How to install the groundworks for an artificial grass lawn
By Gavin Hall
Professionally installed artificial grass groundworks
Having chosen a high quality artificial grass I will now walk you through how we install the groundworks for an artificial grass lawn
You have chosen the ideal artificial grass for your requirements. I will now explain how we install a perfectly level artificial grass lawn that drains well and is free from weeds. Our tried and tested installation method gives our customers a long lasting, great looking artificial grass lawn.
We assess the area and your requirements
We take a look at the area where you want to install the artificial grass and ask these questions:
What is the current drainage like?
If there is a boggy area which is prone to puddles then the irrigation will need to be improved. One way we do this is to dig a pit 2 to 3m² and fill it with rubble. These pits are often called soakaways and are fine for lawns with minor drainage problems. If the area has a major drainage issue a drainage expert will need to be brought in and install something like a large sunken tank.
Is there a severe slope in the garden that needs flattening out?
If this is the case I will position some 4″x 2″ Timbers (set in concrete) at the top of the slope which I will later fix the artificial grass to. This is done to prevent the grass from moving. Alternatively we add a small retaining edge i.e. railway sleepers so it can be slightly raised at one end to reduce the slope. Here I have written an indepth article on how we fit artificial grass on a slope.
Does the garden have a bad weed problem?
If the garden has a weed problem we use a Weedol Weed Killer to reduce the issue. If we do not eliminate the weeds at an early stage, weeds and real grass will eventually grow through the artificial grass. We have found that doing this reduces weeds by approximately 90%.
How much Type 1 aggregate will I need for the job?
As a rule of thumb the way I calculate how much Type 1 Aggregate I need: 7sqm = 1 tonne at 2 inches. If the lawn has particularly poor drainage I will double the depth of aggregate.
How much Granite dust will I need for the job?
To calculate how much Granite Dust I need: 14sqm = 1 tonne at 1 inch.
How much timber will I require for the perimeter of the artificial grass lawn?
I simply measure the distance around the perimeter with a measuring tape.
Clear the ground
To have nice clean, smooth foundations on which to lay your artificial grass I remove the turf, soil, vegetation and any large rocks or stones until I reach the natural sub base. This will generally require between 3-4 inches of excavation depending on the location. You will know when you have reached your substrate as the ground will be firm when you stand on it. We use a specialised turf lifter piece of machinery to speed this step up. We also use a mini digger / excavator if access allows. I dispose of all the old vegetation and stones etc in a skip. The skip is booked in advance and a suitable location for it is found.
Install a weed membrane
I don’t want grass and weeds growing through the artificial grass. To prevent this I add a thick Pro Tec Weed Membrane once I have cleared the soil. Note we always put the membrane on the bottom for these 4 main reasons:
- It is out of the way so doesn’t ruck up when pulling the grass across it
- It acts as a worm barrier to your base materials
- It stops the weeds at source
- If the lawn owners have dogs it is an absolute must for the weed membrane to be under the aggregate to prevent the urine trapping on the top.
There are other actions I take if the owners have dogs and want to make sure there is no urine odour issues in the summer months.
We take the membrane right to the edge of the lawn and use 40mm x 2.5mm Galvanised Nails to fix it in place.
Install the perimeter fixings
We lay 3″ x 2″ timber fixings around the perimeter of the area. To secure them I dig a trench a little wider than the timber. I then add concrete (a mix of ballast and cement) to the trench and set the timbers in it. I use plenty of concrete to make sure the timber will not move over time and I make sure it sits just below the level we wish the grass to be finished to, depending on the grass depth.
Prepare the sub-base
Add 2 to 4 inches of Mot Type1 aggregate
Just like in the preparation of roads professionally installed artificial grass requires a good sub-base so that the grass remains nice and flat. I start by using a 2-3 inch layer of Mot Type1 aggregate . I will only look to use chippings or Type 2 as an alternative if there is a drainage issue. These alternatives will be considered as there is less dust in the mix.
I then make sure the aggregate is evenly spread and compact it with the Belle Wacker Plate to just below the perimeter timbers.
Add 1 inch of Granite Dust
Next I add up to 1″ of Granite Dust which I rake across the surface of the Type 1 and then compact several times with a Wacker Plate. The more times you Wacker the Granite Dust the less chance there will be of sinkage in the lawn as the air gaps in the dust can potentially fill with water. Granite dust is a great product to use as it binds together beautifully when slightly damp. It then goes rock hard once dry but still allows water through. (We don’t use sharp sand as it doesn’t bond as well). We make sure enough granite dust is around the perimeter to make sure the edges don’t sink.
A quick self-promotion: I was the first person in the UK to use granite dust.
Screed the area
I now get down on my hands and knees and with a piece of Timber Screed (3′ x 2″ timber cut to approx 1.5m) the whole area to make it as smooth as possible. If the Granno is dry I periodically spray it with water to reduce dust. I work around the edge so the base is completely level with the timbers and drag the granite dust back making sure it is left in a nice hard but smooth shape. I generally go in semi circular motions. The reason I screed is because the artificial grass will mirror what is beneath it i.e. if you have lumpy groundworks your artificial lawn will be the same.
Here are a list of tools I use to prepare our groundworks (and links to where you can find my recommended products):
- A Wacker Plate
- Turf lifter Hire
- Mini Digger / Excavator
- Weed Killer
- Mot Type 1 aggregate
- Granite Dust
- Concrete mixer
- Cement for the concrete
- Ballast for the concrete
- A Screeding Tool (3″ x 2″ timber cut to 1.5 metres long)
- Bricklaying trowel
- 3″ x 2″ timbers
- 4″ x 2″ timbers (if laying on a slope)
- A Steel Rake
- Thick weed membrane
- 60mm x 2.5mm Nails for fixing membrane
- Spirit level
- Measuring tape
- Shovel for moving the aggregate
- Timber baton for pegging timbers in place
- Skip Hire
- Wheel barrow
- Bolster Chisel
- Club Hammer
- A Stiff Brush to clear up
Hopefully by reading how I install the groundworks for an artificial lawn you will see our attention to detail at this very important stage of laying artificial grass. I can’t stress enough the better the groundworks the better your artificial grass lawn will look.
In my next Blog post I will show you how we professionally fit the artificial grass on to the prepared groundworks.
Have further questions on how we install artificial grass please leave your comment below. Please make sure you have read other readers questions and my answers first as your question may have already been answered. You will also find some really useful information in the comments and answers below.