Expanding insulation in the belly

[AUwing2]

I need to fill a couple openings in the frame and underbelly that were created when a new leveling system was installed n our Jayco last fall. The grey stuff Jayco uses looks like open cell but anything I’ve seen at the big box store causes concern that it would become a sponge after a while. Any suggestions?

[AUwing2]

Thanks for the suggestions

[shum02]

Painting it usually seals it. You just have to be careful with what you paint it with.

[agesilaus]

Link

But on the other hand normal polyurethane foam is water proof but maybe not resistant to direct impingement of flowing water like the waterfall foam. And a lot cheaper. However waterfalls in the RV belly are quite rare.

[Colo_Native]

I used pond foam it is water proof.
https://www.homedepot.com/p/Beckett-12-oz-Waterfall-Foam-Sealant-FM12HD/100206907