It’s not large enough to be necessary by code here, and I’ve not seen professional companies use anything when I’ve had larger patios poured in the past either so I was scratching my head.

Thanks for this

Was planning to contact the soil, add 2-3” of gravel, then compact again before pouring. I’m thinking the felt paper may be the best material for me as the hose slab has some decent chunks of concrete that came through the underside of their forms that I’ll be pouring over. The paper would let me wrap around that as opposed to a fiber board.

This is great information, thank you!