Why Gardens Become Uneven
Gardens develop bumps and hollows over time for several reasons: tree roots pushing up, settlement after building work, poor drainage creating soft spots, or simply years of uneven wear. An uneven lawn is more than an eyesore — it makes mowing difficult, creates waterlogged patches, and can be a trip hazard.
Topsoil is the most common material for levelling, but the technique matters. Dump soil on a bumpy lawn and you'll bury the grass, create new low spots, and end up with a worse surface than you started with.
Assess What You're Working With
Before ordering topsoil, walk the garden and understand the scale of the problem.
Minor Unevenness (Under 25mm)
If the lawn is generally level but has shallow dips and bumps, you don't need bulk topsoil. A top-dressing mix (typically 70% sharp sand, 20% loam, 10% compost) spread thinly across the surface is the standard approach. Apply 5-10mm at a time, brush it into the grass with a stiff broom, and let the lawn grow through. Repeat every few months until level.
Moderate Hollows (25-75mm Deep)
This is where screened topsoil works well. You can fill hollows without removing the existing turf, provided the grass is healthy and the layer isn't thick enough to smother it entirely. Grass can grow through up to about 25mm of top-dressing in one application — deeper than that and you need to work in stages or lift the turf.
Significant Unevenness (Over 75mm)
For deeper hollows or a generally uneven surface, you'll need to lift the existing turf (or accept reseeding), fill and level with topsoil, compact lightly, then re-lay turf or sow seed. This is a bigger job but gives the best results.
Step-by-Step: Levelling with Topsoil
1. Mark Out the Area
Use pegs and string lines to establish your target level. Place pegs at regular intervals (every 2-3 metres) and run taut string between them at the desired finished height. Use a spirit level on the string to ensure it's true.
For a lawn, a very slight gradient away from the house (roughly 1:80 to 1:100) helps drainage. Dead flat can lead to standing water.
2. Prepare the Ground
For shallow fills, mow the existing grass as short as possible and scarify to open up the surface.
For deeper fills, lift the turf with a spade or turf cutter and set it aside (it can be re-laid if used within 24-48 hours and kept moist). Fork over the exposed soil to break up any compaction — new topsoil sitting on compacted ground creates a drainage barrier.
3. Add the Topsoil
Use screened topsoil — stone-free and fine enough to create a smooth surface. Tip it into the low areas and rake roughly level.
For large areas, calculate your volume carefully. A hollow that looks like it needs "a bit of soil" often takes more than you expect.
4. Level and Compact
Use a long straight-edge (a 2-3 metre length of timber works perfectly) to screed the topsoil level with your string lines. Pull it across the surface, adding or removing soil as needed.
Once level, firm the soil gently. Walk over it with short, overlapping steps (called "heeling in") or use a light roller. Don't over-compact — you want the soil firm enough that it won't settle dramatically, but loose enough for roots to penetrate. The depth of your topsoil layer matters for root establishment.
5. Final Check
After compacting, check levels again. The soil will have dropped slightly. Top up any low spots, re-level, and firm again. Water the area lightly — this reveals any remaining low spots where water pools.
6. Turf or Seed
Once you're happy with the levels, either re-lay the lifted turf, lay new turf, or sow grass seed. If seeding, lightly rake the surface to create a seed bed and sow at the recommended rate (typically 25-35g per square metre for a utility lawn).
How Much Topsoil Do You Need?
A useful rule of thumb: 1 cubic metre of topsoil covers 20 square metres at 50mm depth, or 10 square metres at 100mm depth.
For a typical garden levelling project on a 50m² lawn with average hollows of 50-75mm, expect to need 2.5-4 cubic metres — that's 4-7 bulk bags.
Order 10% extra for settlement and wastage. Leftover screened topsoil is never a problem — spread it thinly on borders or use it for potting.
Common Mistakes
- Burying the grass too deep. Grass can grow through 10-20mm of top-dressing. Any deeper and you need to lift the turf first or accept reseeding
- Using unscreened soil. Stones, roots, and clods in the fill create new bumps once settled
- Not compacting. Uncompacted topsoil settles over months, often unevenly, undoing your work
- Ignoring drainage. If the garden is uneven because of poor drainage, adding topsoil without fixing the drainage just creates a different shape of waterlogged garden. See our guide on fixing waterlogged soil
- Working in wet conditions. Wet soil is impossible to level accurately and compacts unevenly
When to Call a Professional
If the garden has significant level changes (more than 150mm), involves retaining walls or drainage work, or covers a large area, a landscaper with a mini-digger will do in a day what takes a week by hand. Budget around £200-£400 per day for a landscaper with a machine, plus the cost of topsoil.