self supporting. There are two potential problems though:
If the ice stays on the building, it usually has a rough enough texture that subsequent snow will not likely slide off. This scenario lead to major problems in previous winters when we had freezing rain, followed by a dump of snow and then we had rain. This can triple the weight on a building in very short order.
The other potential problem happens when you are attempting to remove the ice from the building. If the ice layer is not too significant you can gently bump the cover from the inside. ALWAYS start bumping the cover from the top. This way ice will slide over ice. Starting from the bottom creates a potential where the ice sliding down will fall back against the building and slash the cover. NEVER do all of one side and then the other. Work both sides simultaneously.
If there is the slightest doubt in your mind about the amount of weight on the building, bump the cover from the outside using something with a long handle.