A question from a real amateur. I recently bought an apartment where we want to put up a couple of shelves on a concrete wall behind which the bathroom is located. What is on the other side of the wall in the bathroom is tiles consisting only of a towel heater. The bathroom also has underfloor heating. The wall consists of both lighter and "heavier" concrete, though a bit uncertain about how thick the wall is.
What should I consider to avoid doing something I'll regret?

If it is a concrete wall - is it even a problem? Just want to be on the safe side.
//Per