I have a garage (not attached to home) that I am am going to tear down and build a bigger one .The current one sits on a four inch slab 20x40.The new one is 30x50 and was wondering if I could pour new slabe on top of the old one. Plus I wanted only to use 35 foot of the old slab as I want to move the new unit a little more away from property line.location is south east Texas