[Griff]

I wonder if we're blending terminology a little sloppily here. Soil usually refers to the upper layer of earth which is full of organic matter and is unsuitable for construction. I would tend to agree with tw though that they probably built on fill rather than virgin subsoil. I wonder if there are other things to consider, like improperly installed drains and whether the footer is below the frost-line? I don't know anything about mudjacking, keep us posted.