When I was young, I remember my parents house always had problems with ice dams in the winter. The roof was asphalt shingles, and had no overhang, except for a rain gutter. I remember several times water would start to drip inside the house, and then my father and me would be up on a ladder pouring boiling water on them to break them up, while mom was having a panic attack in the house. Eventually he bought some electric coils that helped, but were not a complete solution.
I've known this to be a problem for other people too, although the houses that have a decent overhang (at least one foot), seem to have less problems with this.
These days, more roofs are being covered with steel roofing, rather than shingles. I've used it on unheated barns and sheds, but not on a house. I'm wondering if ice dams are as much of a problem on steel roofs? Obviously, there are still joints between the sheets of steel, and water could get in at those joints. Yet, the steel is more slippery and ice/snow tends to fall off more than on asphalt shingles.
I'll mention that on my barn, several years ago, I did get a buildup of snow, then some warm weather caused the upper portion of the snow to melt, and an ice dam did occur at the lower edge. The nice thing about the steel roof, in a barn with no ceiling below it, is that I just took a 2x4 and banged the underside of the steel, and the chunks of ice broke apart. Then a long pole was used to pull them down.
One other thing I should mention in this regard, is that a local business had a large steel roof, which was above a parking lot. Several years ago, there was a warm spell during the winter, and a huge block of ice and snow fell, and actually destroyed a few cars parked below, (including the car belonging to the owner of the building).
This indicates that the steel roofs have problems of their own, but I wonder if the ice dams are less of a problem on a heated home?
I've also seen that they sell these plastic things that attach to the steel roofs that are supposed to keep the ice from falling. I'm not sure if that's a good idea or not. Plus those things look flimsy....
I'm looking for opinions based on what others have experienced. I'd much prefer to use a steel roof when I build my small house. It costs more, but has a much longer life span, and is more durable, not to mention is much easier to install than shingles.