So on Matt Risinger's The Build show on Youtube, he has been in Switzerland and he showed a building where the subfloor was three layers of 2x6 (that's a guess from looking at the video) spaced out BOARD - GAP - BOARD, etc running North/South, then the next layer being BOARD - GAP -BOARD, etc running East/West and finally another N/S layer. Then the entire floor filled with sand. On top of that you put the finished floor.

Just wondering if anyone has seen something like this, knows what else the floor has in its design beyond the crisscross boards, and is it a possible alternative to a concrete slab in an area not controlled by county building codes?

Thanks. Just really curious.