Snow on the Roof vs Ice on the Roof Snow on the Roof vs Ice on the Roof
The accumulation of snow and ice on a roof can have serious consequences for a homeowner who lives in a climate where heavy snowfall and extreme low temperatures are commonplace. Although both snow and ice can damage a roof, they are different in the way they accumulate and the type of damage they are prone to cause. To say that one is better to have on the roof than the other is not entirely true, for given the right circumstances they both can damage the roof structure. Snow or ice on the roof is similar in that both add excess weight that could be problematic. However, each poses their own unique set of problems.
Snow on the Roof
The term used to describe the downward force of snow upon a structure is snow loading. This very real concept is especially important in regions that see tremendous amounts of annual snowfall. The roof of a structure is most vulnerable to snow loading, for it bears the brunt of the weight. Certain factors can make a roof more susceptible to damage caused by snow loading. These include improper re-roofing, faulty measures to protect the structure and insulating the roof without providing for air ventilation. Old roofs are even more at risk due to their age and possibly inept structure.
The pitch of the roof and the drift of the snow can also affect snow loading. A-frame roofs are designed to prevent hardly any snow from building up, whereas flatter roofs do not have this luxury. A cubic foot of snow can weigh between 7 and 30 pounds depending on how new it is and if it has compacted or if rain has fallen on top of it.
Ice on the Roof
The biggest danger with the accumulation of ice on the roof is the formation of ice dams. Ice dams form at the eaves or overhangs of roofs. As snow melts and refreezes it creates hanging icicles. Enough of it will create large ice barriers just behind these lovely hanging ice formations. Any snow trapped behind it has nowhere to go when it melts, so it pushes up into and underneath the shingles. This can rot shingles, felt, wood sheathing and the interior of the crawl space. The best way to avoid the buildup of ice dams is to have a properly ventilated crawl space.
Snow vs. Ice on the Roof
Snow will typically add more weight per square foot of roof space than ice will. A roof covered with a clear sheet of ice adds weight but not as much as roof covered in a foot of snow. The real problems begin when ice and snow combine to not only add weight but form ice dams. Working together, they can ruin eaves, roofing materials and interior structural wood.
Depending on the region in which you live, heavy snowfall and ice buildup may be a reality you are forced to contend with. Letting a large amount of snow sit atop your roof for an extended period of time is not advisable, nor should ice be allowed to build up at the eaves to trap moisture behind it. Because it is a fact of life in some parts of the country, the best protection against it is proper ventilation and, if need be, professional snow and ice removal.