Mystery Brown Ooze - is it water damage?

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fifthwheel5

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Dec 26, 2018
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Kia ora everyone, all the way from sunny New Zealand,

I am currently remodelling an old fifth-wheel that used to be used as a mobile clinic. It has a mystery rust-coloured, chemical-smelling brown ooze coming down from several old rivet holes in the ceiling. I've attached some photos for your viewing pleasure.

The roof is fibreglass and seems to have been neglected for a long time. Beneath that, it has spray foam insulation, and what I believe is a plywood/fibreglass ceiling.

I took out some internal walls by grinding off the rivet heads. Not all of the rivet heads are oozing, which gives me some hope. There are also no other sign of water damage, such as yellow stains or visible water tracks. There are never any drip marks on the floor beneath.

I wondered if anyone out there had seen this happen to them before and knew what on earth it might be?

Thanks very much!
 

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Welcome to The RV Forum!

Yes, that looks like water leakage.  The seeping water is dissolving part of the foam insulation and/or the plywood, giving the rusty look and smell.

If you have a fiberglass roof, a long term fix would be to coat the entire roof with Elastomeric Roof Coating.  It expands slightly after application and provides a bit of extra insulation while reducing rain noise in addition to stopping water leaks.

At the very least, apply it or self leveling lap sealant around all of the roof joints.  Be sure to apply a cover coat to the flanges around all of the roof penetrations.
 
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