Is it necessary to seal the floor slab inside with bitumen membrane?

Good evening,

I have a question regarding the sealing of the floor slab.
Is it always necessary, in principle, to seal the inside of the floor slab with a bitumen waterproofing membrane?
I see many shell constructions where the sanitary and electrical installations lie on the raw floor (so no bitumen underneath).

Our construction is as follows:
- Geotextile
- 60 cm foundation cushion
- Blinding layer
- 12 cm insulation
- 22 cm floor slab
Later, an additional 20 cm floor construction will be added.

Can someone tell me something about this?

Whether and where sealing is necessary depends on what it has to achieve: the floor slab can also be sealed at the bottom (with foil or otherwise) against, for example, rising ground moisture, which is why this sealing is no longer visible later.

One only needs to protect the floor build-up layers against residual moisture from the floor slab itself, which can then also take place on a different level.

On my BP there is a wall barrier membrane at the edges; inside, everything is directly on the BP. In addition, the first row of stones of the exterior walls was made with 24 cm stones (normally 42 cm) and the transition between the floor slab and the first row of stones was sealed. XPS is placed in front of the base.

Between the insulation and BP there is still a thin foil.