Why Lawns Become Uneven
A perfectly flat lawn doesn't stay that way forever. Common causes of bumps and dips include:
- Soil settlement — especially on new-build sites where the ground wasn't properly compacted before turfing. See our soil preparation guide for how to avoid this from the start
- Mole or ant activity — mole hills compact the surrounding soil when flattened, leaving bumps
- Tree roots — surface roots push up over time, creating raised ridges
- Buried debris — rubble, old paths, or tree stumps decomposing underground and leaving hollows
- Wear patterns — heavy foot traffic compacts some areas more than others
- Poor original preparation — if the ground wasn't levelled properly before the turf went down, the unevenness only gets worse with time
Assessing How Bad It Is
Before you do anything, map out the problem. Lay a long straight edge (a 2m length of timber or a spirit level) across the lawn and look for gaps underneath. Move it across the entire area in different directions.
Mark high spots and low spots with small flags or sticks. This gives you a clear picture of whether you're dealing with minor undulation (top-dressing territory) or serious unevenness (lift-and-relay territory).
- Dips and bumps under 25mm: top-dressing
- Dips and bumps between 25mm and 50mm: heavy top-dressing over two or three applications
- Anything over 50mm: lift-and-relay
Method 1: Top-Dressing (Minor Unevenness)
Top-dressing is simply spreading a thin layer of soil mix over the lawn surface, letting the grass grow through it, and repeating until the surface is level.
What to Use
Mix together:
- 3 parts sharp sand
- 3 parts screened loam or topsoil
- 1 part garden compost
The mix should be dry enough to spread easily — not sticky or clumpy. You can buy pre-mixed top-dressing from garden centres, but making your own is cheaper for large areas.
How to Apply
- Mow the lawn slightly shorter than usual (not scalped — just a notch or two lower)
- Spread the mix over the low spots using a shovel, then work it into the grass with the back of a rake or a levelling lute
- Brush it in with a stiff broom so the grass tips are still visible — never bury the grass completely
- Apply no more than 15–20mm at a time
- Water lightly to help the mix settle
The grass will grow through within 2–3 weeks. If the area is still low, repeat the process a month later. It's slow but it works without disturbing the existing lawn.
When to Top-Dress
Spring (April–May) or early autumn (September) are ideal. The grass is growing actively enough to push through the new layer. Avoid summer — the dressing can bake hard in dry weather. Avoid winter — the grass is dormant and won't grow through.
Method 2: Lift and Relay (Major Unevenness)
For bumps or hollows deeper than 50mm, top-dressing alone won't cut it. You need to lift the turf, fix the soil level underneath, and relay it.
How to Do It
- Cut the turf. Use a half-moon edger or flat spade to cut the affected area into strips about 300mm wide. Slide the spade under each strip to lift it, keeping the turf about 40mm thick
- Roll back the strips. Carefully peel the turf back and lay it on a board or tarp. Keep it watered if you're working on a warm day — it dries out fast
- Adjust the soil level. For high spots, scrape away excess soil with a spade and rake smooth. For low spots, add topsoil and firm it down. Use a straight edge to check the level against the surrounding area
- Relay the turf. Roll the strips back into position, press them down firmly, and water thoroughly. Fill any joins with a sandy top-dressing mix
The turf should re-root within 2–3 weeks. Keep it watered as you would newly laid turf and avoid heavy foot traffic during this period.
Dealing with Tree Roots
Surface tree roots are a special case. You can't simply pile soil over them — the roots will push up again, and burying them too deeply can damage the tree.
Options:
- Raise the entire lawn level by 50–75mm with fresh topsoil, creating a new even surface above the roots. Only viable if you can maintain the new level at edges and paths
- Accept the contour and mow carefully around it. Raise your mower height in rooty areas to avoid scalping
- Remove the tree if it's small and the roots are destroying the lawn — but this is a last resort and may need council permission if the tree is protected
Preventing Future Unevenness
- Prepare the ground properly before laying turf — compact the soil with a roller or the "gardener's shuffle" to eliminate air pockets
- Deal with mole hills immediately — scrape off the loose soil and fill the hole with top-dressing rather than just flattening them
- Aerate annually to prevent differential compaction from foot traffic
- Avoid driving heavy equipment (wheelbarrows, mowers with full collection boxes) over wet ground — it creates ruts