Lawn guide
Laying turf without topsoil: how deep should it be?
Turf needs a good layer of soil to root into. Sometimes the soil you already have is fine. Sometimes it needs topping up. Here's how to tell, and how deep it should be.
How much soil does turf need?
Grass roots do most of their work in the top 10 to 15 cm of soil. A lawn with that depth of reasonable soil underneath roots well, holds moisture in dry spells and drains after rain. Less than that, and it dries out quickly and struggles.
Is your existing soil good enough?
| What you find | Topsoil needed? |
|---|---|
| Dark, crumbly soil a spade deep | Usually not; loosen and level |
| Good soil but a few dips | A little, to fill the low spots |
| Thin soil over hard clay | Yes: around 10 cm or more |
| Stony or rubble-filled ground | Yes, after clearing the worst |
| Sand and stone (old artificial grass base) | Yes: the base comes out and soil goes back in |
| Builders' subsoil on a new build | Usually, after breaking up the compaction |
Laying onto existing soil
Where the soil is good, there's no need to buy in lots of topsoil. After lifting the old lawn, we break up the surface, pick out stones and roots, and rake it level and firm. That's often all a garden needs.
Types of topsoil
Topsoil varies a lot. Screened topsoil has been through a sieve to remove stones, roots and lumps, which makes it easy to level to a fine finish. Loam describes soil with a good balance of sand, silt and clay, so it drains well but holds moisture. A screened loam topsoil is ideal under turf.
Unscreened topsoil is cheaper but can be lumpy and stony, and subsoil sold as topsoil is pale, sticky and low in goodness. Avoid both under a new lawn.
Working out how much
Area × depth gives the volume. Our topsoil calculator does the sum and gives a rough weight. When we lay your lawn, any topsoil needed is listed on your quote.
Common questions
Can turf be laid straight onto clay?
It's better not to. Breaking up the clay surface and adding a layer of topsoil gives roots far more to work with.
How much topsoil for 50 m² at 10 cm?
5 m³, which is roughly 7 tonnes depending on how damp it is.