The bench wall supports are rotted? Yikes - sounds like they - and the floor - must have gotten wet.
To replace the wall supports I recommend this:
- Remove the old ones. With a hand chisel or sharp edged putty knife carefully pry them off.
- Cut new supporting tabs from plywood - not particle board (!!!). If possible, use the original tabs as a template. If they are not usable, then make templates out of cardboard, adjusting the shape by trial and error until you get it pretty close.
- Clean the side wall where the tabs attached, removing all traces of old wood, adhesive, insulation, etc. Use coarse sandpaper, a wire brush, or even a chisel if necessary.
- Wash the area with soap and water and than rub it down with acetone (follow the precautions on the acetone label)
- Buy some decent quality epoxy and mix it up. Using a brush, cover the wall area with a nice thick coat of the epoxy. Do the same with the tabs. Press them into pace. Use plastic tubs or buckets cut to the right height and shape (or some other creative way) to make sure the tabs stay where you want them to be. Do this before you start with the epoxy. Dribble the epoxy mix into any and all gaps between the wall and the tabs. Don't worry about the plastic, the epoxy will not stick to it.
--- An alternate to the epoxy is a good quality polyurethane adhesive, such as Loctite PL Premium Construction Adhesive. (I do NOT recommend Liquid Nails for this application). If you go this route you need to make sure that the tabs are firmly pressed up against the side walls while the adhesive cures. You could cut a couple 2x4s to length and wedge them across the trailer, pinning the tabs in place. All other steps remain the same.
The floor is a whole other issue. The rotted sections need to be removed. If the rot does not extend beyond the base of the benches you could just cut replacement panels and glue them over the remaining parts of the floor in that area. Give it all a coat or two of oil based
paint - top and bottom - after the glue dries. You'll want to completely seal up any exposed original flooring or it will just suck up moisture like a sponge.
If the rotted flooring extends beyond the benches you have a bigger project - but the basics remain the same. You'll remove the rotted material and piece in a plywood replacement.
If you get stuck - post some pictures of what you have after you get the rotted stuff removed and you'll get some suggestions from others who've been down the same road.
Good luck. I think this is a pretty common adventure for anyone with a previously owned
Scamp.
Oh yeah - try to determine how things got so wet to begin with. Maybe the
windows were left open in the rain - or maybe there are
leaks. You might hose the whole thing down and then look for any
leaks.