On Sat, 25 Oct 2003 14:01:41 -0400, ge wrote:

My question is regarding the ice barrier for the valley. We sometimes get
fairly heavy snowfalls, and a fair number of freeze-melt cycles over the
winter, and ice dams are a problem. The valley ends halfway down the
roof. So, at its bottom, one side is over the dormer overhang, and the
other is just the main roof sheathing. The valley discharge just flows
onto the main roof.

Perhaps you do have inadequate ventilation ( rusty nails). Ice dams
are caused by inadequate insulation and ventilation. You might want to
address these issues while your tackling your roof.