Per pass
≤ 1/4 in
Cornell, compost topdressing
1,000 sq ft at 1/4 in
0.8 yd³
of topdressing mix
When
Active growth
so grass grows through
A bumpy lawn scalps on the high spots, holds water in the low ones and makes every striping pass look wavy. The fix depends on how deep the problem goes. Shallow dips come up with thin layers of topdressing spread over a season; deep ones need the turf lifted and the soil filled underneath. Either way, find the cause first, or the bumps come back.
Find the Cause Before You Fill
A bump or dip is a symptom. Fill it without fixing what made it and it comes back. Walk the lawn after rain, when low spots hold water and soft spots give underfoot.
| Cause | What you see | Fix first |
|---|---|---|
| Settling over a trench or old stump | A long dip along a utility line, irrigation run or where a tree came out | Lift the turf, fill with soil, firm it and lay the turf back |
| Moles, voles or digging animals | Raised ridges or soft mounds that move over weeks | Deal with the animal first; leveling before that is wasted work |
| Grub damage | Spongy turf that peels back like carpet, often with skunks or birds digging | Treat grubs, then repair and seed the damaged area |
| Leaking irrigation | A soft, wet dip near a head or line that never dries out | Repair the leak before adding any soil |
| Heavy traffic or equipment | Ruts from mowers, vehicles or wet-weather foot traffic | Topdress shallow ruts; core aerate compacted paths first |
| Uneven grading at install | Gentle waves across the whole lawn | Repeated light topdressing, or regrade and replant for big swings |
Grubs are the one to rule out early; the grub guide shows how to check a square foot of turf. Wet dips that never dry are a drainage problem, covered in landscape drainage solutions.
Shallow Dips: Level by Topdressing
Topdressing raises the surface a little at a time while the grass grows up through it. Cornell's sports-field guidance applies compost no more than 1/4 in per application and describes light passes of roughly 1/8–3/8 in, done when the turf is actively growing. The same guide notes that light applications level minor depressions; for anything deeper, lift and fill instead.
- 1
Mow short (for your grass)
Mow at the low end of the normal height for the grass so the mix reaches the soil. Don't scalp it.
- 2
Dethatch if needed
A thick thatch layer keeps the mix sitting on top. Clear it first if it is over about half an inch.
- 3
Spread a thin layer
Shovel the mix into the low area and spread it with a leveling rake or the back of a landscape rake.
- 4
Work it into the canopy
Drag or brush the mix down between the blades until the grass tips show through everywhere.
- 5
Water lightly
Settle the mix into the turf and wash it off the leaf blades.
- 6
Wait, then repeat
Let the grass grow through before the next pass. Several thin passes beat one thick one.
Match the mix to your soil
Cornell warns that topdressing with a very different particle size causes layering, which disrupts drainage and rooting. Use your existing soil or one similar in texture, and keep using the same material on later passes. Pure sand over clay is the classic mistake.
How Much Mix to Order
Cornell's table puts 1/4 in over 1,000 sq ft at about 0.8 cubic yards and 1/2 in at about 1.5. Measure only the uneven area, not the whole lawn. For bulk soil by the yard, the mulch and topsoil calculator prices the order.
Topdressing mix needed
Area of the bumpy section, depth per pass and how many passes you plan.
Depth per pass
Per pass
0.31 yd³
8.3 cu ft
All passes
0.93 yd³
25.0 cu ft
Formula: sq ft × depth (in) ÷ 12 ÷ 27 = cubic yards.
Deeper Dips: Lift, Fill and Relay
When a dip is too deep for the grass to grow through a few thin layers, move the turf instead of burying it. Cut an H or a cross through the low area with a flat spade, peel the turf back, add soil underneath and firm it with your foot, then lay the turf back so it sits flush with the surrounding lawn. Water it in like new sod. High spots work the same way in reverse: lift the turf, scrape soil out, relay.
A whole lawn of waves is a regrading job. Strip or kill the turf, grade the soil with a box blade or by hand, and replant. That is the moment to weigh sod against seed, and to test the soil pH while it is bare.
When to Level
Level while the grass is actively growing so it can push up through each layer: spring and early fall for cool-season lawns, late spring through summer for warm-season lawns. Pairing it with core aeration works well, since the mix falls into the holes, and fall leveling on a cool-season lawn can roll straight into overseeding.
Common Questions
Can I just use sand to level my lawn?
Only if the lawn already grows on sandy soil. Cornell's guidance warns that a topdressing with a very different particle size from the soil underneath creates layers that disrupt drainage and rooting. On clay or loam, use a screened soil that matches what is there, or a soil-compost blend.
Will rolling the lawn flatten the bumps?
Rolling presses down soft ridges for a while but does not move soil from high spots to low ones, and a heavy roller on wet ground compacts the soil the roots need. Use it, if at all, lightly on moist soil to settle new turf, not as a leveling method.
How many topdressing passes will it take?
Divide the depth of the dip by what you add per pass. A one-inch dip at about 1/4 inch per pass is four passes, each one after the grass has grown back through the last. Plan on a season, not a weekend.
Should I level before or after overseeding?
Level first. Seed can go down right after the final pass, and the topdressing mix makes a good seedbed. Seeding first and then burying the seed under a thick layer wastes it.