Top Soil for Turf and New Lawns
Find how much topsoil to put down before laying turf or sowing grass seed. See how much top dressing a lawn needs too.
Measure your project
Your answer
That weighs about 2.64 tonnes. We added 10% extra.
If you buy bags
If you buy bulk bags
Under new turf, Rolawn wants at least 100 mm of topsoil. Top dressing goes on just 3 mm deep.
What it costs
Topsoil: £109 per 500 litre bag, with VAT. That is the middle of only 3 bulk bag prices per m³ (Wickes, Rolawn, Oct 2026). Rolawn's 750 litre price had a short-term 6.5% surcharge on top. You pay for whole bags.
Quick answers
- Depth under a new lawn
- At least 100 mm (4 inches) of good topsoil, ideally 150 mm, says Rolawn.
- A 30 m² lawn, 100 mm deep
- About 3.3 m³ with 10% extra for settling. That is 7 bulk bags of 500 litres.
- Topsoil per m² of lawn
- Every m² of lawn takes 100 litres at 100 mm deep, or 150 litres at 150 mm.
- Top dressing
- 3 litres per m², about 3 mm deep (Rolawn). A 500 litre bag covers up to 167 m².
How to work it out
- Measure the lawn in metres. Multiply length by width for m².
- Pick a depth: 100 mm at least, 150 mm is better. Divide by 1,000 for metres.
- m² × depth in metres = m³ of topsoil. Times 1,000 gives litres.
- Add 10% for settling (Field Compost).
- Divide by 500 or 750 litres to count bulk bags. Round up.
30 m² × 0.1 m = 3 m³
3 × 1.1 = 3.3 m³ = 3,300 litres
3,300 ÷ 500 = 6.6 → 7 bulk bags
How much top soil for a lawn, by size
Find the row nearest your lawn.
| Lawn | m³, 100 mm | Bags | m³, 150 mm | Bags |
|---|---|---|---|---|
| 10 m² | 1 | 2 | 1.5 | 3 |
| 20 m² | 2 | 4 | 3 | 6 |
| 30 m² | 3 | 6 | 4.5 | 9 |
| 50 m² | 5 | 10 | 7.5 | 15 |
| 100 m² | 10 | 20 | 15 | 30 |
Nothing added for settling. Add 10–15% for that. A part bag is shown as a whole one.
Rolawn sells a turf and seeding topsoil for this job. Wickes had it at £142 for 500 litres, with VAT.
Do you need new topsoil, or just better soil?
Not every lawn needs bought topsoil. Rolawn's rule is at least 100 mm of good topsoil under the turf. Your own soil may already be good enough.
- Good soil, deep enough: dig or rotavate it. The RHS goes 20–25 cm deep. Rolawn sells a soil improver to mix into it.
- Thin, stony or full of rubble: bring in topsoil to reach 100–150 mm.
- Before laying: rake out stones over 6 mm. Two days before, Rolawn wets the soil 75 mm deep.
Lawn top dressing: how much to buy
To top dress a lawn, you spread a thin layer over grass that is already growing. Rolawn's is a loamy sand. It spreads 3 litres per m², about 3 mm deep, in spring or early autumn.
| Lawn | Litres | 500 L bags |
|---|---|---|
| 20 m² | 60 | 1 |
| 50 m² | 150 | 1 |
| 100 m² | 300 | 1 |
| 200 m² | 600 | 2 |
| 300 m² | 900 | 2 |
Rolawn's 500 litre bag costs £174.99 with VAT. Wickes had the same bag for £155 on sale (was £189). In the calculator, pick "Lawn top dressing".
Grass seed rates
- New lawn: Johnsons sows 35 g of seed per m². A 425 g pack then covers about 12 m².
- Overseeding: 25 g per m². The pack's printed cover of 20 m² is at about this rate.
- Firm the soil: the RHS treads it in several directions before sowing.
The RHS says to use the rate on your seed packet. Ours is from one seed maker.
Questions people ask
How much top soil do I need for turf?
Enough for 100 mm under the whole lawn, or 150 mm if you can. That is 100–150 litres per m². A 30 m² lawn needs 3–4.5 m³.
How deep does topsoil need to be to grow grass?
Rolawn says at least 100 mm thick, ideally 150 mm. Its guide gives lawns 100–150 mm.
Do I need topsoil before laying turf?
When laying turf, you need 100 mm of good topsoil, free of weeds. If your own soil is good to that depth, dig it over instead. Rolawn says poor soil makes turf decline.
Is topsoil needed for grass seed?
We found no UK grower or RHS rule on buying topsoil just for seed. Rolawn gives lawns 100–150 mm of topsoil. The RHS seed guide digs manure or compost into light soil instead.
How much topsoil for reseeding a lawn?
To reseed a thin lawn (overseeding), Johnsons sows 25 g of seed per m². We found no UK figure for soil on top.
How much top dressing do I need for a lawn?
Rolawn spreads 3 litres per m², about 3 mm deep. So 100 m² takes 300 litres, or one 500 litre bag.
Do you need to compact topsoil before laying turf?
No. Rolawn warns that packed-down soil drains badly and harms the turf. Tread over it 2 or 3 times to firm it instead.
Where our numbers come from
- Rolawn: topsoil depth for lawns and borders
- Rolawn Medallion turf spec: thickness, pallets, laying, aftercare
- Rolawn: preparing to lay turf
- RHS: how to lay turf
- RHS: how to sow a lawn from seed
- Johnsons lawn seed: sowing and overseeding rates
- Rolawn Lawn Topdressing: 3 litres per m²
- Topsoil settling and 70:30 mix: Field Compost
- Topsoil weight: Wickes 500 litre topsoil bag (about 400 kg)
- Topsoil bag prices: Wickes 25 L and 500 L bags
- Topsoil 25 L bag covers 0.5 m²: B&Q Verve
- Topsoil tested to BS 3882:2015: Rolawn Blended Loam
Made by BuildersCount. Last checked 4 Oct 2026.
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