Most people shopping for artificial grass spend a lot of time comparing turf products but almost no time thinking about what goes beneath them. That is a costly mistake. The layers you put under artificial grass determine how well it drains, how long it lasts, and whether it stays level and firm after the first rainy season hits.

In Miami, where the ground is dense, the rain is heavy, and summer heat pushes surface temperatures past 100 degrees, getting the base layers right is not optional. This guide breaks down exactly what to put under artificial turf, layer by layer, so your installation holds up for 15 to 20 years without sinking, smelling, or shifting.

Why What Goes Under Artificial Grass Matters So Much

Artificial turf itself is durable. Quality products can last two decades with proper care. But turf is only as good as what supports it from below.

A weak or poorly planned base causes:

Uneven surfaces that develop bumps, dips, and soft spots within months
Drainage failure that leads to standing water, mold, and odor under the turf
Weed breakthrough along seams and edges that lifts and distorts the lawn
Turf movement that causes wrinkles, loose edges, and visible seaming

Miami’s specific conditions make this even more important. The soil here is often a mix of clay, sand, and limestone, which drains inconsistently. Add heavy summer rainfall and a shallow water table in many neighborhoods, and you quickly see why skipping or rushing the base layers is never worth it.

The Complete List of What to Put Under Artificial Grass

Here is every layer that belongs beneath a properly installed artificial lawn, from the ground up.

1. Excavated and Cleared Native Soil

Before you add anything, the existing ground needs to be cleared and excavated.

Remove all existing grass, weeds, roots, and organic debris to a depth of 3 to 4 inches below your desired finished surface level. This depth accounts for your base material and the height of the turf pile.

In Miami, aggressive weeds like torpedo grass and dollar weed have deep root systems. Any roots left behind will eventually push up through your base and cause surface irregularities. Take the time to remove organic material thoroughly before moving to the next layer.

After excavating, check whether the soil surface has any low spots or slopes that direct water toward your home’s foundation. Correct these now by adding or removing soil as needed.

2. Herbicide Treatment Directly on Soil

Once the area is excavated, apply a non-selective herbicide directly to the exposed soil surface.

This step does not get enough attention, but in South Florida’s climate, it is essential. Miami’s warm, wet conditions allow weeds to germinate and grow year-round. A pre-emergent herbicide applied at this stage kills seeds and root fragments before they can push through your base layers and cause problems later.

Allow the herbicide to work for 48 to 72 hours before laying any materials on top.

3. Crushed Aggregate Base Layer (Most Critical Layer)

This is the single most important component of what goes under artificial turf.

A 3-inch compacted layer of crushed miscellaneous base (CMB), also called road base or crushed aggregate, forms the structural foundation of your artificial lawn. Some installers in South Florida also use decomposed granite, which compacts well and drains consistently.

Why CMB and not plain fill dirt or sand?

Plain dirt compresses unevenly and retains moisture. Sand alone is too loose and shifts under foot traffic. Crushed aggregate locks together when compacted, creating a firm, stable, load-bearing surface that also allows water to pass through freely.

How to apply it correctly:

Spread the aggregate evenly across the excavated area using a rake
Aim for a consistent depth of 3 inches throughout
Use a plate compactor to compact the material in overlapping passes
Check for level across the entire surface with a long straightedge or laser level
Add a slight slope (roughly 1 inch of drop per 8 feet) away from your home if drainage is a concern

In areas with extremely poor drainage or high water tables, some Miami installers add a layer of drainage matting beneath the aggregate for additional water management. This is worth discussing with your contractor if your yard holds water after heavy rains.

4. Weed Barrier Landscape Fabric

Once your base is compacted and level, lay a permeable weed barrier across the entire surface.

Landscape fabric serves two purposes: it blocks weed seeds in the base material from germinating and migrating upward, and it provides a clean separation layer between your aggregate base and the turf backing.

Key points for Miami installations:

Use a permeable, commercial-grade landscape fabric, not a solid plastic sheeting
Solid plastic traps moisture and creates the exact conditions that promote mold and bacteria growth in humid climates
Overlap all seams by a minimum of 6 inches
Secure the fabric with landscape staples every 12 to 18 inches, including along all seams and edges

Cheap or thin weed fabric breaks down within a few years in South Florida’s UV-intense environment. Invest in a heavier-grade product rated for outdoor and high-temperature conditions.

