[wil6707]

Thanks for the replies folks!  Good to know about the windshields Clarke.  I'll check that out.

Hey Mike - The floor in mine is (or was) just 3/4 inch plywood, but what they did was staple some 16ga. aluminum to the bottom of the plywood before they put it in, so that is why you see that aluminum in the pics.  I pried up the wood and left the metal.  That way down under the bottom everything still looks the same and you have that protection.  

There are metal braces that run across between the walls of your water bay that the floor is screwed to.  The plywood goes under the wall and lays on a piece of 2x2 (ish) angle iron.  From that angle iron to the first brace on mine is 10in and the next one is at 24.

I took some pics for you since I happen to have just cut the floor out yesterday.  Don't be like me though and not think about where the braces are before you cut, otherwise you will end up with no support under your floor seam.  I may have to cut out to the next brace.  My rot goes into the coach pretty far though.  Yours may not.    You should be able to see all this from the basement though so I'd take some measurements beforehand.  

Oh and the way I cut out the floor was to just set my skill saw to exactly the thickness of the plywood and then plunge cut what I could.  Then I just finished it with an oscillating saw.  From what I have seen with mine it's pretty standard thickness sub floor.  I'm putting back Advantech which is waterproof and it is the same thickness minus the vinyl.