How Much Artificial Grass Do I Need? Roll, Sub-base and Sand (UK)
A lawn 5 × 4 m fits one strip of a 4 m wide roll: 5.25 m of roll with 5% extra for trimming (21 m² of grass). The base is 2.3 tonnes of MOT Type 1 (50 mm) and 0.8 tonnes of sharp sand (25 mm), with 22 m² of weed membrane and about 72 pins. The artificial grass calculator works out the roll and the base for your own lawn and chooses the way to lay the strips that wastes the least.
Grass and base for common lawn sizes
With a 5% trim allowance, a 50 mm sub-base and 25 mm of sharp sand:
| Lawn | Area | Grass: 4 m roll | Grass: 2 m roll | MOT Type 1 | Sharp sand |
|---|---|---|---|---|---|
| 3 × 2 m | 6 m² | 2.10 m of 4 m roll (0 joins) | 3.15 m of 2 m roll (0 joins) | 0.7 t | 0.3 t |
| 4 × 3 m | 12 m² | 3.15 m of 4 m roll (0 joins) | 6.30 m of 2 m roll (1 join) | 1.4 t | 0.5 t |
| 5 × 4 m | 20 m² | 5.25 m of 4 m roll (0 joins) | 10.50 m of 2 m roll (1 join) | 2.3 t | 0.8 t |
| 6 × 4.5 m | 27 m² | 9.45 m of 4 m roll (1 join) | 14.18 m of 2 m roll (2 joins) | 3.1 t | 1.1 t |
| 8 × 5 m | 40 m² | 10.50 m of 4 m roll (1 join) | 21.00 m of 2 m roll (3 joins) | 4.6 t | 1.7 t |
| 10 × 6 m | 60 m² | 18.90 m of 4 m roll (2 joins) | 31.50 m of 2 m roll (2 joins) | 6.9 t | 2.5 t |
| 12 × 8 m | 96 m² | 25.20 m of 4 m roll (1 join) | 50.40 m of 2 m roll (3 joins) | 11.1 t | 4.0 t |
Grass comes on rolls of a fixed width, so you buy a length, and a lawn that is a little wider than the roll costs a whole extra strip. If you can, choose the roll that fits the lawn in one strip.
Sub-base depth
MOT Type 1 for a 5 × 4 m lawn at each depth:
| Sub-base depth | MOT Type 1 for this lawn | Per square metre |
|---|---|---|
| 40 mm | 1.85 t | 0.09 t |
| 50 mm | 2.31 t | 0.12 t |
| 75 mm | 3.47 t | 0.17 t |
| 100 mm | 4.62 t | 0.23 t |
50 mm is typical for a garden lawn. Use 75 to 100 mm on soft or clay ground, or where there will be heavy use, and add drainage if water collects.
How to lay it
- Dig out the lawn to the depth of the sub-base, the sand and the grass: about 100 mm for a 50 mm base.
- Lay the weed membrane over the soil, then spread the MOT Type 1 in layers and compact each with a plate compactor, raking it to a slight fall for drainage.
- Spread the sharp sand, screed it level and compact it.
- Roll out the grass and leave it in the sun for a few hours so that it relaxes. Check that the pile runs the same way on every strip.
- Cut to the edges with a sharp knife, join the strips with tape and adhesive, and fix the edges with pins or nails along a timber edge.
- Brush the pile and add the infill if the maker recommends it.
Mistakes to avoid
- A base that is too thin or not compacted: it sinks and shows hollows.
- Joins where the pile points a different way, which show as a line.
- No edging, so the grass lifts at the edge. Fix the grass to a timber, concrete or paving edge.
- Forgetting drainage on clay soil. Artificial grass has holes in the backing, but the base must drain too.
- Buying the exact area: you need the trimming allowance as well.
For a real lawn, see the turf calculator. For the stone, see the gravel calculator. Estimates only: confirm the quantities with the supplier.
Frequently asked questions
How much artificial grass do I need?
The lawn area plus an allowance for trimming, ordered as a length of a 2 m or 4 m roll. A 5 × 4 m lawn needs 5.25 m of a 4 m roll (21 m²), and a 6 × 4.5 m lawn needs 9.45 m, with a join.
How much MOT Type 1 do I need for artificial grass?
A 50 mm sub-base takes about 0.12 tonnes per m², so 2.31 tonnes for a 5 × 4 m lawn. Soft ground needs 75 to 100 mm.
Do I need sand under artificial grass?
A 25 mm layer of sharp sand gives a smooth, level surface: 0.84 tonnes for this lawn. It sits on the MOT Type 1 sub-base, under the grass.
Do I need a weed membrane under artificial grass?
Yes. A membrane between the ground and the sub-base stops weeds and keeps the stone from sinking into soft soil.
How many joins will my artificial lawn have?
None if the lawn is as narrow as the roll (2 m or 4 m). A wider lawn needs a join for each extra strip, which should be tight and glued with joining tape.
More guides
Tools & materials for this project
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Estimates only. Quantities depend on your materials, site and supplier. Confirm important numbers before you order, and check the Building Regulations and any planning rules for anything structural or close to a boundary.