Installing synthetic grass on soft ground is not just about unrolling a roll on the soil. The quality of the result depends almost entirely on what happens before the installation: the preparation of the ground, the choice of the underlayer, and the management of drainage determine the durability of the covering for several years. The installation of synthetic grass on soil follows a precise logic, where each step influences the next.
Soil permeability and drainage: the parameter that tutorials overlook
Excavation and leveling are not enough: the drainage of the soil upstream determines the longevity of the installation. Clay soil does not react like sandy soil in the face of rain. If water stagnates under the artificial lawn, pockets of moisture form, promoting odors and destabilizing the surface.
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Before touching anything, observing the behavior of the ground after heavy rain provides valuable insight. Soil that remains waterlogged for several hours requires more extensive drainage work than filtering soil. In some cases, a soil permeability study can determine whether a bed of gravel or crushed sand is sufficient, or if a peripheral drain is necessary.
Successfully installing synthetic grass on soil involves this initial assessment, often overlooked by amateur installers.
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Preparing the ground on soft soil: excavation and compaction
Excavation involves removing the existing vegetation layer by a few centimeters. The goal is to obtain bare, clean soil, free of any roots and organic debris. Leaving plant residues under the geotextile creates a fertile ground for weeds, exactly what we want to avoid.
Leveling without cheating on the slope
A perfectly flat surface is not the goal. A slight slope facilitates the natural drainage of water and protects the artificial grass from moisture accumulation. Feedback on the ideal slope varies, but the idea remains the same: water must be able to flow to a low point, a flowerbed, or a drain.
Compaction is ideally done with a garden roller or a vibrating plate for large areas. Compacting in multiple passes, crossing directions, yields a more uniform result than a single heavy pass.
The sand layer: thickness and grain size
Spreading a layer of crushed sand (not beach sand, which is too fine and unstable) creates a regular base. Guides generally mention a thickness of a few centimeters, compacted with a roller. Crushed sand has an advantage over round sand: its angular grains interlock and resist settling better over time.
- Remove the vegetation layer and roots over the entire surface, leaving no residual organic matter.
- Compact the soil in multiple crossed passes with a roller or vibrating plate.
- Spread crushed sand a few centimeters thick, then compact again to achieve a stable and slightly sloped surface.
Anti-regrowth geotextile: choice of weight and installation
The geotextile serves two functions: blocking the regrowth of grasses and separating the sand from the soil below to prevent the layers from mixing over the seasons. A geotextile that is too light tears during installation or punctures under persistent roots. A sufficiently dense weight ensures an effective barrier over time.
The strips of geotextile must overlap by several centimeters to leave no gaps. This overlap is often underestimated: a gap of a few centimeters is enough to allow vigorous weeds like couch grass or bindweed to pass through.
PFAS regulation and artificial grass: what changes in the short term
The chemical composition of synthetic lawns is directly affected by upcoming restrictions. Products containing intentionally added PFAS will no longer be manufactured or sold starting in 2027, with a specific category dedicated to artificial grass starting in 2029. Meanwhile, France adopted a PFAS restriction law in 2025 and an implementing decree aiming for a 70% reduction in PFAS emissions by 2028.
For an individual investing in synthetic grass today, this means that the available ranges will evolve. Checking the product composition before purchase, by requesting a technical data sheet from the supplier, allows for anticipation of potential future restrictions. The available data does not yet allow for conclusions about the concrete impact of these standards on prices or the availability of consumer products.
Fixing and finishing synthetic grass on soil
Once the grass is unrolled and cut to the desired dimensions, peripheral fixation with pegs or U-nails keeps the edges in place. On soft soil, this step is more critical than on concrete slabs: the ground shifts slightly with variations in humidity and temperature.
The joints between the strips deserve special attention. Two misaligned strips create a visible line that never disappears. Orienting all the fibers in the same direction and checking the alignment before fixing anything avoids costly time-consuming corrections.
- Unroll the strips in the same direction of fiber for a uniform visual effect.
- Let the grass rest for a few hours before fixing, allowing it to relax and adapt to the surface.
- Brush the fibers against the grain with a broom to straighten the strands crushed by the roll packaging.
Regular maintenance is limited to occasional brushing and rinsing. With the ban on synthetic mineral fertilizers in gardens set for January 1, 2027, the transition areas between artificial grass and planted spaces will need to be managed differently, favoring organic amendments for planted borders.
A well-drained, properly compacted area protected by suitable geotextile provides a base on which even entry-level grass will last several years without deformation or unpleasant surprises.