Casting a root cellar roof

[CCGDE]

Hello, I am in the process of building an earth cellar, I have built walls with Finja concrete hollow blocks 200x190x400mm and plan to cast a roof.

Question 1: Can you cast in a low-sloping arch form inside but have a flat roof on the outside? Will the strength be the same? I know it may not be optimal, but I don't know how else to build the form.

Question 2: How thick should the cast be? I have a width of 280, length 450 with an extra wall inside. I've been thinking around 15cm as the thinnest, it might be over-dimensioned but better more than less.

The idea is for the roof to last a long time and support at least 50-70cm of soil on top.

I am aware that the amount of concrete will be large, and I'm not directly worried about successfully casting it, I just want a bit more insight into the thickness and if the vault idea is feasible or if the whole plan is foolish. I'm open to suggestions and constructive criticism, questions.

Sorry for the somewhat vague description. Thanks in advance.

 

[bossespecial]

You don't have the option to attach a plan sketch/drawing. It is a relatively large roof with a lot of load on it, so I recommend that someone calculate it.

 

[CCGDE]

You don't have the option to attach a floor plan/drawing. It is a relatively large roof with a lot of load on it, so I recommend someone calculate it.

Thanks for the response with the first question I was thinking like they cast here
https://www.dinbyggare.se/bygg-en-jordkallare/

Ovanskiss