Why the settling happens
When we grind a stump, the wheel turns the wood into a pile of chip. That chip is loose. A cubic foot of solid stump becomes roughly three cubic feet of chip. If we leave the chip in the hole (the default, free plan), the hole reads as flat on grind day. Over the next twelve months two things happen: rain and gravity compact the chip, and the wood itself decomposes as fungi and soil bacteria eat it. Both processes pull the surface down.
How much and how fast
Typical yard settling for an eight inch grind at Korven job sites in the piedmont:
- Weeks 1 to 4: almost none. The chip is still fluffy.
- Months 1 to 3: half of the total drop. Rain compacts the top layer, foot traffic pushes it further, and the small chip pieces start to break down.
- Months 3 to 12: the remaining drop, slower but steady. By the twelve month mark most grind spots have settled one to three inches.
- Year 2 and beyond: negligible. What is left is close to soil.
Deeper grinds settle more. A twelve inch replant grind can drop three to four inches. An eighteen inch hardscape grind can drop five or six if the chip is left in.
The two ways to keep the lawn level
There are exactly two prevention strategies that work. Neither is complicated.
- Haul the chip and backfill with topsoil the same day. This is the only way to end grind day with a hole that will not settle. It is the priciest chip plan for a reason: it takes trailer time and topsoil cost. But the surface is level in the ideal case and stays level.
- Top-dress at three, six, and twelve months. Leave the chip in on grind day, then add a two to three inch layer of screened topsoil each time the spot drops noticeably. By month twelve the settling is done and the surface is at grade. This is cheaper and it is what most homeowners actually do.
What does not work: dumping a huge pile of topsoil on top of raw chip on day one. The pile hides the chip layer from decomposition but does not stop it, so the whole mound settles as one unit and you get a slow-motion sinkhole instead of a flat lawn.
When settling is a bigger deal than usual
If you are replanting a tree, laying a paver patio, pouring a footing, or seeding a fescue lawn on the grind spot, plan for the level lawn strategy from the start. See the seeding guide for the four step method that gets a level grass patch inside a season, and how deep should a stump be ground for why hardscape depth is eighteen inches and not eight.