All of the icicles forming on homes give the impression we are living behind bars at times. In the photo below, an ice dam has formed in the rain gutter.(http://mahoningvalley.info/forum/index.php?action=dlattach;topic=7666.0;attach=4129;image)
Anatomy of a roof ice dam
(http://www.lyonscontracting.com/blog/wp-content/uploads/2009/12/roof_with_ice_dam.jpg)
That's why roofing should be done by professionals who install a waterproof liner on the roof before installing shingles.
Preventing Ice Dams
http://www.thisoldhouse.com/toh/article/0,,1131346,00.html
Fast Fixes for Ice Dams
http://www.thisoldhouse.com/toh/article/0,,1131314,00.html