Complaint stages for steel stringer stairs with a 2cm gap

Hello everyone,
we had a steel stringer staircase installed and were satisfied so far. When the construction steps were replaced with proper steps, there is now a 2 cm gap on each side.

That looks really stupid and everyone who has seen it so far agrees.

The stair builder says that this is okay and that it makes it easier to clean. He said that it complies with the DIN standard and that he doesn't care if anyone doesn't like it.

I haven't found anything on the internet about a DIN standard regarding the distance between the (steel) stringer and the step.

Can someone tell me if there are any regulations about how large the gap may be at most?
Thanks in advance!

I think he wants to trick you. Steel cheek stairs are of course also available flush and for cleaning that's a disaster. It naturally depends on what you looked at beforehand or what you ordered and whether it was specified that the steps should be flush.

I don't find it stupid/ugly though, it's just a matter of taste.

Best regards
Dirk Grafe

What was ordered?

we have never talked about a gap or anything like that. Based on the model of what the staircase will look like (as a computer-simulated model), the steps were included and even in the construction steps no gaps were visible. Therefore, we assumed that it would be the same with the actual steps.
Do we really have to accept this now?

I am not familiar with stairs, but I think the distance is normal for the stairs at my parents' house and at my home there is always a gap, probably also related to the fact that materials expand.

That's how we imagined it.