Every building starts with a foundation — sometimes stilts, sometimes slabs, sometimes basements, and some are built on good solid earth. A house built on sand sinks and demands many posts dug to keep it. You dig and dig until you have made a solid place so that as the sands shift, the house will not sink too far. Houses settle after a time. Sometimes that is why there is a tiny difference in a floor once so flat a ball wouldn’t roll. The “roll test” is to find if the house h