What is an ice and water shield barrier, and is it the same as an ice barrier?
Short answer. An ice and water shield barrier is a self-adhered waterproof membrane installed on the roof deck under the roofing, and the building code calls it an ice barrier when it is used at the eaves to stop ice dam leaks. Manufacturers market the same kind of product as a leak barrier, and in Georgia it mostly goes in valleys, around penetrations and at walls rather than serving as ice protection.
Three names for related things
- Ice barrier, the code term. The residential code requires an ice barrier at the eaves where the local jurisdiction says ice damming is a hazard, running from the edge to at least 24 inches inside the exterior wall line. Self-adhering polymer modified bitumen membrane is the usual material.
- Leak barrier, the marketing term. Shingle makers' name for their self-adhered membranes, and sometimes for heavier non-adhered products used in the same spots.
- Ice and water shield. Originally one product's brand name, now the everyday term for any self-adhered roofing membrane.
How the barrier works
The rubberized asphalt layer bonds to the deck and seals around the shanks of nails driven through it. Water that backs up under shingles, from ice dams, wind-driven rain or a valley clogged with pine straw, meets a sealed surface instead of the nail holes and seams in ordinary underlayment.
Not to be confused with
- Water-resistive barrier: the house wrap behind siding.
- Radiant barrier: foil on the attic side of the decking that reflects heat.
- Vapor barrier: a layer that limits moisture moving through walls or ceilings. Self-adhered membranes are nearly vapor-tight, one reason attic ventilation still matters.
See ice and water shield in Georgia and roof ventilation basics.