I had to remove some dry wall due to black mold in the bathroom around the bath tub. When cleaning up I found that there is actually no concrete foundation, instead just dirt. Is this normal?

I had to remove some dry wall due to black mold in the bathroom around the bath tub. when cleaning up I found that there is actually no concrete foundation, instead just dirt. Is this normal?

If you're referring to the tub dap-out(see image) behind the drain that's normal, however, the tub itself should be set on the cement slab. Regards, Tom