I am using Foamular250 under my basement. With CA6 fill underneath, is there a problem over time with the weight of the concrete pushing the uneven contact points of the CA6 stone compressing the Foamular250? I am wondering if I should get a few loads of sand to fill the gaps between the stone - or not to worry about it.

what is CA6?

CA-6 is usually 3/4 or 1" crushed stone with fines.

Generally speaking it's somewhat better to use cleaned gravel with no fines under basement slabs, since the fines wick water and cause it to drain more slowly. Adding sand would make it wick even more.

Don't sweat the localized denting of the stones into the XPS- it's negligible.

ok cool. Yea CA6 is what you say. We had tons of rain this spring here in Chicago so I'm at 100% settled I was just curious about foam compression. And yes, I already got 20mil for the basement and 10mil for the garage.

I am gluing 1inch thick against the basement wall, 6" high, putting 1" over the footing, rest is two inch. I know the edges are more important but for the floor height this is what I am doing. Should be ok. I will keep the tubes 18-24 from the walls...