GLAREUM.NET›Chapter 10›Garden soil

10.7 Levelling an existing lawn

Evening out dips and bumps in a lawn that is already growing: which material to spread, how thin, and when to lift the turf instead.

Cross-section of a dip in a lawn being filled by topdressing: thin layers of material spread a few millimetres at a time, with the grass growing through each layer, until the surface reaches the target level. 1 Lawn soil match it, don't layer it 2 Topdressing max 12 mm per round 3 Grass tips at least half showing 4 Target level reached in several rounds
Cross-section of a dip being filled in thin rounds.

At a glance

Difficulty
1 of 4
Time
1–2 hours per round on 50 m²
Tools
Shovel, wheelbarrow, landscape rake or stiff broom, flat spade, straightedge or long board; core aerator for large areas
Parts
  1. 1  Lawn soil underneath
  2. 2  Thin topdressing
  3. 3  Grass growing through
  4. 4  Target level

What you need per m², one 6–12 mm round

MaterialKindTypeAmount
Topdressing Soil like your lawn's Screened, dry, free of stones, debris and weeds 6–12 l
or Sandy mix Only on lawns on sandy soil: 3 sandy loam : 6 sharp sand : 1 compost (RHS)
Topsoil Soil like your lawn's For lifting turf over a deep hollow (step 6) as needed

Which material?

Match the soil

The safe default is soil that matches the lawn's own. A different soil makes a layer that water and roots cross poorly. Check yours with the tests in 10.6.

Sand

Use sand, or the RHS sandy mix, only where the lawn grows on sandy soil. On clay or loam it makes a layer.

Compost

Sources disagree. Clemson calls compost the best topdressing for an average lawn's soil; Wisconsin advises using it cautiously, if at all, because composts vary and some seal the surface.

Not black dirt

An unmixed layer of black, peaty dirt stops water draining down. Avoid soil from farmland too: it can carry chemicals that kill grass.

Step by step

  1. 1

    Choose the method.

    Lay a long board across the dip. A shallow dip you fill from the top, a few millimetres at a time. A deep hollow or a bump you fix from underneath by lifting the turf (step 6).

    Straightedge across a dip
  2. 2

    Pick a material that matches.

    Use soil like the lawn's own. Use sand or a sandy mix only on a sandy lawn. Buy it screened and check it for stones, rubbish and weeds.

    Heap of screened topdressing
  3. 3

    Spread it thin and dry.

    Mow first. Spread no more than 6–12 mm at a time, and only when the material is fairly dry so it spreads evenly. At least half the height of the grass must still show.

    Thin layer with grass tips showing
  4. 4

    Work it in.

    Rake or brush it lightly so it sifts down between the blades. On large areas, run a core aerator over it to mix the new soil with the old.

    Brushing topdressing into the grass
  5. 5

    Repeat once the grass is through.

    Let the grass grow up through the layer before the next round. A low area can take several rounds over a few months. Work only while the grass is growing, not in heat, drought or dormancy.

    Dip almost at the target level
  6. 6

    Deep hollow or bump: lift the turf.

    Cut an H through the turf with a flat spade and fold the two flaps back. Fork the soil underneath and add topsoil to raise it or take soil out to lower it. Firm it level, lay the flaps back, brush a sandy topdressing into the cuts and water well.

    Turf flaps folded back from an H cut
Specifications
PartKindValueNote
Per round–6–12 mmWisconsin ¼–½ in; Clemson max ½ in.
Grass showing–≥ ½ leaf heightWisconsin.
MaterialDefaultlike the lawn soilWisconsin, Clemson, Penn State.
MaterialSandy lawns3 : 6 : 1Sandy loam : sharp sand : compost by volume (RHS). Sand only on sandy soil (Clemson).
Timing–active growthNot in heat, drought or dormancy (Wisconsin, Clemson). RHS: spring and autumn.

Amount

1 m² × 10 mm = 0.01 m³, or 10 litres. For a whole lawn of 100 m² at 6 mm, order about 0.6 m³.

Sand size

The RHS calls for sharp sand.

Sources

  1. University of Wisconsin Extension A3710, Lawn aeration and topdressing: topdressing smooths the surface; use a soil that matches the underlying soil to prevent layering; usually no more than 6–12 mm (¼–½ in); at least half of the leaf height visible; material fairly dry; core aerate to mix; build up low areas in several additions over months; only during active growth; compost cautiously if at all; an unmixed layer of black dirt stops drainage; avoid farmland soil; roll only moist soil, rollers compact
  2. Clemson University HGIC, Topdressing a home lawn: fill low spots with topsoil or sand where appropriate; topsoil should mirror the native soil; sand only where the native soil is sandy; no more than 12 mm (½ in) at a time; rake so it sifts between the blades; during active growth; compost is the best choice for the average lawn
  3. Royal Horticultural Society, Repairing lawns: level hollows and bumps by cutting an H, peeling back the turf, adding or removing topsoil, firming, replacing the turf and brushing sandy top-dressing into the cuts; home-made top-dressing 3 parts sandy loam, 6 parts sharp sand, 1 part compost; spring and autumn are the best times
  4. Penn State Extension, 8 steps to an easy field facelift: topdressing material should be chemically and physically very similar to the existing soil

Inches converted at 1 in = 25.4 mm and rounded. Imperial amounts are per 10 ft².

Section 10.7 Find these materials near you →

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