I recently got approval to convert the back of my tandem garage into a habitable space. I was told that I require a firewall to separate the existing tandem garage in two. The floor of the garage is concrete. If I am building block work on this as a firewall, that is across the width of the garage, do I need to re I force the floor. If so how would this be done. Would I need to dig through the existing floor to lay a foundation,or is there some other method.