06/05/2026
Cut and fill is what happens when someone cuts into a hillside to make a flat pad, then pushes the leftover dirt downslope to build on. When it is done right, with engineering and compaction testing, it holds. When it is not, that dirt is just sitting there, loosely packed, waiting to settle.
Before about 1980, nobody required compaction testing on residential fill. A lot of sloped lots in Oregon and Washington have old fill placed by a blade with zero testing. It looks like solid ground from the surface. It is not always.
On a Lane County property, a LiDAR analysis found a 1978 cut-and-fill bench that did not show up on satellite images or listing photos. The original mobile home sat on piers that flex with the ground. A new stick-built home with a poured concrete foundation does not flex. When old fill shifts unevenly under a foundation, the cracks start. A geotech study to find out how bad it is runs $3,000 to $8,000. And sometimes that study comes back with a worse answer than that. I have personally seen that answer come back.
Full case study in the first comment.