Everything You Need to Know About Installing a Sub-Base for an Artificial Lawn

Everything You Need to Know About Installing a Sub-Base for an Artificial Lawn


artificial grass for swimming pool surrounds

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?


Edging & Sub-Base

An Artificial Lawn Sub Base Consisting of 20mm Granite Chippings

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?


MOT Type 1

MOT Type 1

granite chippings

20mm Granite Chippings










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?


Vibrating Plate Compactor (whacker plate)

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?


hand tamp

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?


Granite Dust Laying Course

Granite Dust Laying Course

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?


steel edging for artificial grass

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?


NeoGrass Artificial Grass Foam Underlay Shockpad 1

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.

However, in those instances, rather than installing a sub-base and laying course, we generally recommend that you use either a 10mm or 20mm foam underlay.

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.





artificial grass by neograss

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.



44 Responses to “Everything You Need to Know About Installing a Sub-Base for an Artificial Lawn”

    • Neo Grass

      Hi Ian,
      Yes, Limestone Dust is fine to use on the top.
      You need to ensure that you have a minimum layer of 50mm of chippings but you also need to ensure that they are still able to be compacted down properly, so that they hold together and don’t just crumble away.
      Kind regards,

        • Neo Grass

          Hi Ray,
          A 40mm stone for the sub base would be too big. This is generally known as MOT Type 3.
          Ideally you need to use MOT Type 1, which sit at 10-15mm in size or if you have any drainage issues you can use a 20mm chipping.
          Kind regards,

  1. Bill Brooks

    Hello, I am replacing my existing 12 year old turf. One company is saying I need to also replace the existing sub-base and one is just filling in the low spots. What is the best option I should consider? Thank you

  2. Alex Nicholls

    Hi, thanks for the helpful advice above. I am compacting sub base on an area of my garden 12mx4m and don’t have a border at any of the sides. Is this ok or is it imperative to have a border?

    • Neo Grass

      Hi Alex,
      When constructing a sub base you would generally put it in a small sub frame all the way around in order to fix the grass to something.
      There are many types of materials available from a company called Everedge.
      Kind regards,

  3. I have existing paving slabs that i will putting the grass up to. I am so confused on how i will attach the grass to the edge do i need a frame? With all the hardcore are pins going to get in through it? I keep reading about glue but how would i glue the grass to a slab? Also having read about Kiln sand on top is there any worry with urine smells being trapped from dogs or ant issues? Sorry for long list! Many Thanks

  4. Andrew Paske

    Hi, I have a clay base which will have drainage issues, what would you recommend i put down before for sufficient drainage and in what order should I lay the layers before the grass, many thanks, Andy.

  5. Jonathan Roberts

    I’ve got a 14 sq meter circle in my garden. It’s full of gravel, what should I use on top of that before I lay artificial turf. Or should I get rid of it and use something else’s?

  6. Hi

    Having read your install guide.
    The one problem I’m having is one raised by Zoe previously. I’m going to be laying against a paved pathway that has been haunched and the the grass will slope away from it. How have I fix a timber frame upto the path with it having uneven concrete supporting the pathway. Hope this makes sense?

    • Neo Grass

      Hi Carl,
      Ideally, in this kind of circumstance, it would be better to apply a small concrete haunching and then glue the grass onto the haunching.
      Kind regards,

  7. James Figgett

    I’ve just stopped work on my garden halfway through and I’m unsure how best to proceed. The contractor has laid an mot sub base on to on old lawn without using a membrane. The depth varies due to the old lawn sloping but at one end is barely 25mm with soil visible at the very edge. Above that he had laid 50mm of un compacted sand before laying turf, the result is like walking on a beach, totally unacceptable. I am considering adding a fabric membrane onto the sand then adding enough limestone chippings to give around 20mm all over and compacting with a fine layer of grano on top. Before a final terram layer then turf. Would this be advisable or is it over the top? From what I’ve read I don’t think I want to just compact the sand?

  8. Lewis Shorter

    Please help I have had someone come and
    Lay my grass put it is like all the sand has washed away
    And there are lots of dips in the grass now why would this happen and now he what’s to put a timber frame down fill the gaps with shingle and sand and lay the grass on top of the timber frame ?

