6 mil poly sheet as underlayerment

I came across this house during my inspection and i was inspecting the roof. At first i thought there was no underlayerment at all but when i looked a little further i seen what appeared to look like 6 mil polyethylene 3 inches away from the edge of the roof. I’ve never seen or heard of 6 mil poly being used as underlayerment. Does anyone know if that’s a problem?

Where are you located and year built? any photos?

Edmonton, Alberta, 1986 and yes however i cant pull them off of the software.

Any chance it was rubberized? Say for an ice dam?

Without photo’s it will be difficult to help.

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poly would be bad for a roof. as it does not allow air to breathe. the condensation would just rot out the decking over time.


This is the best I can do. It’s a photo of the photo so the quality isn’t great but we’re I have the arrow is the sheet. It’s very see through hence why I didn’t think there was an underlayment.

I do not see 6 mil plastic or any underlayment.

Careful how you report this. You had significant limitations on what you could see and where you saw it and how far back you lifted the shingle. Because I doubt to encircled the entire perimeter looking for it.

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I know its very hard to see but i actually felt it before i seen it. Hell it might not even by 6 mil poly.

Possibly not. You can say things like “I lifted a few shingles at (front? rear?), no underlayment was visible for several inches along the roof edge at this location. Underlayment should be continuous to the edge. Additionally, there was no visible drip edge flashing at this location which has been required for many years. Recommend further evaluation blah blah blah”


You sir are a scholar and a gentleman. Thank you for your advise.

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