Artificial Grass Drainage Base: What Goes Under Artificial Grass?
An artificial grass drainage base is the prepared build up beneath synthetic turf. It creates a stable surface, supports the finished lawn and gives rainwater a planned route away from the area.
The correct base is not identical for every installation. Existing soil, rainfall, slope, traffic, turf backing, nearby buildings and the available drainage outlet all affect what should go underneath the grass. A residential garden on firm, free draining ground may need a different build up from a clay site, school play area, rooftop or concrete patio.
This guide explains the main layers, the questions that should be answered before work begins and the warning signs that indicate a drainage problem.
Quick Answer
What goes under artificial grass? A typical installation over soil may include prepared and compacted ground, a permeable geotextile separation layer where required, a compacted free draining aggregate base, a thin levelling layer, an optional shock absorbing layer, the artificial grass and a compatible infill. The exact materials, depths and drainage details must suit the product and site.
Why Is the Base Under Artificial Grass Important?
The base beneath artificial grass affects drainage, surface level, stability and long term performance. Turf laid over poorly prepared ground can develop dips, soft patches, visible joins or waterlogged areas even when the grass itself has a perforated backing.
Drainage depends on the entire route that water follows. Water must pass through or across the turf, move through the supporting layers and reach a suitable outlet or ground that can accept it. A permeable turf product cannot solve a blocked outlet, unsuitable soil or a base that traps water.
The base also needs to remain stable under the expected use. A decorative garden, pet area, busy walkway and play space place different demands on the surface. The selected system should therefore match the application rather than follow one standard recipe.
What Goes Under Artificial Grass?
A complete artificial grass system is built in layers. Some projects use all the layers below, while others require a different engineered solution. The turf supplier or installer should confirm compatibility before materials are ordered.
1. Prepared Ground or Existing Surface
What is the subgrade under artificial grass?
The subgrade is the ground that supports the installation. Organic material, loose soil, roots and unsuitable debris should be removed. The remaining ground should be shaped and prepared so it can support the base without excessive movement.
Soft spots, expansive clay, buried services and signs of persistent moisture should be investigated before the surface is covered. Installing turf over unstable ground may hide the problem temporarily, but it does not correct it.
2. Geotextile Separation Layer
Does artificial grass need geotextile fabric?
A permeable geotextile may be used to separate the prepared ground from the aggregate base. It can help limit the movement of fine soil into the stone while allowing water to pass through, provided the selected fabric suits the application.
A geotextile is not a substitute for drainage design. The position and type should be specified carefully because a poorly chosen or clogged layer may restrict water movement. Weed control also depends on preparation, edges and ongoing maintenance, not only on a membrane.
3. Permeable Structural Base
Which base material should be used under artificial grass?
A compacted, well graded aggregate is commonly used to create a firm and permeable structural base. The exact stone specification and installed depth should reflect the soil, intended traffic, excavation depth, drainage design and turf system.
Angular aggregate generally interlocks more effectively than loose rounded stone. However, regional material names such as crusher run, G5 or G7 do not automatically confirm drainage performance. The supplier or installer should verify grading, fines content, compaction method and compatibility with the design.
4. Levelling Layer
Why is a levelling layer used under synthetic turf?
A thin levelling layer can refine the final levels and create a smooth surface beneath the turf. Suitable materials may include specified crusher dust, grit or another product approved for the system.
This layer should not be used to correct a weak or badly shaped base. Excessive fine material can retain water or move over time. The supporting aggregate should already be stable and correctly profiled before final levelling begins.
5. Optional Shock Absorbing or Drainage Layer
When is a shockpad needed under artificial grass?
A shock absorbing layer may be required for play areas, sports applications or spaces where a softer surface is part of the design. The pad should be compatible with the turf, drainage plan and required performance standard.
Thickness alone does not prove safety. Where play equipment is installed, the complete surface system should be selected and tested for the relevant use and potential fall height. Rooftops and balconies may instead need a specialised drainage mat that protects the waterproofing and channels water toward existing outlets.
6. Artificial Grass and Compatible Infill
Does every artificial grass product need infill?
No. Infill requirements vary according to the turf product and application. Some systems use kiln dried silica sand or another specified infill to support the fibres, add ballast and influence performance. Other products may use less infill or be designed differently.
Use only the material and quantity recommended for the chosen turf. Pet areas may need a cleaning and drainage plan that addresses urine and odour, but no infill can compensate for poor falls or trapped water.
