Artificial Grass Drainage
Done properly, artificial grass drains as well as a natural lawn or better. The trick is designing the water's route before you install, through the backing, the base and away from the garden.
One of the most common worries about artificial grass is water: where does the rain go? The honest answer is that a well-designed installation drains freely, often better than the tired, compacted lawn it replaces. Problems only appear when drainage is treated as an afterthought rather than designed in from the start.
This page is about water management: the permeable backing, porous base, falls and drainage features that move rainwater away. It sits alongside our ground preparation page, which covers building the structural sub-base. Getting both right is far easier before installation than fixing a soggy lawn afterwards.
Permeable throughout
Perforated grass backing over a free-draining aggregate base lets rain pass straight through to the ground below.
Falls built in
A gentle, consistent fall screeded into the base guides surface water towards a drain or soakaway.
Solutions for hard cases
Soakaways, French drains and extra base depth for clay, waterlogged ground or laying over concrete.
How artificial grass drains
A correctly installed lawn drains vertically. Quality grass has a perforated backing, with small drainage holes punched across it, so water passes straight through the carpet rather than sitting on top. Beneath it, the MOT Type 1 sub-base and a sharp sand or granite dust levelling course are porous, letting that water percolate down into the subsoil below.
Because the whole build-up is designed to let water through, a typical lawn copes with ordinary British rain without any special features at all. It is heavy ground, poor subsoil or hard surfaces underneath that call for the extra measures below.
Falls, soakaways and French drains
Where water needs help on its way, a few tried-and-tested features do the job:
- Falls: a slight slope, often around 1 in 40 to 1 in 80, screeded into the levelling course so surface water runs towards where you want it to go rather than pooling in the middle.
- Soakaway: a stone-filled pit dug below the base that collects water and lets it disperse slowly into the surrounding ground. Useful where there is nowhere obvious for water to run off to.
- French drain: a perforated pipe laid in a gravel-filled trench that intercepts water and carries it away to a soakaway or surface-water drain. Ideal along the low edge of a sloping or waterlogged garden.
Which combination is right depends entirely on your ground, which is why it pays to assess drainage on site before quoting.
Clay and waterlogged ground
Clay and other heavy soils drain slowly, so water that passes through the grass can back up if it has nowhere to go. The subsoil, not the grass, is the limiting factor here. On this kind of ground we typically increase the depth of the free-draining aggregate base so it holds more water temporarily, and add a soakaway or French drain to give that water a route away.
If your garden already puddles or stays boggy after rain with a natural lawn, that underlying issue needs resolving as part of the job. Artificial grass will not cure a drainage problem on its own, but a properly designed installation can manage it far better than bare, compacted soil, so it is worth having us assess the ground before work begins.
Laying over concrete and paving
Hard surfaces change the approach because water cannot drain straight down through them. If the concrete or paving already falls to a drainage point and sheds water well, grass can be laid over it, usually with a foam shockpad underlay, and water runs off across the surface as before. If water pools on the slab, drainage holes can be drilled through to a permeable layer beneath, or the falls corrected first. A smooth, non-draining slab with nowhere for water to go is the one case where drainage must be solved before the grass goes down. Our article on whether artificial grass needs drainage goes into this further.
Benefits and considerations
Benefits
- Rain drains straight through rather than pooling on the surface
- No standing water or boggy patches after heavy rain
- Often drains better than the compacted lawn it replaced
- Drainage features sized to your ground, not a one-size-fits-all guess
- Solutions for clay, slopes, waterlogged gardens and hard surfaces
- Designed in from the start, avoiding costly retrofits later
Worth considering
- Drainage is far cheaper and simpler to design in before installation than to retrofit afterwards
- Heavy clay or a high water table may need a soakaway or French drain, which adds cost
- A soakaway relies on the surrounding ground being able to accept water, so it is not a cure-all
- An existing surface-water or boggy problem must be resolved as part of the job, not ignored
What affects drainage cost
On free-draining ground, drainage is simply part of a standard installation and carries no separate cost. Where the ground is heavy or water has nowhere to go, additional features add to the price, which is one reason fitted lawns range from around £50 to £90 per square metre across the UK, and more in London and the South East.
Key cost factors
- Whether the subsoil drains freely or is heavy clay
- The need for a soakaway, French drain or connection to existing drainage
- Extra excavation depth and aggregate for waterlogged ground
- Correcting falls or drilling drainage holes when laying over concrete
- The size of the area and how much water it has to shed
- Resolving any pre-existing drainage problem before grass is laid
Frequently asked questions
Every lawn needs somewhere for rainwater to go, but most do not need special drainage features. Quality grass has a perforated backing and sits on a porous aggregate base, so water drains straight through. Only heavy clay, waterlogged ground or non-draining hard surfaces call for soakaways or French drains.
It passes through the drainage holes in the grass backing, down through the free-draining sub-base, and into the subsoil below. Where the subsoil drains slowly, a soakaway or French drain collects that water and disperses it away from the lawn.
Not if it is installed for the conditions. On clay we increase the depth of the free-draining base and usually add a soakaway or French drain so water has a route away. The clay subsoil is the real limit, so drainage has to be designed around it.
Yes, provided water can still get away. If the slab already falls to a drain, grass laid over a shockpad sheds water across the surface. If water pools, drainage holes can be drilled through or the falls corrected first.
It can, but it usually means lifting the grass and base to fit soakaways or drains, which is far more disruptive and costly than designing drainage in at the start. This is why we assess how the ground drains before quoting.
Related services and guides
Worried about drainage?
Tell us about your ground, whether clay, slopes, concrete or a garden that puddles, and we will assess it and quote the right drainage solution.