5. Artificial Turf Backing with Built-In Drainage Holes

The turf itself has a role in the drainage system. Quality artificial grass products feature a perforated or urethane-coated backing with drainage holes punched throughout at regular intervals, typically every few inches.

When choosing your turf product, check the drainage rate specification. A good artificial turf for Miami’s rainfall patterns should drain at a minimum of 30 inches of water per hour per square yard. Some premium products drain at 100 inches per hour or more.

Turf with inadequate drainage holes or a solid backing will turn your beautifully prepared base into a retention pond every time it rains. Always verify drainage specs before purchasing your turf rolls.

6. Sand or Infill Material

Infill is the final layer that goes into and on top of the artificial grass rather than beneath it, but it plays a structural role that makes it part of the complete base system.

What do you put under artificial turf for infill? Nothing. Infill sits between the turf blades, not beneath the backing. But it is critical for three reasons:

It weighs the turf flat and prevents shifting
It supports upright blade posture so the lawn looks natural and full
It helps regulate surface temperature and aids drainage through the backing

Types of infill used in Miami:

Silica sand is the most common and cost-effective option for residential lawns
Crumb rubber provides extra cushioning for play areas and athletic surfaces
Zeolite or antimicrobial infill is recommended for pet areas because it absorbs ammonia and controls odors in warm, humid conditions
Durafill or acrylic-coated sand helps reduce surface heat, which matters in Miami where turf can get very hot on summer afternoons

Apply infill with a drop spreader or by hand and work it between the blades using a power broom or stiff brush. Brush against the grain of the fibers to push infill down while encouraging blades to stand upright.

What NOT to Put Under Artificial Grass

Knowing what to avoid is just as important as knowing the right materials.

Do not use solid plastic sheeting. It blocks drainage completely and traps moisture beneath the turf, creating an environment for mold, bacteria, and odor, especially in Miami’s humidity.

Do not skip the aggregate base. Laying turf directly on native soil, even compacted soil, results in uneven surfaces and poor drainage. The base layer is not optional.

Do not use organic mulch or wood chips as a base. These materials decompose over time, causing the turf surface to sink and develop soft spots. They also attract insects and pests.

Do not use regular topsoil as fill. Topsoil is too soft and retains too much moisture. It will not compact properly and will shift under foot traffic.

Layer-by-Layer Summary

Here is a quick reference for everything that belongs beneath your artificial lawn from bottom to top:

Excavated native soil (cleared to 3 to 4 inches depth)
Herbicide treatment applied to soil surface
3-inch compacted crushed aggregate base (CMB or decomposed granite)
Permeable weed barrier landscape fabric
Artificial turf with perforated drainage backing
Sand or specialty infill worked between the turf blades

Each layer serves a specific function. Remove any one of them and you weaken the entire system.

Get the Foundation Right With Grass Masters Exteriors

Now that you know what to put under artificial grass, you can see why the base preparation matters as much as the turf itself. Every layer has a job, and every shortcut shows up eventually as a problem you will have to fix.

At Grass Masters Exteriors, our Miami installation teams have laid the base for over 1,000,000 square feet of synthetic turf since 2019. We use the right materials, the right compaction, and the right drainage setup for South Florida’s specific conditions, so your lawn looks and performs exactly the way it should for years to come.

Frequently Asked Questions

What goes under artificial grass in a rainy climate like Miami? A compacted crushed aggregate base topped with permeable weed barrier fabric is essential. These two layers work together to drain rainwater quickly and prevent pooling beneath the turf. Pair them with a high-drainage-rate turf backing for best results.

Do I need landscape fabric under artificial turf? Yes. Landscape fabric keeps weeds from pushing up through your base material and into the turf over time. In Miami’s year-round growing season, skipping this layer leads to weeds appearing at seams and edges within the first year.

Can I put sand directly under artificial grass instead of an aggregate base? Sand alone is too loose and does not compact firmly enough to serve as a structural base. It shifts under foot traffic and drains inconsistently. Crushed aggregate is the correct base material. A thin layer of sand can be added on top of the aggregate before laying the weed barrier in some installations, but it does not replace the compacted base.

What do you put under artificial turf for pets in Miami? All the same layers apply, with one addition: use a zeolite or antimicrobial infill material on top of the turf to control pet odors. Miami’s heat amplifies odor problems, making this upgrade well worth the cost for homes with dogs.

What to Put Under Artificial Grass Before Installing It in Miami, FL