foundation cost question
I am in the contemplative stages of an addition to my small ranch home and have two areas I could logically build on to. One of these spots would be on grade, and the other would be building onto an area that is elevated about four feet (these would be the front and rear of my house respectively).
The original foundation is concrete block and I presume that the new addition would match this foundation type. Taking a theoretical eighteen by twenty-four foot addition space, can someone advise me on the approximate difference in costs between laying on grade versus three to four feet of built-up concrete block foundation? Is it huge or insignificant in the scheme of a remodel? Would this be a difference in a day of labor? A week? I am just clueless and unable to find this type of comparison on the Web to help me focus my design direction.
Thank you, folks.