We have a duplex that is constructed on SSM. Now we want to add pillars and extend the FF and add SF. Plot size is 40 x 40 , slant at the back end. Now the pillars are going to be on the compound wall and floors on cantilever.Is 3 pillars (18ft apart) sufficient on each side for 3 sides and 4th side SSM. what should be the rods size for each pillar?