We are thinking of putting rubber shakes on our new home...pitch 9/12..we are building a two layer system...plywood over roof rafters..2x4's on edge with another layer of plywood...then a Ice and Water Shield over all, but I have come across a product "RoofAquaGuard UDLEX" or another one that is basically the same "Roof Top Guard II" they say to use the Ice & Water shield in high risk water penetration areas ie: valleys and then use the Roof Guard over the rest. Has anyone used these products that can give me some direction on them. Another question is the dampproofing material that is put on ICF the same as Ice & Water Shield??