many houses down here're blt on pedestals,,, sounds as if the bldr didn't have his elevations nutz-on so had to shim,,, 10t hydraulic jack & some oak shims'll work fine when you get 'round to it.
you've got the advantage of actually SEEING this marvelous dwelling, tho,,, may need a carrier beam to spread the weight.
OSB ? ? ?,,, oy VEY ! ! !