There is no real easy way to do this.
Our TT's rely on the structural integrity of all the components together as a unit to withstand flexing and twisting as we go down the highway.
The floor is a critical part of holding it all together. It really needs to be in one piece rather than being cut up into sections and pieced together.
The floor is built and the flooring put down before any walls, cabinets, partitions etc are put on. Then everything is put down on top of the floor and screwed down.
I rebuilt an old leaker years ago and I literally lifted all the walls completely off the floor and replaced the plywood and most of the joists. I then put everything back down onto the new floor.
It was a huge project and a very difficult one to do.
The short answer for you when replacing the rotten floor is to cut away where you can and install solid blocking all the way around the cuts, gluing and screwing the blocks both to the remaining old floor sheeting and also the new plywood to it. The idea here is to make the new plywood part of the old and very securely fasten it together so it does not move.
A lot of work but it can be done if you are diligent.
Only problem is I can almost 100% assure you that the floor will be rotten underneath cabinets, walls etc. which will entail removal of all things in the way.
My rule of thumb now is that if you find a leaky rotting RV for a good price, let someone else buy it. It is simply not worth the work and effort to fix.
2007 GMC 3500 dually ext. cab 4X4 LBZ Dmax/Allison - 2007 Pacific Coachworks Tango 306RLSS
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