Metal Roof Bleeding Underlayment?

Hey guys have a quick question. I inspected a metal roof today that appeared to have a black substance dripping down. Have any of you seen this issue before? It was dried out, and appeared to have happened a while ago. Is this the underlaymen

t getting too hot? What might this be due to? Insulation or ventilation issues? There is no attic space, as it is a log home with log rafters and T&G.
Thanks and let me know.

they hay have used KARNAK or similar sealant to the underside of the metal panels when it was installed, or it was leaking and added it later.
Thats my guess. its not underlayment leaking. as underlayment would not do that, Not even tar paper. it would never get hot enough for Tar paper to melt and drip like that.

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No, never seen that.

But sometimes they use self stick membranes, bituthene. Maybe a cheap version of that, not rated for under metal roof, did liquify? It’s remarkable even and consistent, which argues against a bad patch.

Now that’s not a standing seam roof… it has screws. Meaning, the screws could be removed for inspection and replaced (with new screws) without doing permanent damage. Not that your drone could do it…

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Observation: Roof: Metal roof: Bitumen, viscous liquid, volatile bleed-out at metal roof temperatures.
No adverse visual conditions observed the day of the inspection.
Recommend: A licensed roofing contractor Annually Monitor for further bleed-out.
Act upon any referrals offered.
Limitation: Inspected using a drone.

@wjones18 is probably on point with a sealant applied to the underside of the panels.

Also, it appears the cut edges of the panels are beginning to rust which is a problem.

Thanks everyone for the replies! Sure appreciate the help.

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Something else interesting to notice, is that the bleeds all line up with the corrugated sections. This would seem to indicate that it is a tar sealant that was used along the flat edges, and the raised corrugated was the path of least resistance, as they would not be completely filled in with sealant.

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I learned on a roofing job: edges cut with a grinder will rust. Those cut with shears won’t. Bonus points for whoever can explain why (weekly quiz)?

I know when you use a grinder, dust will be left behind that will rust, same as when you leave the little shavings from running in the screws atop the panels, they rust. I suspect when you grind, you also grind off all the protective coating.

Regular grinding disks have iron in the abrasive. You can use grinding disks designed for stainless steel, however.

Just a guess, but because of the heat?