How many tiers (or rows) of stone did Montresor have to lay in order to wall Fortunato up in the cave?

The answer to this is 11. There is a need to add a lot of rows because Montresor wanted to make sure that no one would be able to hear Fortunator’s cries for help. He knows that if someone hears the cries of Fortunato, that would already be the end of the revenge that he has planned. He still had other plans aside from this. He made sure that he will prepare the stones that he will use to build the wall.

He also made sure that he had the trowel ready because this will be his main reason for the revenge. He has also made it a point to study everything about Fortunato so that he will know what Fortunato’s weaknesses are. The things that he did cause him to finally get his revenge.