Michael Thomas
07-15-2008, 05:05 AM
Is this a approved underlayment for a comp shingles?
The material in unadhered and very flexible, it feels (and looks on the underside) similar to ordinary black 4mil plastic sheet.
At other locatons there was no underlayment at all, there were no drip edges at any location I checked, and the roof was a low-bidder job in other ways (including retaining existing shingles in areas where it would have been little additional effort to replace them). So it would not have surprised me to discover that the "underlayment" is just 4mil plastic, however the textured upper surface and white stripe suggest the material was manufactured for some specific propose. But would the plastic underside not act a a vapor retarder to trap moisture against the sheathing?
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Also, given that in other areas there are two layers of sheathing visible at the eave I'm wondering if cut gutter hangers above some portion of the roof just indicate a gutter replacement, or if the lower portion of the shingles may have been replaced for some reason - though the shingles across the entire field of these roof sections appear identical.
The material in unadhered and very flexible, it feels (and looks on the underside) similar to ordinary black 4mil plastic sheet.
At other locatons there was no underlayment at all, there were no drip edges at any location I checked, and the roof was a low-bidder job in other ways (including retaining existing shingles in areas where it would have been little additional effort to replace them). So it would not have surprised me to discover that the "underlayment" is just 4mil plastic, however the textured upper surface and white stripe suggest the material was manufactured for some specific propose. But would the plastic underside not act a a vapor retarder to trap moisture against the sheathing?
-----------
Also, given that in other areas there are two layers of sheathing visible at the eave I'm wondering if cut gutter hangers above some portion of the roof just indicate a gutter replacement, or if the lower portion of the shingles may have been replaced for some reason - though the shingles across the entire field of these roof sections appear identical.