Synthetic underlayment for a metal roof
I’m looking for some advice sorting through the various options on underlayment for metal roofing panels. Most articles are either “synthetic vs tar paper” or “why our product is the best” (biased).
Adding to the confusion are mixed information about what can and can’t be used with metal panels.
The two issues I keep finding are a) water proofing is more important on metal (water is more likely to get (blown?) in under the ribs of metal than with shingles) and b) metal gets hot and you need a heat resistant underlayment that won’t melt.
The climate zone is 4a (GA/TN area), and the roof is vented with continuous eve and ridge vent and insulation on the bottom chords of the trusses. We are thinking we will be using furring strips rather than screwing the metal directly to the roof. Decking is 5/8″ CDX.
All the roofing guys want to use a synthetic product. (It’s lighter and saves labor, which is good for them, but I want the job done right so when they are paid and gone and it’s my problem, there isn’t a problem….). They all say Grace Ice and Water Shied (stick on) is a waste of money, even on the edges because ice really isn’t an issue. Not sure about that. :/
Some say “roofs never had underlayment before [insert time period]” and underlayment doesn’t really do anything once the finished roof is on. Not sure about that either. :/
So if my goal is to get a quality underlayment that will last as long as the metal panels (which is think is 50 years), but not needlessly waste money, is there a specific product or product combination that is proven in this application?
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