Cargo bay ceiling is disintegrating 2019 Vista 29VE

[Steven_66eb7bac8eb8e]

I have finished my first year with my RV (new to me 2019 29VE) with plenty of adventures. And a puzzling challenge.
As we are readying the RV for storage, I noticed some white dust coming from the ceiling in a rear cargo bay. This dust started appearing about two month ago (August) but now I poked at the ceiling, and the blue liner came apart. As did the gypsum between the liner and the wood. This damage makes me think: water. But the wood on the ceiling currently appears dry even though the RV has been in rain lately and the interior utilities have been used (shower, toilet, sink) within the past week.
The cargo bay in question is on the passenger side, behind the rear wheel, under the outside TV and before the outside kitchen (outside kitchen is not used often.) The bed is above the cargo bay. The pictures below show the cargo bay location and the ceiling of the cargo bay.

So I am asking this group for advice on what is causing the problem, how do I fix the problem, and how do I fix the symptom (the disintegrated ceiling).

 

[Lv2Roam2]

Some thoughts: 1) Wear a mask when you get into an area like this. 2) Is this occurring anywhere else on the coach (and look at interior sidewalls directly above this area)? 3) Repost your question on IRV2 - you'll get a much larger audience (this issue is likely not unique to WBGO).

 

[Steven_66eb7bac8eb8e]

Some thoughts: 1) Wear a mask when you get into an area like this. 2) Is this occurring anywhere else on the coach (and look at interior sidewalls directly above this area)? 3) Repost your question on IRV2 - you'll get a much larger audience (this issue is likely not unique to WBGO).

Thanks Steve for your input. I have checked the interior (but didn't remove any walls) and don't see any signs of water. One of the first things I did in the RV was to re-seal the shower pan to the walls, so I wonder if this damage was present but not visible when I got the RV last year.
I have had a couple of leaks caused by the kitchen sink drain getting loose. While that is on the other side of the RV (and on the slider), I suppose the water could have made its way to that cargo bay.

 

[Lv2Roam2]

It's certainly possible that this is a longer-term issue - we never get our rigs perfectly level so water migrates 'at will' and then can take months to manifest as rot, etc. If you see no staining on the interior sidewalls and/or the ceilings of any other compartments - consider the following. Put a heater in the affected compartment and let it run for a few days - the goal is to dry everything out as much as possible to limit mold and ongoing rot. Then - with very good eye protection and face mask - scrape as much of the debris away as possible. I've used brush-on enamel paint to seal the area in my previous trailer with a 'wet area.' Some use epoxy - a little harder to apply and more cost. And keep an eye out for 'drip leaks' from any connections, etc. and short-cycle runs from your water pump that may indicate a leak somewhere. And please do post to IRV2 - there's a much larger wealth of knowledge.

 

[Bones2003]

I seem to recall other posts similar to this problem but I can't locate them. The white dust is what triggered my memory. The top liner of the compartment is an aluminum sheet that interacts with the steel parts of the frame and corrodes through galvanic reaction. There is supposedly a very thin isolator sheet or perhaps tape or a coating between the dissimilar metals to prevent this type of corrosion. Maybe this will ring a bell with someone else on the forum that can find those posts and what, if any, solution was found.

 

[Tillie]

I have the same motorhome, but a year older and I’ve not had that problem, but I did notice when I zoomed in that your little “tweeter” has fallen off your speaker on the outside which happened to mine and when I went to replace mine I realized that there was signs of just a little bit of seepage around the speaker. You might want to pull the speakers out, in fact I would replace them like I did, and see if there’s any indication moisture gets in. It may only happen under certain circumstances. Wind direction, while driving in the rain, etc. it will also give you an opportunity to peek inside there. Might want to consider a low cost orthoscopic camera so you can peek inside a little further and see it from the top I found that to be a very useful tool for an RV.
I have used the track down water leaks, and also to route wires. I had one leak that turned out to be the skylight in the shower, but the water came out by the passenger side window in the front.

 

[Morich]

We had the problem with different metals as Bones described above.
But did we have the same material as you? You talk about sheetrock but I wonder if that is actually what you are seeing?
We had it on side panels in a number of different compartments and it did look very much like sheet rock dust.
We fought it for a few years and never found a cure but over time we found it was not actually sheetrock dust but a white dust that seemed to "replace" the metal over time.
My first try was sealing it and that made no difference. Next step was cutting the damage back much like what we might do on a damaged car fender to remove the rust/corrosion before rebuild. As I cut and scraped, I found it was not sheetrock but the metal itself was turning to dust!
Our problem was in most of our compartments before we finally gave it up! Where the panel with thin blue material met the steel? Framing around the places like corners of the compartment was where it started and then worked it's way further and further in.
More like a fungus or "metal rot"?

Never got pro advise but it is my theory that there was a mismatch in the adhesive used to bonded the blue to the metal underneath.
Selling it back to the dealer who sold it to me was my solution! He didn't tell me and I didn't tell him!

 

[klook]

Galvanic corrosion. I can see it in the compartments of my class C. Water or moisture will make it worse. I don't think there is a way to stop it. If mine gets bad I will cut out the area and put something else up to finish the ceiling.