i want to add a 7 x 4 bathroom onto the side of my sister room the wall is made with 6" brick

what i want to do is dig a 12" foundation then drill about 7 3/4" hole about 10" in the flooring of her room from the outside then insert 3/4" steel in them to make a bedding to cast the flooring which will be about 10" thick then lay block onto to build the bathroom wall is it safe to do it that way will the steel in the bathroom seperate from the rest of the house can anyone give me any idea how you make such a addition