I am getting ready to design a slab house. I want to build a 30'x60' one story t-111 sided house. My question is, I have been reading about fiber re-inforced concrete. With a monolithic pour do I need to pour thicker on outside edge than the 4" slab thickness. Building codes don't come into play, very lax. Thank you

In some parts of the country you will need frost footins that will require a separate stem wall or shallow frost proof foundation system.

In some parts of the country there are thick organic material layers that need to be removed.

In some parts of the country the soil is unstable and piers and gradebeams are installed and the slab is supported by them and not by the soil.

I don't know of any place that you can build without some kind of footing to support the wait of the walls and that includes interior load bearing walls.

In most cases it best to use to whatever technique and practaces that are common in your area.