What’s the Best Sub-Base for Artificial Grass? We Tested Them All…

Thinking about getting an artificial lawn? We don’t blame you – It’s become hugely popular among new homeowners.

The reason is quite simple: With artificial grass, your lawn looks great year-round!

Selecting the style of grass and pile heights are important considerations when choosing your new artificial lawn. Nowadays, there are plenty of styles and options to suit your needs and tastes.

But while the look of your lawn is important, what goes on under the surface is just as critical to the successful installation and long-term service life of your artificial grass.

The sub-base layer of your new lawn plays a significant role in its service, life, wear-and-tear, and maintenance over the years. If you don’t get a proper sub-base installation, you’re going to end up regretting it in a few months.

That’s why it’s so important to get it right from the start.

What Is the Sub-Base for Artificial Grass?

The sub-base is the layer directly under the artificial grass. It’s mostly a sand and gravel mix, but some installations might require the use of asphalt, concrete, or wood – depending on the application and conditions.

So, why do you need to install a sub-base for your lawn?

It’s simple: The base provides the structure for the grass. Without it, your lawn will sink and crease as people and animals move around on the surface.

Think of it like installing a carpet. It’s critical to have a proper base underneath the surface layer to ensure you have a solid foundation to step on!

In addition, without a base material for artificial grass, you might experience poor drainage and water will pool on the surface.

In other words, a good artificial grass sub-base material provides your lawn with a perfect mix of stability and good drainage, as well as long-term durability and resilience.

Can I Lay Artificial Grass Directly On Soil?

The answer is definitely NOT! Here’s why:

Soil is an expansive base material. This means it naturally expands and contracts depending on how wet it is.

If you install your artificial grass directly on the sand, you will start to see a lot of wrinkles and pits in your lawn due to the expansion/contraction effect.

Wet soil will result in soft spots and divots in the lawn, causing the grass to lift away from the soil and create air pockets.

In turn, these air pockets provide the perfect breeding conditions for mold and bacteria!

A sub-base replaces the traditional soil base with a stable, non-expansive layer. The result is an effective and long-lasting installation that lasts for decades!

What Sub-Base To Use For Artificial Grass?

There are different types of artificial grass sub-base materials. Choose the right option to meet your needs.

For instance, installing a sub-base for a putting green is a vastly different task than fitting a backyard lawn.

There are three main types of sub-base materials available for your artificial grass lawn.

Our expert team has tested and installed all three over the years. Let’s discuss each of the options in detail:

1. Crushed Miscellaneous Base (CMB)

Typically used in landscaping applications, crushed miscellaneous base (CMB) is an aggregate material featuring gravel, sand, asphalt, and concrete.

CMB mostly comes from the offset of concrete or asphalt recycling, consisting of gravel and sand mixtures of up to 3/4″ in diameter.

It compacts well, giving you a solid foundation, and it’s a more affordable material than Decomposed Granite (DG).

The downside to CMB is that it’s challenging to source, and it takes more effort to smooth down.

The non-porous nature of this material also means drainage will be slower, which might be an issue if you live in an area with heavy rainfall, or you need your pets’ urine to drain away quickly.

CMB remains the default choice for most home installations. However, if you’re worried about drainage, we would recommend decomposed granite instead.

2. Class II Road Base

Class II Road Base is the most expensive option on our list. It’s somewhat similar to CMB, but comes with stringent testing and quality checks by the manufacturer.

We usually use this material for advanced, large-scale installations for commercial and sporting applications, such as football pitches and putting greens.

However, due to the overall cost, we do not feel the Class II road base is necessary for the domestic needs of your backyard.

3. Decomposed Granite/Limestone Chippings

Decomposed Granite (DG) and Limestone Chippings offer you the best option for your backyard. However, it does come at a higher cost.

DG is smoother than CMB, but it doesn’t compact as well. Despite this, you end up with a material that drains well, and that’s a top priority for the long-term health of your lawn.

The smoother surface also means it is ideal for putting greens. But if you’re installing a laying course on top (see the next section), it may not matter in the end.

These sub-bases are made up of fragments that weather and fall away from the main rock body (either granite or limestone, and sometimes a mixture of both).

Today, manufacturers run large granite rocks through a DG process to produce the end product. This ensures the fragments are uniform in size.

Both decomposed granite and limestone are porous, allowing optimal drainage of your artificial grass.

For all these reasons, decomposed granite and limestone chippings is the overall best choice for a sub-base. But if budget is an issue, CMB will suffice for most domestic applications.

When it comes to how much sub-base you should use for artificial grass, we generally recommend a depth of 2″ to 4″ (50mm–100mm), with a thicker layer for heavier use.

Your Laying Course: Granite Dust vs Sharp Sand

The laying course is also a fundamental part of installing your artificial grass.

This is the last layer of aggregate material installed directly under the artificial lawn and on top of the sub-base.

The purpose of your laying course is to provide a smooth, level and flat surface to lay your synthetic grass.

When laying your course, we recommend using granite dust or limestone, otherwise known as “Grano” (short for ‘granolithic’). The individual grano dust particles are around 6mm in diameter and installs at a depth of 1-inch.

Why You Should Avoid Sharp Sand

Many installers use sharp sand for artificial grass as the laying course, but that’s a huge mistake! Here’s why:

Artificial grass features perforations in its latex backing, allowing water to drain from the surface. Your artificial lawn comes with drainage of up to 10 to 12-gallons a minute.

Because it’s so loose, this drainage will eventually wash away the sharp sand. You’ll notice it by the ridges and dips you see appearing on your lawn.

Also, a big problem with sharp sand is that it moves underfoot. If your pets and kids spend any time playing on the lawn, the foot traffic will loosen the sharp sand over time, and cause dips and creases in the material.

Sharp sand also encourages ant infestations. The ants will excavate the soil to build nests underneath your lawn, and this disruption will cause lifting and unevenness that only gets worse over time.

Granite and Limestone Dust

Grano is the more expensive option for your sub-base. However, it’s the best material for your artificial lawn, providing a long service life, and saving you a lot of trouble and money in the long run.

It packs together well but remains permeable, allowing for optimal drainage. At the same time, it’s durable and resilient to water flow, and will not move around in harsh weather conditions.

Manufacturers typically pack and sell grano to contractors in bulk. These bags can weigh nearly a ton, so make sure you get proper estimates from your contractor regarding your installation.

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