Metal & Copper Roofing Blog

Can You Use Standard Ice & Water Shield Under Metal Roofing?

Someone reached out recently with a specific question about the choice of ice and water shield her contractor was using with the new copper roof over her three bay windows. She noticed that the high operating temperature for this particular product was 194F and worried that wasn't high enough, posing problems down the road, so she reached out for our insight.

High-Temp Ice & Water Shield

Unfortunately, her concert are well justified. Manufacturers of fully adhered roofing membranes (AKA:  Ice and water shield) designate different versions for different types of roofs. It’s clearly specified on the label whether or not a given version is intended for installation under metal roofing, or other types of roofing materials. For use beneath metal roofs, they make “High Temp” or “HT” versions and for under asphalt shingles and concrete or synthetic roofs, they offer regular versions.
Because metal roofing heats up (when in direct sunlight) and cools off quickly (when not), any material it touches should be capable of very large swings in temperature. That's especially true for ice and water shield underlayments, since they use asphaltic compounds as their primary waterproofing ingredient. When they're installed under metal roofing, they should be formulated to withstand high temps, because if not they can melt and drip out under the metal. That's not only entirely self-defeating, it's also unsightly.
Make sure your contractor uses an HT version, or else problems are likely ahead!


Topics: metal roofing