  9. Will a wacker plate compact it too much? As in will it affect the drainage? We currently have artifical grass laid on top of screed which is relatively ‘crumbly’ despite it being wacked. We have a really issue with drainage and smell with a dog using it as a toilet and are now looking at the best way of resurfacing underneath to have more effective drainage!

    • Neo Grass

      Hi Gary,
      Somebody else asked us about using Stone Dust yesterday but due to our lack of knowledge on the product we really can’t say if this would work the same as the granite or limestone dust.
      Kind regards,

  10. Hi, is it possible to overcompact the sub base and laying base? We had no drainage probs before we laid them (ie the soil drained fine). We followed all the instructions and have about 65mm type 1, 25mm Grano and a weed membrane. We whackered the soil and then each layer. Now we are mean to be laying membrane and grass, but have a couple of puddles. Tit is pretty level, so… could we have over-compacted? Thanks v much for advice

  11. Good afternoon I’m laying a sub base of 50mm limestone chippings and 25mm grano dust its two separate areas adding to 16 square meters, do you think this can be done with a hand tamper if I take my time and will the base still be good enough it’s foot and pet traffic. The garden is not that big and just laid patio and path and not sure about using a compactor there. Many thanks

    • Neo Grass

      Hi Kev,
      Ideally it would still be best to compact the area down properly with a whacker plate. We’re not sure if using a hand tamper would provide enough pressure for thorough compaction.
      Kind regards,

  12. I’m taking up and extending an area that already has artificial grass laid on top of grano dust, membrane and soil. It doesn’t seem to have a sub base and has drained well for some time (years). Do I need a sub base if the land appears to be firm and drain well already?

    • Hi Shane,
      We would always recommend laying a sub base not just for drainage purposes but also for stability but if you are confident that it has been fine as is up to now then that of course is your decision.
      Kind regards,

  13. Sarah Edwards

    I have a perfectly flat smooth ‘former’ driveway on a new build home, which is now part of our garden and won’t be used for cars. Do I need any sort of underlay at all as its really just for aesthetics and for the kids to run about on. Would a 20mm pile without a foam underlay work?
    Also I understand I should use some sort of adhesive on the edges/dotted around to seal it to the driveway but do you have any advice on what adhesive to use?

  14. Hi. I’m at the final part of laying my artificial grass after following your steps to the letter. You have been so helpful I really appreciate it. After laying the granite dust yesterday and making sure it was whacked down all over there has been heavy rain all night and I’m now looking at multiple puddles sitting on top. Is this expected? I’m hoping once the rain stops this water will just drain through. But obviously I’ll need to wait until it drys off completely before I lay the grass on top? Thanks for anymore advice.

    • Neo Grass

      Hi Andrew,
      As long as you didn’t go any deeper than 25mm of the Granite Dust then the water should still be able to seep away over a couple of hours.
      Sometimes if the size of the fines in the dust are too low, i.e at the bottom end of the scale as opposed to the top end then it can almost have a bit of a concrete effect.
      As you say, you ideally need to wait for some dry weather before you lay the grass.
      Kind regards,

  15. Hi I’m planning the installation of my artificial grass and was wondering if the sub base would be okay on top of top soil? My top soil is about 150mm thick on top of clay soil and I’d rather just excavate down about 75mm than 150mm to the clay sub-grade. I’d be using granite/limestone chippings and would also install a weed membrane between the soil and sub base. Any advice would be much appreciated, thank you!

      • Thanks for your quick reply Wendy. The soil doesn’t really suffer any drainage issues at the moment. The only concern I had was if the top soil would be too soft and end up sinking over time with the weight of the sub-base. Have you guys encountered any problems with laying in this way before?

        • Neo Grass

          Hi again Gary,
          We can’t really comment any further as it’s not really a standard sub base build up that is being done.
          You are right, in as much that top soil is never going to be as resilient as a sub base followed by a granite dust topping.
          Kind regards,

    • Neo Grass

      Hi Danny,
      It really depends on what size the gravel is. Ideally it needs to be 10-12mm in size, just like MOT Type 1 is.
      Also, i very much doubt whether gravel would compact down well enough with a whacker plate.
      Kind regards,

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