This is a great question that came in a comment via another blog post, "Will A Metal Roof Make My House Hotter?" Our reader wanted to know if a standard ice and water barrier would work under metal roofing. The short answer? Not in our experience. Here's why.
CAN YOU USE STANDARD ICE & WATER BARRIER under METAL ROOFING?
Most manufacturers of fully adhered roofing underlayment, also known as “ice and water shield,” offer their product in two categories: regular and what's referred to as "high temp.”
I learned about the difference when a customer had a problem with a black substance oozing out between the metal diamonds on his roof. It was an issue related to the ice and water shield installed by his contractor. He had used the regular kind, and it was actually melting in spots where it touched the metal diamonds, which were directly exposed to the sun for extended periods throughout the day. Fortunately, there as an easy fix - he switched to the high-temp version of the same manufacturer's membrane.
In most cases, the high-temp versions of ice and water are labelled for metal, or designated high temp or another term that indicates their suitability for use beneath a metal roof. And to avoid finding yourself in the same spot as my customer, I recommend ensuring your contractor is using the right kind of membrane beneath your metal roof before installation is set to begin.
Learn more about metal roofing with our free re-roofing guide.