I have an old summer cottage with three rooms on the ground floor. The floors were directly nailed into beams that lay directly on the ground. No insulation. In two of the rooms, I have excavated and insulated using different techniques. In room 1, I placed about 30-40 cm of leca balls as a capillary break, on top of which I laid fiber-reinforced self-leveling compound about 20mm, insulated the beams, and laid Siljans wooden floor. In room 2, I did it in a more classic style with gravel, concrete slab, styrofoam, chipboard, and then Siljans wooden floor. In room 1, the joints on the wooden floor have now risen. 
Why?
Which solution would you use for room 3?
Why?Which solution would you use for room 3?