The Importance of Adequate Compaction When Installing an Artificial Lawn
Installing artificial grass is a relatively straightforward process.
But, of course, to ensure success, it’s vitally important to ensure that each step of the installation process is completed correctly.
We have published several articles over the years to help both DIYers and professional installers to get the best results from their artificial lawn installations.
In our latest installation article, we’re taking a closer look at some of the reasons why it’s important to ensure that both the laying course and sub-base of your artificial lawn are adequately compacted.
Compaction is a key step and one that, if you don’t get it right, may result in the failure of your artificial lawn.
The groundworks are vital in any successful installation and we always say that you can have the best quality artificial grass money can buy, but if the installation isn’t completed correctly then you’re likely to have issues with your fake lawn in the years to come.
Experienced DIYers are certainly capable of carrying out their own artificial grass installation, but we do normally recommend using an experienced professional.
If this is the route you’re going take, then you may find it useful to search for your nearest NeoGrass approved installer.
They’ll be able to take care of everything from start to finish, so you don’t have to lift a finger. Of course, it’s likely to cost you more than a DIY installation, but it’s also likely that your artificial grass will prove to be a much better long-term investment, as a professional installation should perform better than a DIY installation.
Plus, it means you get to keep your precious spare time for relaxing, rather than slogging away out in the garden, and that, of course, is the whole idea of having fake grass installed in the first place.
But even if you’re considering using a professional, it’s still useful to know about the installation process, and the information in this article will give you good background knowledge about a key aspect of artificial grass installation.
When it comes to choosing the aggregates for your sub-base installation, you have two options available to you.
You can either choose MOT Type 1 or granite/limestone chippings.
In most circumstances we recommend that you use Type 1, compacted to a layer of between 50–100mm deep.
For the majority of garden installations, 50mm of Type 1 will create an adequate sub-base.
For heavy use, public areas, using a layer compacted to 100mm deep is recommended as it will have the capability of withstanding frequent heavy use.
Under some circumstances, choosing a sub-base comprising granite or limestone chippings is recommended.
The great thing about these chippings is that they are a ‘washed aggregate’.
This means that they do not contain any fines. An aggregate diameter of between 10mm and 20mm works best.
If you are a pet owner, then we highly recommend that you choose this type of aggregate. This is because it is a permeable sub-base that will allow liquids, in this case, urine, to drain through the turf then through the sub-base without leaving behind any nasty odours.
Another example of when we would recommend this permeable sub-base is if your garden has drainage issues. If there are areas of your lawn that are boggy for a large part of the year, then use granite or limestone chippings.
Likewise, if your artificial grass will be receiving large amounts of surface water run-off, from a large patio, for example, then again, go with a permeable sub-base.
However, if you have neither a pet nor drainage issues in your garden, using Type 1 is the best way to go.
Laying Course Aggregates
For the laying course, we highly recommend 25mm of granite or limestone dust.
Whether you use granite or limestone doesn’t matter, just use whatever is locally available. In some parts of the country you’ll find it easier to obtain one type of aggregate over the other.
Contrary to popular belief, whatever you do use, we recommend that you avoid using sharp sand.
In the early days of artificial grass installation, many contractors would put down a layer of compacted sharp sand prior to laying the fake turf.
This works fine for block paving, but it’s not quite the same with artificial grass.
The major difference is that artificial grass allows up to 52 litres of water to drain through its perforated backing per square metre, per minute.
This means that during a heavy downpour, large amounts of water will be passing through your fake turf, and then through the layer of sharp sand beneath. Over time, the water will begin to erode parts of the sharp sand laying course and you may start to notice undulations appearing in the surface of your lawn. This is caused by movement in the laying course.
Sharp sand also tends to lose some of its compaction over time.
However, as granite dust is a far coarser material, it will hold its compaction and allow water to pass through without any movement of the laying course.
Always Use a Vibrating Plate Compactor, Where Possible
Both the sub-base and the laying course require adequate compaction to prevent dips and undulations from appearing in your artificial lawn.
To do this, you’ll need a vibrating plate compactor. Every professional contractor should own one of these, but for DIYers, they can easily be obtained from your local tool hire shop.
For areas that you can’t reach with a plate compactor, such as when installing artificial grass ribbons, using a hand tamp is the next best thing.
Never Compact in Layers of More Than 50mm
We recommend that your sub-base material is compacted to a minimum of 80% of its compaction capacity.
A typical vibrating plate compactor will only achieve 80% compaction when the sub-base material is no more than 50mm thick. Therefore, you should only ever compact 50mm of aggregate at a time. So, in the case of a 100mm sub-base layer, you’ll want to compact this in two separate layers to achieve the desired result.
Compact Laying Course Material When Wet
Water also has an important role to play in compaction of the sub-base material.
After importing and levelling your sub-base material, be it type 1, chippings, or the granite/limestone dust laying course, we recommended saturating the aggregate.
By doing so, you’ll further aid the compaction of the material.
Of course, there is a fine line between not enough water and too much.
You’ll want to ensure that the water penetrates the entire depth of the sub-base material from top to bottom, but you’ll want to avoid flooding the surface.
If the base is too wet, you’ll find that your plate compactor sinks too deep into surface. If this is case, allow the aggregate to dry out.
Also, pay attention to any material that sticks to the bottom of the plate compactor. You may need to regularly clean the underside of the plate to avoid leaving grooves in the finished surface.
Always Re-Compact the Sub-Base After Repairs
At some point in the future, there may be a need to lift a part of your artificial lawn for various reasons.
For example, you may at some point need to install new or repair existing utilities, such as water, gas or electric pipes, or storm drains, that may run under your fake turf.
It’s normally a relatively straightforward process to lift part of your lawn, if necessary, but, of course, it’s vitally important that any disturbed sub-base material is sufficiently compacted to avoid settlement in the future.
Again, this is best achieved with a vibrating plate compactor or a hand tamp for those hard to reach areas.
Compacting Large Areas of Sub-Base
When compacting large areas of sub-material, such as on a large installation for public use, rather than using a vibrating plate compactor, you’ll achieve far better results with a BOMAG or vibratory drum roller.
Not only will this speed up the process, but it will also achieve a greater level of compaction than a push along compactor would.
Don’t Attempt to Compact Your Sub-Base on Waterlogged Earth
Of course, the first step in a typical artificial grass installation is to excavate the existing turf to expose the sub-grade, or soil, ready for the sub-base installation.
Before you begin importing sub-base material, the sub-grade, or earth, should not be saturated or waterlogged. If it is, it will severely hamper the compaction of the aggregate.
If you are faced with a saturated sub-grade, you should allow it to dry out before spreading the sub-base material. Failure to do so could mean inadequate compaction and issues will include an uneven sub-base further down the line.
The groundworks are a crucial part of an artificial lawn installation, whether it’s a small front garden lawn or a sprawling picnic area in a popular theme park.
It really is the ley to a long-lasting, high-performing fake lawn.
The aim of this article was to educate both installers and consumers about the importance of proper compaction of the sub-base material.
Hopefully you’ll now have a better understanding of the best practices to follow to avoid any potential future issues with the failure of your fake lawn.
If you have any questions or would like further clarification of anything in this article, then leave us a comment below.