Nothing highlights construction shortcomings like severe winter storms. Too often, possible problems are neglected during the construction season when winter and its bad weather seem far removed. The winter of 1999 produced many ice dams on shingle roofs in central and eastern Canada. The resulting leaks caused widespread damage to ceilings, walls and interior .furnishings of many homes.
Roof ice dams. It's not really a roofing problem.
Canada, Solplan Review, May 1999, pp 6-7.