I dont use sand inside their house. I have a good size run, about 35'x12' and another that is 15'x5'. I put 3 cubic yards of sand altogether in the runs...about 4-5 inches deep. I'm so glad I did and shouldve done it a long time ago, but I had a big dirtpile to get rid of first and that was what I used after "gully washer" thunderstorms washed it all out. The sand absorbs the rain without washouts and dries quickly. No more fly problems neither, easier to scoop poop as well. Here, I paid $25 per cubic yard, including tax. I cant help you regarding stone, sorry.