Spongy floor

[Smidsy47]

Hi all, this is my first post so hope its ok...

i recently bought a Swift Challenger 470SE 1996ish, i got it very cheap as although it is in very good condition it has a spongy floor by the shower room.
Someone has had a go at repairing the floor in the past by drilling through the carpet and using expanding foam which resulted in still having a spongy floor but with big lumps under the carpet, i have pulled up the carpet and cleaned the mess up, and drilled out as much foam as i can:
I have 3 questions
1, i bought some floor repair resin and wooden plugs, will this resin expand when activated with water, I do not want the lumps back?
2, I would say the carpet is original by the way it is neatly laid under all off the cabinets and fixtures but on ripping it up I have found newspaper underneath which was a surprise, would Swift have used this method from new ?
3, How thick is the flooring, i do not want to go right through the floor, i have some drill stops but dont know what depth to set them ?

Thanks in advance
Dave

 

[glenno]

I have repaired several caravan floors. The 2 types of glues mostly used are 2 part epoxy which does not expand and should be used if the delamination is not so far advanced such that the gap between the wood and the foam is still small. The other type is expanding foam used when the gap between wood and foam is large. If used properly both types can restore a floor to solid as new condition. The foam type does expand back through the plugs a bit but this should be sanded smooth when set before replacing the carpet. You don't need a drll stop its patently obvious when your drill bit hits the ply on the other side of the foam. Most floors are 40 to 50mm thick. I doubt swift used newspaper.