Soil, stone and materials
How much topsoil do I need? Grades, depths and tonnes
Topsoil is sold by the bag, the bulk bag or the tonne, and it is easy to order far too little or far too much. The sum itself is simple: area, times depth, times a weight per cubic metre. The judgement is in the depth.
By the Gardens North East teamPublished , 3 min read
Step one: the area
Measure the area in square metres, splitting awkward shapes into rectangles, triangles and circles. Our turf measuring guide walks through the method; it works the same way for soil.
Measure each job separately if the depths differ. A new lawn and a new border need very different amounts per square metre.
Step two: the depth
Common recommendations for finished depth of good topsoil. Where you already have decent soil underneath, you need less.
| Job | Typical depth | In metres for the sum |
|---|---|---|
| Top-dressing an existing lawn | A thin layer, around 10 to 20 mm | 0.01 to 0.02 |
| New lawn on poor or thin ground | 100 to 150 mm | 0.10 to 0.15 |
| New flower or shrub border | 300 mm or more | 0.30 |
| Raised bed | The full depth of the bed | Height of the bed |
| Levelling a dip | The depth of the dip at its deepest, averaged across it | Measured |
Step three: cubic metres to tonnes
Area multiplied by depth gives the volume in cubic metres. Bulk topsoil is usually sold by weight, so you need to convert. Suppliers commonly work on somewhere between about 1.3 and 1.6 tonnes per cubic metre, depending on how moist the soil is and how finely it has been screened. Ask your supplier which figure they use.
Loose soil also settles once it is spread and firmed, so allow a little extra, often around 10%.
Grades and screening
Topsoil in the UK is commonly described against BS 3882, the British Standard that sets out grades such as multipurpose topsoil. Screened soil has been passed through a mesh to remove stones and lumps; a finer screen gives a smoother surface for lawns and seed beds.
Ask what the soil is, where it comes from and whether it has been screened. If you are making a lawn, a screened, weed-free topsoil saves hours of raking. For heavy North East clay, mixing a layer of good topsoil into the surface helps new roots more than piling a thin skim on top of compacted subsoil.
Bags or bulk?
For top-dressing or a few small beds, bagged soil from a garden centre is often enough. Once a job runs into several tonnes, such as levelling a whole new-build garden or building a large raised area, a bulk load delivered by lorry is usually simpler. Check where the load can be tipped: on the drive, on a sheet, or further in if access allows. A tipper needs firm ground and clear headroom.
Community groups and allotment societies sometimes club together for a bulk load to share between plots. If you are improving an allotment, ask your association first.
For smaller amounts, such as topping up borders or a few square metres of lawn, Brunswick Turf sells topsoil alongside its turf. For bigger jobs, Newcastle Topsoil delivers screened topsoil tipped in loads of five tonnes or more and quotes for your site.
Questions readers ask
How many bags make a tonne?
It depends on the bag size and how wet the soil is. Check the weight printed on the bag, and remember that a bulk bag sold as about a tonne may not be exactly that.
Can I lay turf straight onto subsoil?
It will struggle. Grass roots need a layer of proper topsoil. On new-build plots, check what is under the surface before you turf.
Should I mix compost into topsoil?
For borders, mixing in well-rotted organic matter helps, especially on clay. For a new lawn, a good screened topsoil on its own is usually fine.
Ready to order?
For a few bags or a small top-up, Brunswick Turf sells topsoil alongside its turf. For projects measured in tonnes, Newcastle Topsoil delivers bulk loads from five tonnes, quoted for your site.
Turf supply and installation for gardens across the North East.
Bulk topsoil for bigger projects, from five tonnes per load, quoted for your site.
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