Close the gap between the stairs and the wall

Hi

What is the best way to close a gap between the stairs and the wall?
Problems:
1. The gap is not very small - between 1.5 and 2.5 cm
2. The distance varies

Regards
Rico

Silicone ??? Photos would be great you

So definitely stuff rock wool into the gap and then it depends on the covering whether it covers the gap. I assume concrete stairs? Actually send photos and show what you want to do later

Yes, sorry - I noticed afterwards that important information is missing. So wooden stairs inside. For silicone or acrylic that would be quite wide, right?!

I would have the stair builder make a thin cover strip in the same design and glue it on. Actually, something like that should be part of the stair installation anyway.

Yes, cover strips... the carpenters' favorite parts...
Best regards
Gabriele