Railing-supported stairs on screed or raw subfloor?

Hello everyone,

Do railing-bearing stairs have to be fixed on the raw subfloor, or can they also rest on the screed? I have two offers for such stairs, and both stairbuilders want to have them rest on the screed, as the compressive load is not too high.

One stairbuilder writes that the starting post stands on the screed and is fixed with a pin. The pin could also be extended down to the raw subfloor.

The other stairbuilder writes that the starting post also rests on the screed and that a rubber bearing is placed between the screed and the starting post.

It is supposed to be a stairway from the basement to the ground floor without a wall stringer. The majority of what I have read so far is that stairs must be installed on the raw subfloor and that fixed parts must not be connected to a fleece screed. But why do the stairbuilders offer it so that the starting post of the stairs stands on the screed? What do you think about this, or is there a DIN regarding this? Many thanks

My feeling tells me that raw flooring is better. By the way, this is how it was done for us as well. At the start and end, screed was accordingly left out so that no drilling or tapping is necessary.

My feeling tells me that raw flooring is better.

I think so too, and the effort involved is certainly manageable. What surprises me, however, is that this is not planned by the staircase builders. Unless the point load on a railing-bearing staircase is not high. And if the newel post only rests on a rubber pad, the screed can still absorb movements.