The low spot I'm concerned with is basically a 1/4" valley over the span of about 3 feet. Subfloor is 3/4" plywood.So you want to lay down a non compactable material that's sure to flex?
How low are these low spots?
What's there now for a subfloor?
If I can't use sand, I'll just go back to using floor leveling compound; I just wanted to see if anyone else has ever used sand for this purpose, since it sounds so much simpler. I thought it probably sounded too good to be true though.