Foam insulation and aluminium.

[Robbo]

Originally Posted by alidesigner

I was assuming that you would coat the bottom and fit the deck later so condensation would form on the under side of the deck and drop onto the foam. Might not be such a big deal though.

Maybe the answer can be found at www.sprayfoam.com

thanks Steve, Ive registered on there to ask if it will attack Ally, as it doesnt seem to say specifically.

As you say, spray onto bottom plating and cover up later.
Condensation-in theory if its sealed and its closed up on a non humid day or drained, there shouldnt be any, once its gone from the trapped air?