29ft coachman rehab help!

Hello, new to the forum. I have a 1985 Coachman 29ft trailer. it was given to us by a friend, with extensive water damage.  I sealed the roof first off, so I could dry it out. used an elastomeric coating and pretty happy with the seal.  now that it doesn't leak anymore I decided to tear into the inside paneling to see how bad the damage is. wow, the 2x2" base board that runs the perimeter of the trailer is gone, rotted away. this caused the floor on one side of the camper to sag, as it hangs over the frame a foot and there is no support on the outside besides a few gussets (up to 10ft apart).  The floor seems to be a layer of super thin plywood bottom with 2" hard blue foam, and another layer of thin OSB on top. I have never seen a floor like this there does not appear to be any joyces? instead the blue foam holds all the weight I'm assuming (pretty tough stuff BTW).

I need to know how to rehab this trailer, I need to jack up the whole sagging side (1/2" to 1"), replace the base board, scab in new stud bottoms, etc. what's the best way to do this? should I remove the siding?

and what I cant seem to figure out, how does the top layer of flooring tie into the wall? did the top layer of OSB go under the studs? or is the floor a separate piece from the walls on these? the 2" hard foam "floor" really threw me off and the wall bottoms so far are too rotted to see how they went together.

Thanks in advance for any advice, I will try to upload pics later.

I guess I am a little overwhelmed. last night I spent about 2 hours staring at the rot and drinking a beer, and wondering what I got myself into...

I suspect your task is not economically viable either for $ or labor. I'd scrap the unit and move on. One example problem is that the blue foam is not the actual structural element (bending wise). What you have is a laminate where the foam provides a stiff structure in compression between the strongly bonded facing on each side. It functions like an "I" beam where the foam corresponds to the web of the beam. There are likely also at least some structural beams embedded in the foam. To repair you will probably have to completely remove the plywood facings and bond (glue) new ones to either face. That needs to be near a solid piece covering the entire rv. That is, remove everything inside and the side walls (likely the same construction) and then redo the floor, probably with all new materials. etc, etc, etc.

Ernie

I believe Ernie is right, the only thing more expensive than a cheap RV, is a free one.

It was easy to get into and it's easy to get out. I'd consider selling off parts. Depending on your property and abilities to deal with a rotted out aluminum skin box you may even sell the axles off it. I rebuilt an old TT and sold a few things such as a torsion axle, heater, etc. I  more recently sold a working 10 cu ft Dometic in very clean condition for $450. If I didn't do that then I would put an ad on Craigslist for "Free to good home". Not that I haven't repaired a water damaged RV but it all depends on how bad it is. That one is too far gone.

That's fairly typical construction for a cheap trailer, which the Coachmen was. The floor is overlaid on a minimal subframe and then the sidewalls are added on top of it. Difficult to fix extensive floor damage except via a total teardown of the walls and complete rebuild. 

Unless you enjoy the challenge of the rebuild,  you would be better off junking it and buying something newer and less damaged.  There are a lot of them around at very low prices, even at RV salvage yards, and some of them only 12-15 years old. Dealers don't want rigs that have sagging ceilings or other obvious defects, but a competent DIY person can make them new again if they know what to look for.