What to Put Under Artificial Grass for Drainage

Solid Ground Outdoor
Apr 23
4 min read

TLDR;

To ensure proper drainage under artificial grass, use a well-compacted sub-base made of crushed stone or gravel, topped with a geotextile fabric to prevent soil contamination, and consider additional drainage layers like perforated pipes or drainage panels if necessary. These components help water flow efficiently, prevent pooling, and extend the life of your synthetic turf.

Why Proper Drainage Matters for Artificial Grass

Without proper drainage, artificial grass becomes more than just an aesthetic concern—it turns into a functional liability. You’ll face:

Water pooling: leading to muddy messes, especially after rain.
Odor issues: stagnant water under turf can produce unpleasant smells.
Sub-base erosion: weak foundation causes sinking or uneven surfaces.
Weed growth: poor drainage often accelerates weed intrusion.

Many believe artificial grass doesn’t need drainage because it's synthetic—but that’s far from the truth. Just like natural lawns, artificial turf requires a system that allows water to flow through and away efficiently to prevent damage.

What Goes Under Artificial Turf for Drainage?

Crushed Stone or Gravel

A compacted base of 3/4-inch crushed stone or angular gravel is one of the most critical layers under synthetic turf.

Promotes excellent water flow.
Provides a firm, stable base for the turf.
Resists movement and settling over time.

Recommended depth: 3–4 inches minimum, adjusted based on soil type and drainage needs.

Decomposed Granite (DG)

Offers a smooth finish and compacts tightly.
Allows moderate drainage but can retain water in heavy rain.
Best used in conjunction with gravel or as a top-off layer.

Caution: On clay soil, DG can hold too much moisture.

Class II Road Base / Crushed Miscellaneous Base (CMB)

A blend of crushed rock and fine particles.
Often used in road and driveway construction.
Ideal for high-traffic areas or load-bearing installations.

Downside: Can limit drainage slightly due to fine particles unless properly compacted and layered with permeable materials.

Sand (Used with Caution)

Fine sand can clog drainage systems over time.
Retains water and compacts poorly under weight.
Avoid as a standalone base layer but can be used as infill or a minor leveling layer if paired with better-draining sub-bases.

Sub-Base for Synthetic Turf: Building the Right Foundation

Your sub-base does the heavy lifting when it comes to drainage. Here's the most effective way to build one:

Remove 3–6 inches of topsoil or sod.
Fill with permeable aggregate like crushed granite or gravel.
Compact the base with a vibratory plate compactor.
Ensure the surface has a slight slope (1–2%) for surface runoff.

For added durability and drainage, a 2-layer system using gravel and Class II base may be best.

Advanced Artificial Grass Drainage System Options

Geotextile Fabric or Membrane

Installed between the base and the turf, this material:

Prevents soil from mixing with the sub-base.
Allows water to pass through.
Adds weed control benefits.

Always use a non-woven, permeable geotextile for best results.

Drainage Grids or Panels

These modular solutions are excellent for:

Balconies or rooftops.
Clay-heavy soils with poor drainage.
Areas where traditional excavation is not possible.

Benefits:

Quick water dispersal.
Easy installation.
Structural support.

Perforated Drainage Pipes (French Drains)

Used in problem drainage zones:

Collect water below turf and redirect it.
Often installed beneath or alongside the compacted base.
Work well in clay soils or low spots prone to pooling.

How to Prepare Ground for Fake Grass Drainage

Ground Preparation & Excavation

Excavate 3–6 inches deep.
Remove all organic matter, including roots and topsoil.
Level the ground and establish a slight grade.

Laying the Base Layer

Install 3–4 inches of crushed stone or gravel.
Use a compactor to press the material in place.
Maintain slope for runoff.

Integrating Drainage Layers

Lay geotextile fabric directly over the compacted base.
If needed, install drainage panels or pipes under or within the base.
Ensure that water flows away from the area (toward a drain or swale).

Best Material for Artificial Grass Drainage in Clay Soil

Clay soil is notorious for trapping water. Solutions include:

Double base layers: Gravel at the bottom, Class II base on top.
Drainage grids: Create a buffer and channel water through.
French drains: Collect and redirect excess moisture.
Avoid sand or DG directly on clay—they will trap moisture.

If you're also dealing with broader soil issues beyond artificial turf, here are some helpful strategies to fix clay lawn drainage effectively.

Regional Drainage Tips: Adapting to Your Environment

Clay Soil Considerations

Poor permeability demands extra drainage planning.
Use grids, pipes, and thicker gravel layers.

Sandy or Loose Soil Adjustments

Risk of base shifting or washing out.
Reinforce with a compacted layer of gravel and geotextile.

High Rainfall Areas

Use drainage panels and pipes under base.
Install with a steeper slope (2% or more).
Extra compaction to resist washout.

Artificial Grass Installation: Maintaining Proper Drainage

Regular Cleaning & Inspections

Remove leaves and debris regularly.
Check for puddles after rain—they may indicate sub-base failure.

Fixing Drainage Problems

Lift the turf to inspect the base.
Re-level or replace compacted areas.
Add additional drainage layers if needed.

Common Installation Mistakes That Disrupt Drainage

Skipping Excavation or Base Prep

Installing directly over soil leads to:
- Water pooling
- Weed growth
- Turf movement

Using Non-Porous Materials

Avoid materials like:
- Regular dirt
- Non-washed sand
- Concrete without slope or drainage

These trap water and damage turf over time.

Forgetting the Weed Barrier

Weed barrier:
- Prevents contamination of base
- Blocks weed growth
- Keeps drainage system clean

FAQs About Artificial Grass Drainage