Quote:
Originally Posted by Phobia
You'd have to check with Johnson County.
That ice and water shield won't prevent dams but it will help prevent penetration into the attic/decking should a dam form.
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Residential
Ice barrier. An ice barrier (ice dam membrane) that consists of at least two layers of underlayment cemented together or of a self-adhering polymer modified bitumen sheet, shall be used in lieu of normal underlayment and extend from the lowest edges of all roof surfaces to a point at least 24” inside the exterior wall line of the building.
An ice dam protection membrane should be applied starting at a roof's eaves and extending upslope a minimum of 24 inches from the exterior wall line of a building. For slopes less than 4:12 (18 degrees), a minimum of 36 inches is recommended. See Figure 1.