I top up infill maybe once a year across the whole yard, a normal amount each time. One side of the lawn, though — the side that runs slightly downhill toward the fence — kept needing noticeably more than everywhere else, and by the time I actually measured it, that section had visibly less infill depth than the rest of the yard despite getting the same top-ups. What tipped me off first wasn’t a visual difference so much as how it felt underfoot near the fence line — the blades stood up less there, and the ground had a harder, more compacted feel than the same walk a few feet uphill. It took months of not paying close attention before I finally knelt down and checked, pushing a finger through the pile to the backing near the fence and comparing that against a level spot near the patio with similar foot traffic. The difference came out to something close to a quarter inch — enough to feel the backing under my fingers in a way I couldn’t anywhere else in the yard.
Where Infill Actually Goes
Infill doesn’t just vanish — it moves, and it moves for a few specific reasons that aren’t always obvious from looking at the surface. On any section with even a mild slope, infill gradually migrates downhill over time as rain and regular foot traffic nudge individual granules a little further down with each pass; it doesn’t wash away in one dramatic event, it just slowly redistributes toward the low point. Infill also gets pulled out mechanically — stuck to shoes, pulled up in a stiff-bristle brush used the wrong direction, or kicked out of the pile during active play in one concentrated spot. A slope adds a directional bias on top of all of that normal loss, which is exactly why one section of our yard needed so much more than the rest: it wasn’t losing infill differently, it was just also losing it downhill toward a specific edge instead of staying distributed evenly.
There’s a mechanical piece to this that’s easy to miss because it looks identical to ordinary wear from a distance. Every footstep or hose rinse nudges a granule slightly downhill of where it started; on flat ground that cancels out roughly evenly in every direction, so depth holds steady. On a slope, gravity breaks that symmetry every time, so the net drift is always toward the low point, even in stretches with no rain. Sprinkler runoff made it worse in our case specifically — the irrigation zone covering that side of the yard runs longer than the others because it’s also watering a flower bed along the fence, so that strip of turf gets more water contact than anywhere else in the lawn.
Fixing the Uneven Distribution, Not Just Adding More
- Checked the infill depth at several points down the slope to confirm it really was migrating rather than just being lost outright — the fence-line low point had noticeably more infill piled against it than a flat section would ever accumulate on its own.
- Redistributed some of that excess back up the slope by hand rather than buying entirely new material for the thin spots.
- Topped up the remaining shortfall with fresh infill, worked in with a drop spreader for an even depth rather than dumping it in one spot and brushing it out.
- Added a bit more infill specifically at the top of the slope going forward, anticipating that some of it will continue migrating down over time rather than trying to stop the migration outright.
The reason I redistributed existing infill by hand instead of dumping a fresh bag into the thin spots comes down to cost as much as anything — buying new material to refill a section that’s just relocated, not gone, means paying twice for infill that’s still sitting twenty feet away doing nothing useful. It doesn’t fix anything long-term either; a full top-up on a slope with no other change just hands gravity a fresh supply to keep working with. If your low point happens to be a drain instead of a fence line, the same redistribution still works, but check the drain grate itself for buried infill sitting directly on top of it — that’s material actively blocking drainage, worth clearing separately from the general redistribution.
Managing Infill on a Sloped Section
If any part of your yard has a real grade to it, expect infill to migrate downhill gradually no matter how well it was installed, and plan on checking depth at the low point more often than you check the flat parts of the lawn. Slightly over-filling the top of a slope during the original install, rather than filling it evenly with the rest of the yard, gets ahead of the migration instead of chasing it every year.
Migration or a Settling Base — How to Tell Which One You Have
Before assuming migration is the whole story, it’s worth ruling out a compacting or settling base underneath, since the surface symptom — a lower, softer spot — can look almost the same from a few feet away. The difference is in the shape of it: migration leaves a shallow, gradual depth change that follows the slope evenly across a wide strip, while a settling base creates a localized dip you can feel underfoot that doesn’t line up with the yard’s overall grade at all. Pressing a flat hand on the turf and comparing how much give there is against a spot you know is fine is usually enough to tell the two apart without pulling anything up — a soft dip that doesn’t track the slope is a base problem, not an infill problem, and redistributing infill on top of it won’t fix what’s underneath.
When I called a local turf maintenance outfit for an unrelated quote once, they mentioned that rebalancing infill on a sloped section is usually folded into a standard seasonal visit, priced by the trip rather than by the bag. Since redoing ours, that fence-line section has held close to a full year without a repeat, in line with the once-a-year top-up schedule I already run everywhere else — and doing the work in milder weather rather than peak summer heat made it noticeably less miserable, since infill handles easier when it isn’t scorching from a full day of direct sun.