I know this has been discussed many times and the comparison of Homasote, foam and other materials discussed. However, I just had an EPDM roof put on my shop and they use an underlayment that is easily worked yet seems somewhat denser than Homasote. I would imagine that it has some good properties for stability given it is directly under roofing materials. Has anyone had experience with this material, both positive and negative and know of normal sources for purchase. Did not see any in the big box stores although I didn't ask either.
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