Buyer Tip
Ask for the complete installation specification, not only the turf name. The base materials, depths, edge details, drainage route, infill and maintenance requirements should all be confirmed for the actual site.
How Deep Should an Artificial Grass Drainage Base Be?
There is no universal depth that is correct for every artificial grass installation. Depth depends on the stability and drainage of the existing ground, expected traffic, aggregate specification, product requirements and whether additional drainage infrastructure is needed.
Domestic landscape installations are often shallower than heavily used play, school or commercial areas, but a fixed number should not be selected before the ground is assessed. Clay, filled ground, vehicle loading and weak areas may require deeper excavation or an engineered build up.
The finished level must also account for door thresholds, paving, kerbs and surrounding ground. Artificial grass should not direct water toward a building or create a raised edge that blocks runoff.
How Should South African Site Conditions Affect the Base?
South African properties vary widely in soil, rainfall patterns, slope and existing drainage. Local conditions should guide the design.
Clay or Slow Draining Soil
Can artificial grass drain over clay soil?
Artificial grass can be installed over clay soil, but the drainage route needs careful planning. Clay may accept water slowly, so simply adding permeable stone above it can create a temporary storage layer without a reliable outlet.
The solution may involve reshaping the area, increasing the base, installing collection drains or directing water to an approved discharge point. The correct approach depends on the site and should avoid sending water toward foundations or neighbouring properties.
Sandy or Free Draining Ground
Does sandy soil remove the need for a drainage base?
No. Sandy ground may accept water more readily, but the turf still needs a stable, level and restrained base. Loose sand can move, settle or erode if it is not prepared correctly.
Infiltration should be confirmed rather than assumed. A soakaway or infiltration system should only be used after the ground conditions, groundwater, nearby structures and water volumes have been assessed.
Sloping Gardens
Should artificial grass be completely flat?
Artificial grass should look even, but the overall area normally needs a controlled gradient or another drainage route. The direction of the fall must suit the property and discharge water safely.
Steeper slopes also need strong edge restraint and careful fixing to reduce movement. Water flowing from roofs, paving or neighbouring ground should be considered because it may exceed the amount falling directly onto the turf.
Concrete Patios
Can artificial grass be installed on concrete?
Yes, suitable artificial grass can be installed on sound concrete, but water must be able to reach a drain or open edge. Existing cracks, low points and blocked outlets should be addressed before the turf is fixed.
A compatible drainage or cushioning underlay may be required. The installation method should not seal water beneath the surface or damage damp proofing and adjacent building details.
Balconies and Rooftops
What goes under artificial grass on a balcony?
Balconies and rooftops require a system that protects the waterproofing and keeps outlets accessible. A drainage mat or suitable raised system may be used, depending on the structure and turf product.
Do not drill, glue or fasten through waterproofing without approval. Structural loading, wind uplift, fire requirements and building rules may also need professional input.
When Does Artificial Grass Need Extra Drainage?
Additional drainage may be needed when natural infiltration is too slow, the area sits below surrounding ground, runoff enters from other surfaces or there is no safe route for water to leave.
French Drains
A French drain may collect water at a low point or along a boundary and carry it toward a suitable outlet. Its position, pipe, stone surround, fall and discharge point must be designed as one system. Installing a drain with nowhere for the water to go will not solve ponding.
Channel Drains
Channel drains can help intercept water near patios, thresholds and hard edges. They should remain accessible for cleaning and must connect to an appropriate outlet. The surrounding levels should guide water into the channel without creating a trip edge.
Soakaways and Infiltration Areas
A soakaway stores runoff temporarily and allows it to enter suitable ground. It is not appropriate for every property. Soil infiltration, groundwater, nearby structures, contamination and the expected water volume should be assessed before one is used.
The guidance from Susdrain on infiltration systems explains why infiltration features require site specific investigation rather than assumptions based only on the visible soil.
What Base Is Needed for Different Artificial Grass Uses?
Residential Gardens
A home lawn needs a stable, even base that manages rainfall and normal family use. The design should also account for garden irrigation, roof runoff, tree roots and future access to services.
Pet Areas
Pet areas need free drainage, practical edges and a cleaning routine. Urine must be able to move through the turf and away from the area rather than collect beneath it. Confirm that the turf, backing, infill and cleaning products are compatible.
Schools and Play Areas
Busy play areas require a base designed for repeated use and stable transitions. Where impact protection is needed, the turf and shock absorbing layer should form a tested system suitable for the equipment and use. Drainage points should be protected but remain serviceable.
