RV Repair: Thor Aerolite 21RDB floor rot, thor aerolite, chassis frame

Question
I purchased a 1998 Aerolite 21RDB a couple of years ago. There was evidence of a leak at the left front and I sealed a leak that started at the top of the stone guard frame. Being a worrier, I ran a dehumidifier constantly inside the trailer when not camping and kept a look out for floor rotting, particularly in this area. The other day I noticed that an attachment between the chassis frame and the floor had pulled loose and there is evidence of rotten wood. Since I believe that the floor, like the walls and roof, is made of a plywood/foam sandwich, can this be repaired? If so, must it be done by a repair shop or dealer?
Also, with the outside of the floor covered with what seems like sheets of thin aluminum, does this not hold in moisture? Should it be replaced with a more breathable material?
Thank you for any help and advice you can give me.
Ian Renton
Tampa, FL

Answer
The key to leaks is to obviously find where it is coming from. This can sometimes be difficult, so overkill as far as sealing is concerned is not always a bad thing.
But first you need to determine how bad the floor is.
I would remove the cabinetry or whatever is above this area you are talking about, and see how extensive the damage is. The problem is that most units are built by putting the sidewalls on top of the floor. Therefore, if you have to replace plywood, there is nothing to attach it to after it has been cut out. You would need to cut out the bad spot, but in some type of backers to attach the plywwod to, and then put everything back together. While you have it apart, you may be able to tell where the leak is coming from at that time. If it is more than just a small section, your best bet would be to get some estimates from professionals. Many times, smaller RV repair shops are less expensive than a dealer. Shop around, if you have to.
I hope this helps you,
Dave