Ice dams occur when roof gutters becomes clogged with ice and debris. As water from rain or melted snow runs off of the roof toward the gutter, it becomes trapped between the ice inside the gutter and the roof shingles. With nowhere for the water runoff to go, water can move back and underneath roof shingles. Once the water travels underneath the shingles, it may remain there for an extended period of time undergoing a long series of freeze/thaw cycles. Should water remain underneath the roof shingles, it won’t be long before the water begins to create roof deck damage and wood rot.