I think you have to ask the one who offers it to you... And finding someone who pours a echte exposed concrete staircase will definitely not be easy. That’s why my tip: ask your architect where he would buy a "stink-normal" prefabricated staircase, go there and look at the quality. Pouring a straight staircase with visually appealing surface quality is no rocket science for a professional, I claim. Ours certainly looked great.