We are having a contractor install a block foundation under an existing cabin which was previously on steel stilts. The steel was badly rusted and needed to go. The contractor dug a trench, poured some concrete and will start building up the block foundation underneath the cabin (which they raised up) soon. My question - how deep and wide should concrete be in order to place blocks on top of it? I'm traveling out of town on business, but have received a couple photos of the job in process. To me, the depth seems too shallow. (See attached photos). The property is in Southern Indiana, just North of Louisville, KY. Thanks.