My wife and I are about to start building a modular house with a crawl space. The foundation will stand with one long side on existing ground and the other long side on filled ground (about a 2m height difference). Initially, the plan was to fill, vibrate, and be content, but now the head contractor suggests that I should install concrete pillars from the "original" ground to the foundation slab instead of just filling up and laying the foundation like that. This, of course, means an additional cost. What I'm wondering is if this is a good idea or if it would suffice to just fill? Alternatively, should we dig down where the ground is highest to the same level as where it is lowest and fill under the entire house? Ideas and thoughts are greatly appreciated! 
Sincerely, Ronnie
Sincerely, Ronnie