Folks here is a website of a company named SPU SYSTEM that deals with multi purpose "Panels" that we are going to use for the floor, sides and ceiling...
I know that the pages are mostly in the Finnish language however from the photos you will at least get an idea of the type of panels we,ll be installing.
http://www.spu.fi/index.php?sivu=2057
I,ll post the actual photos once we proceed.
They have a tongue and groove on them to install tightly against another panel using what we call "seaming foam" and they can be cut easily and applied . Both sides of the panel have aluminum backing..The thickness available is from 30 mm to 170mm.
We use these here for our Saunas as well ... so that also explains how good they are in preventing dampness ... in the wall structures...and providing insulation with a good r value.
The Rv and Automobile as well as the Yacht building industry here uses them too..including home building...along with shower areas.
http://www.spu.fi/tiedostopankki.php?kansio=2455
Classic Finn