Understanding Artificial Grass Excavation & Sub-Base Preparation
Proper ground preparation is the most important stage when installing artificial grass. A well-prepared artificial grass sub-base ensures your lawn remains level, drains correctly and lasts for many years without sinking or movement.
Before installing artificial grass, the existing turf and topsoil must be excavated and replaced with a suitable sub-base material. This creates a stable foundation that supports the artificial grass and prevents uneven surfaces over time.
Sub-Base Installation Options
There are typically two DIY installation options depending on the level of durability required:
- 25mm sub-base installation – quicker and more cost-effective
- 75mm sub-base installation – stronger, more durable and recommended for long-term performance
The tables below help estimate how much turf or soil you need to remove and how much sub-base material is required depending on the size of your garden area.
25mm Sub-Base Installation (Quick DIY Method)
A 25mm artificial grass sub-base is the simplest installation method and is often used for light-use garden areas where minimal excavation is preferred.
This method typically consists of:
- 25mm layer of granite dust or sharp sand
While this option is quicker and cheaper to install, it may not provide the same long-term durability as a deeper sub-base installation.
25mm Deep Excavation Ratio Examples
| Garden Area (m2) | Grass / Soil Waste (Ton) (25mm Deep) |
|---|---|
| 10 m2 | 0.4 ton |
| 30 m2 | 1.2 ton |
| 50 m2 | 2.0 ton |
| 70 m2 | 2.8 ton |
| 120 m2 | 4.8 ton |
25mm Deep Sub-Base Creation Ratio Examples
| Garden Area (m2) | Granite Dust or Sharp Sand (Ton) (25mm Deep) |
|---|---|
| 10 m2 | 0.5 ton |
| 30 m2 | 1.5 ton |
| 50 m2 | 2.5 ton |
| 70 m2 | 3.5 ton |
| 120 m2 | 6.0 ton |
75mm Sub-Base Installation (Recommended Method)
For a stronger and longer-lasting artificial grass installation, a 75mm sub-base is generally recommended.
This method consists of:
- 50mm primary base – Type 1 MOT, limestone, hardcore or crusher run
- 25mm secondary layer – granite dust or sharp sand
The deeper sub-base provides improved drainage and greater stability, making it ideal for gardens with regular foot traffic or heavier use.
75mm Deep Excavation Ratio Examples
| Garden Area (m2) | Grass / Soil Waste (Ton) (75mm Deep) |
|---|---|
| 10 m2 | 1.0 ton |
| 30 m2 | 3.0 ton |
| 50 m2 | 5.0 ton |
| 70 m2 | 7.0 ton |
| 120 m2 | 12.0 ton |
75mm Deep Sub-Base Creation Ratio Examples
| Garden Area (m2) | Primary Base - Limestone, Hardcore, Crusher Run, Type 1 MOT (Ton) (50mm Deep) | Granite Dust or Sharp Sand (Ton) (25mm Deep) |
|---|---|---|
| 10 m2 | 1.0 ton | 0.5 ton |
| 30 m2 | 3.0 ton | 1.5 ton |
| 50 m2 | 5.0 ton | 2.5 ton |
| 70 m2 | 7.0 ton | 3.5 ton |
| 120 m2 | 12.0 ton | 6.0 ton |
Important Installation Tip
Always finish your sub-base approximately 15mm below surrounding paving, patios or edging. This ensures the artificial grass backing remains hidden once the lawn is installed and provides a clean, professional finish.
Artificial Grass Measuring FAQs
For most artificial grass installations, excavation depth is typically 75mm below finished paving level. This allows space for a compacted sub-base and a smooth laying surface.
A common artificial grass sub-base consists of Type 1 MOT, limestone, crusher run or hardcore, topped with a 25mm layer of granite dust or sharp sand.
Yes. Installing a weed membrane between the soil and sub-base helps prevent weed growth while still allowing water to drain naturally.
Artificial grass should not be installed directly onto soil. The ground should first be excavated and replaced with a compacted sub-base to ensure stability and proper drainage.
In Summary
Artificial grass requires proper ground preparation before installation. Most gardens require excavation to around 75mm depth followed by a compacted sub-base of Type 1 MOT and a sharp sand or granite dust. layer.
Correct preparation ensures the lawn drains properly, remains level and performs well for many years.
Related Artificial Grass Installation Guides
Before preparing the ground for artificial grass, it is important to measure your garden correctly and choose the correct roll widths.
You may find these guides helpful: