Understanding Excavation & Sub-Base Quantities

There are two ways of installing DIY artificial grass - with a single 25mm sub-base or double 75mm sub-base. During the planning stages of your garden makeover, you need to establish which option you are going for, so you know how much old grass and topsoil you need to remove. Your options are:

25mm deep sub-base consisting of: (Quicker, Easier, Cheaper)

  • 25mm granite dust or sharp sand.

Or Alternatively:

75mm deep sub-base consisting of: (Better Durability & Longevity)

  • 5Omm deep limestone, hardcore, crusher run or type 1 MOT
  • 25mm deep granite dust or sharp sand

It is essential to understand the advantages and disadvantages of both options before attempting your DIY project. We provide further information below, but fundamentally the deeper the sub-base, the longer the installation will hold up to foot traffic and prolonged daily use.

IMPORTANT: Always finish your sub-base approximately 10mm below any path or paving level to ensure no artificial backing materials are visible once installed.

25mm deep sub-base

You'll find granite dust and sharp sand at your local builder's merchants or DIY store, and they are both relatively inexpensive. Granite dust tends to be a little more expensive than sharp sand, but we believe it is the better option due to its superior drainage properties. However, many UK landscaping companies still use sharp sand for their installations, so it is down to personal preference.

If installing your artificial lawn with a single sub-base, we recommend excavating the required depth before applying a layer of good quality weed membrane. Next add 25mm of granite dust or sharp sand, and level it out using a wacker plate or compactor before installing your artificial grass.

The benefit of this type of installation is that it is quick, cheap, and requires less excavation work. The tables below illustrate how much turf/soil you should excavate and how much sub-base material you need for a single 25mm sub-base artificial grass 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 Deep Sub-Base

Primary Base - 50mm Deep Limestone, Hardcore, Crusher Run or Type 1 MOT

All the sub-base materials we mention in this section are ideal for creating a primary base for your artificial lawn. While not all materials are available nationwide, you’ll find at Ieast one of the above at your local builder’s merchants or DIY store.

Once you have excavated the required depth, apply a layer of good quality weed membrane before adding 50mm of your chosen primary sub-base material. Level with a wacker plate or compactor plate.

Secondary Base - Granite Dust or Sharp Sand

Add a 25mm deep layer of granite dust or sharp sand. Compact again to create a smooth, flat surface. You could apply a second layer of good quality weed membrane at this stage; however, this is optional.

Installing artificial grass with a double sub-base could help you achieve better results and make your investment last longer. The tables below illustrate how much turf/soil you should excavate and how much sub-base material you need for a double sub-base artificial grass installation.

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