Everything You Need to Know About Installing a Sub-Base for an Artificial Lawn
It is vital to ensure that artificial grass is properly installed to ensure that it can fulfil its purpose, i.e. to provide a stunning low-maintenance lawn that can be used by the whole family and their pets all year round.
Remember, you can’t just lay artificial turf on top of the real turf you want to replace, and it is absolutely not possible to install fake grass directly on top of earth or soil.
You’ll first need to excavate your existing lawn, and then level and compact two layers of aggregates, known as the sub-base and the laying course. Without them, your artificial lawn will not look or perform as it should.
We’re frequently asked a variety of questions regarding the process of installing a sub-base and laying course for an artificial lawn.
We’ve already covered everything you need to know about installing a laying course in a previous article, and today we are focusing on sub-base installation.
Here, we’ve pulled together a list of your most burning questions, complete with the answers you’ve been looking for.
Our aim is to give you the knowledge you’ll need to complete your own artificial lawn installation to the highest standard.
And, as long as you follow the advice in this article, you’ll have no problem in installing a stunning artificial lawn that not only looks amazing, but also performs well, and continues to do so for years to come.
Let’s start with explaining exactly what we mean by the ‘sub-base’.
What is a sub-base?
Within the artificial grass industry, the ‘sub-base’ is known as the layer of aggregates that are installed on top of the subgrade, or earth, prior to the installation of the laying course.
Do I need to install a weed membrane underneath the sub-base?
Yes, it is highly recommended that a weed membrane is placed directly underneath the sub-base, both to prevent weed growth and to separate the aggregates from the subgrade. If the sub-base is laid down without this barrier in place, the aggregates can mix with the earth, which can, in turn, result in settlement or sinking in the finished lawn.
Why should I install a sub-base?
The sub-base material is the foundation of an artificial grass installation; it is what will give your artificial lawn structural stability.
A solid, well-compacted sub-base is crucial in providing sufficient strength to allow foot traffic and items of furniture to be placed upon the artificial lawn.
What should the sub-base consist of?
The sub-base material should comprise either MOT Type 1, or 20mm stone chippings – either granite or limestone.
Which is better to use: Type 1 or stone chippings?
Generally, MOT Type 1 provides a slightly stronger base than stone chippings. This is because of the increased level of compaction, due to the amount of ‘fines’, or small particles, found within the makeup of Type 1.
However, although MOT Type 1 will allow a certain amount of water to drain through it, it is technically a non-porous aggregate. If your garden has drainage issues or if you have a dog or pet who will be using the lawn, we highly recommend that you install a sub-base consisting of granite or limestone chippings, as that will allow liquids to quickly drain from the surface of your lawn, through to the sub-grade.
For domestic applications, granite or limestone chippings will provide a more than adequate sub-base layer that will be amply strong enough to cope with everyday family life.
When using a permeable sub-base, which is better: granite or limestone chippings?
There is no difference in performance between granite or limestone chippings, so use whichever form of aggregate is easiest and/or cheapest to source in your local area.
Depending upon your locality in the UK, you may find it easier to source one form of aggregate over the other. As neither performance nor quality are an issue, your choice can be based on price and/or convenience.
What depth should the sub-base be installed to?
This depends on usage. For domestic applications, we recommend a minimum depth of 50mm (2”).
For commercial or public areas, such as artificial grass at schools and playgrounds, we recommend installing a sub-base of between 75mm to 100mm (3” to 4”).
Do you always need to install a sub-base?
If you are installing artificial grass to a sound, existing surface, such as concrete, decking or paving, then it would not be necessary, as the existing surface will provide sufficient structural support.
If you are replacing a real grass lawn, then you must always install a sub-base. You cannot lay artificial grass directly on to earth.
How much aggregate will I need for the sub-base?
MOT Type 1 and granite or limestone chippings are typically supplied in ‘bulk bags’, or ‘ton bags’, as they are also known.
Contrary to their name, ton bags typically weigh around 850kg, rather than a ton, so please ask your supplier for the approximate weight of the bulk bags prior to purchasing, to ensure you order the correct quantities.
For larger areas, you may find it more financially beneficial to have a loose load of aggregates tipped on site.
To help you calculate how much you need, enter the total square meterage of your lawn area in the calculator, below.
Where can I get hold of Type 1, or granite or limestone chippings?
You can normally buy them from your local aggregate supplier, builders’ merchant or DIY store.
Either granite or limestone chippings can sometimes be a little more difficult to source, and as there is no difference in performance between them, use whichever is easiest/cheapest to source in your local area.
How do I level the sub-base material?
The laying course is levelled to the required depth, using a rake, across the entire lawn area, and then thoroughly compacted.
How do I compact the sub-base material?
The sub-base should be compacted using a vibrating plate compactor, which can be hired from your local tool hire shop.
To ensure adequate compaction, guide the plate compactor both up and down, and from side to side, across the entire surface of your lawn area.
For further information on compaction, please see ‘The Importance of Adequate Compaction When Installing an Artificial Lawn’.
How do I compact the sub-base material in small areas, such as between two stepping stones, where a vibrating plate compactor can’t fit?
For areas that the plate compactor will not reach, such as between stepping stones, narrow strips of turf or tight corners, we recommend that you compact the aggregates using a hand tamper.
Should there be anything installed on top of the sub-base?
Yes. A laying course consisting of 25mm (1”) of granite or limestone dust, sometimes referred to as ‘grano’, should be installed on top of the sub-base material, followed by an optional second layer of weed membrane, prior to laying the turf.
What should I use to retain the sub-base material?
When installing artificial grass, it is very important to have an edge restraint in place.
The edge restraint will retain the aggregates and prevent them from collapsing at the sides of your lawn.
The edging may also provide something to secure the perimeter of your lawn to.
For further information on the types of edging system you can use, and how to secure the perimeter of your artificial lawn, please see ‘6 Types of Edging System for Artificial Grass’.
I am installing a foam shockpad underlay; do I still need to install a sub-base?
Yes, a sub-base is still required to provide a strong foundation to the artificial lawn. We recommend that you follow the standard installation procedures and lay your foam underlay on top of the laying course material.
Foam underlays should not be laid directly onto the sub-base, as the larger stones found within the sub-base material could potentially puncture the underlay.
Can I install a sub-base over an existing surface, such as paving slabs?
It is possible to install artificial grass to existing surfaces such as concrete, paving slabs, block paving and decking.
The foam underlay will provide a sufficiently smooth surface to lay the grass on to. The foam will both provide a soft feel underfoot and cover up any undulations in the underlying surface – for example, the ridges in decking – which, without the presence of the foam, would be visible through the finished artificial lawn.
Installing an adequate sub-base is a vital part of the artificial grass installation process.
It is what gives an artificial lawn its strength. You can have the best artificial grass, but without a strong foundation, it will not perform as well or look as good as it should.
That said, installing a solid sub-base needn’t be difficult and, after reading this article, we hope you are now armed with the knowledge you need to undertake your installation.
However, if there is anything we haven’t covered, then please leave your questions in the comments section below and we’ll do our best to answer any further questions you may have.
If you would prefer to use the services of a professional to install your artificial lawn, then we’d highly recommend that you contact your nearest NeoGrass Approved Installer, who’ll be more than happy to conduct a free site visit, advise upon the best installation practices and provide you with a free written quotation
Don’t forget, you can also request your free samples of the NeoGrass range of artificial turf by clicking here.