There are certain parts of construction where you can say I don’t want to spend money on the expensive tile lets use the cheaper stuff.
THIS IS NOT ONE OF THOSE TIMES!
This is going to be the most important part of your construction.
In order to begin you must get plans from an architect and plans from a structural engineer. You need to look at your soil so please see my comments below. You will also get plans from the MEP engineer for any services which must enter. Be prepared to have a sit down talk with the structural engineer. You need to tell them that you want to over build the foundation. If the walls need to be 12 inches thick make them 16 inches. If the floor must be 10 inches thick make it 14″. Tell them to put it in the plans and have them calculate volume of concrete based on this. Ask them for a mix of concrete with a higher strength than required. If you know the volume of concrete you should have you can verify that the job was done right because that is how much was poured. Don’t ever back fill with soil. Use concrete, its not that expensive. Make the walls thicker and make the floor thicker. Concrete is relatively cheap. This is your insurance policy. Get an outside inspector to inspect the concrete at pour. A lot of companies say they have their own tester. That’s nice. People don’t make mistakes as often when others are watching.
Soil can be a problem. Get it tested before you build. You may want to include this as part of a pre buy inspection. If it is bad and you have to put piers you can either put piers to bedrock or stop and walk away. Do not build without proper support. Consider hiring a soil specialist to help you with soil issues.