Commercial and Sports Areas
Commercial walkways and sports surfaces may need engineered levels, heavier duty base construction and performance testing. FIFA notes that artificial pitch design is site specific and depends on ground conditions, load bearing capacity and an approved drainage outlet.
For larger sporting projects, review the FIFA guidance on turf and pitch design and obtain a specification suited to the intended sport and performance level.
How Is an Artificial Grass Drainage Base Installed?
A professional installation sequence should be adapted to the site, but the following process explains the main quality checks.
1. Inspect and Plan the Site
Identify existing drainage, soil conditions, low points, thresholds, services and incoming runoff. Confirm where water will discharge before excavation starts.
2. Excavate and Prepare the Ground
Remove vegetation, organic matter and unstable material to the required depth. Correct soft spots and shape the formation level to support the drainage design.
3. Install Separation and Drainage Components
Place the specified geotextile and any pipes, channels or outlets without wrinkles, blockages or unplanned dams. Protect drainage components during later compaction.
4. Build and Compact the Structural Base
Install the specified aggregate in manageable layers and compact it with suitable equipment. Check levels and stability throughout the process rather than waiting until the turf is laid.
5. Apply the Levelling Layer
Use only enough approved material to refine the surface. The completed base should be smooth, firm and correctly profiled without loose ridges or deep fine material.
6. Install Edges, Turf and Infill
Secure the perimeter without blocking drainage. Lay the turf in the planned direction, form neat seams and apply compatible infill where the product requires it.
7. Test the Finished Drainage Route
Check that water moves away from thresholds, walls and low areas and reaches the intended outlet. A surface test can reveal obvious ponding, but it does not replace proper assessment of the base and discharge system.
What Are the Signs of a Poor Artificial Grass Base?
Early signs include standing water that remains long after rain, soft or pumping patches, dips, lifted edges, opening seams and water collecting against walls. Persistent odour in a pet area may also indicate that liquid is not leaving the system effectively.
The visible symptom does not always identify the cause. Ponding may result from blocked turf perforations, compacted fines, incorrect levels, a damaged outlet or slow ground infiltration. The area should be assessed before extra sand or another surface layer is added.
How Do You Maintain Artificial Grass Drainage?
Remove leaves and debris before they break down and clog the surface. Brush the turf using the method recommended by the manufacturer and keep channels, inspection points and outlets clear.
Rinse pet areas as required using compatible products and monitor whether water drains normally. Avoid harsh chemicals unless the turf supplier confirms they are suitable. If new ponding, settlement or odour develops, investigate the cause rather than masking it.
Browse Carpet & Decor’s range of artificial grass products when comparing options for gardens, play areas, sport and commercial spaces.
Choose the Base Before You Choose the Finish
A successful artificial grass installation begins below the visible surface. The ground must be stable, the base must suit the expected use and water must have a complete route to an appropriate outlet.
Carpet & Decor can help you compare artificial grass options and discuss installation requirements for your property. The final base specification should be confirmed after the site, product and intended use have been considered together.
Frequently Asked Questions
What is the best base to put under artificial grass?
The best base is a stable, compacted and free draining system specified for the site and turf product. It commonly includes prepared ground, a suitable geotextile, compacted graded aggregate and a thin levelling layer. Soil type, traffic, rainfall, thresholds and the available drainage outlet should determine the exact materials and depths.
How deep should the base be under artificial grass?
There is no single correct depth for every installation. A domestic garden on stable ground may need a different build up from clay soil, a school play area or a commercial walkway. The installer should determine the excavation and base depth after assessing ground stability, drainage, expected traffic, levels and the turf manufacturer’s specification.
Do I need a French drain under artificial grass?
Not every artificial grass installation needs a French drain. It may help where water collects at a low point, slow draining soil cannot accept runoff or water must be intercepted near a boundary. The drain still needs the correct fall and a suitable outlet. A site assessment should confirm whether it is necessary.
Can artificial grass be laid directly on soil?
Artificial grass should not normally be laid directly over loose, organic or unstable soil. The area generally needs excavation, preparation and a compacted base that supports the turf and manages water. The precise build up depends on the ground and product. Direct installation can lead to movement, weeds, uneven levels and poor drainage.
Can artificial grass be installed over concrete?
Yes, artificial grass can be installed over sound concrete when the surface drains to an open edge or suitable outlet. Cracks, low points and blocked drains should be corrected first. A compatible drainage or cushioning layer may be required, and the fixing method should not trap water or damage nearby waterproofing details.
