Can earthen floor fix a concrete foundation issue

We are doing a conventional build but have run into a bit of a snag. Just by a fortuitous event with the electrician needing to break a portion of the concrete we found the foundation was poured with less than what it should have been but the foundation passed inspection. Now we have been given an option to add an additional 3 inches of concrete to fix it conventionally but wanted to know if an earthen floor might be an alternative because the concern is moisture and cracks due to clay/sand soil. I would love any thoughts that would help. Thank you

A bit more infprmation about the situation will make it easier to discuss

Okay! The concrete trade poured 2 1/2 - 3 inches but should have been 4 inches internal house. It’s a prolific pour so the outside structure is sound but there is cracking and the engineer says 2 options pour 3 inches of concrete over existing floor but we have framed, plumbed and completed most of electrical we just so happened upon this error based on an electrical error the other option is use gutters to protect from moisture to prevent heaving later but I thought maybe earthen floors could be a better option for the flooring we use on top of the slab... hope this helps... Thanks

Hi Valerie, and welcome to permies!

When you say "prolific pour" are you inferring that the foundation and slab are all one unit? Is this a post-tensioned slab by any chance? The reason I ask is because in a monolithic, and especially post-tensioned setting, the integrity of the slab is part of what keeps the foundation from shifting. If the foundation members are sufficient on their own and not relying on the strength of the slab tying them together, that would say to me that putting an earthen floor on top wouldn't be a problem...IF you keep tabs on moisture levels below grade.

So, need more info, basically.

Yes sir all one unit. All outside around is a stem wall

What aproblem to have.
Its not often I suggest bringing in legals but this may need them.
Depending on who is the main contractor, the concreter may be resposible for rectification.
If you have a good ceiling height, a 3 inch extra slab, with mesh I would expect, should work and be ok.
If the Engineer is happy with that, its a good start.
But who is going to pay?

Yep, concur with John here. If it's all meant to act as a unit then the contractor stuffed up. Was there an inspection that some local body signed off?

Yep it passed inspection but once the concrete dried there was no way I guess to know.  We are doing are legal due diligence thought.  Thank you so much for thoughts greatly appreciated

I simple core test will show if the concrete is to the correct thickness.
I have laid slabs, the Engineers can come and inspect it all good, then the concreter just either lowers his boards or screeds off below the boards.
Its simple to cheat if you want.

The other trick is to have lower cement content in the mix, saves money and is sometimes not picked up.
So maybe teat for compressive strength as well.
I would be talking with the concreter and seek a simple solution.
Testing takes time and money.
A sign at the front explaining what a terrible job may work if talking gets nowhere.