I think if you want a serious response you need to give us a lot more information.
Second, what does the staircase look like? Is it straight? Does it make a right angle turn and have a landing? Does it make a 180 degree turn? Is it a spiral stair case? Is it flat steel or is it comprised of a collection of steel bars? How about a photo?
Third were is it? It doesn't do any good to make it into a speaker if it is not in a position where you can listen to it. For example, if it is in a narrow hallway, it is not going to be that easy to listen too.
Forth, are you willing to enclose the staircase?
Fifth, you speak of 'my building' rather than 'my home'. What kind of building is it? If it is some type of apartment or condo complex, and the staircase is in a common area, your neighbors might not take to kindly to the idea. Also, do you actually own this staircase?
Sixth, even if you can and do do this, is it really to your advantage? Is it really more flexible and versatile than easily moved floorstanding tower speakers?
As the old saying goes, The devil is in the details.