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TerraLawn & Paving

Guide · 5 min read

What Goes Under Artificial Grass? (Base Preparation Explained)

The turf is the part you see. The base is the part that determines whether the lawn still looks and drains well in three years' time.

Direct answer

A proper artificial grass base is a compacted layer of crushed stone (a sub-base, sometimes with a separate base course), built up in stages and compacted after each layer, finished with a thin bedding layer and a permeable weed membrane before the turf is laid. It exists to provide stable, even support and fast drainage. Poor compaction is the leading cause of a synthetic lawn that sinks, puddles or develops an uneven surface.

Why the base matters more than the turf

Artificial turf itself is a manufactured product with fairly consistent quality across reputable ranges. What varies enormously — and what actually determines whether an installation holds up — is what happens before the turf is even unrolled. A well-built base drains a downpour within minutes and stays flat under years of foot traffic. A poorly built one holds water, settles unevenly, and can leave the turf looking rippled or sunken in patches.

What the base is made of

The typical build-up is a compacted crushed stone layer (often referred to as a sub-base), which provides the load-bearing structure and, critically, the drainage path for water to move down and away rather than sitting at the surface. This is laid in stages — spread, then compacted, sometimes repeated in more than one lift — rather than dumped and compacted in a single pass, which tends to leave the lower material under-compacted.

Above that sits a thinner bedding or blinding layer, which creates a smoother, more even surface for the turf and membrane to sit on, followed by the permeable weed membrane itself.

Why compaction is the step that gets rushed

Compaction takes time and equipment, and its effects aren't visible once the turf is down — which makes it the step most likely to be shortcut on a rushed or underpriced job. The consequences usually show up months later, not on installation day: soft spots, shallow depressions where foot traffic concentrates, or water pooling after rain instead of draining through.

Drainage and falls

Beyond compaction, the base also needs to be graded with a slight fall so water has somewhere to go, rather than being perfectly flat. Where a garden sits close to a boundary wall, a building, or a lower-lying neighbouring property, the fall and any drainage outlets need to be planned so water is directed appropriately rather than simply moved from one problem spot to another.

Ground conditions that change the approach

Not every site starts from the same conditions. Heavy clay soils, areas with a high water table, or ground that has been built up with poor-quality fill in the past may need additional depth, a different base material, or supplementary drainage (such as a perforated pipe tied into an outlet) to perform properly. This is typically assessed on site rather than assumed from a standard specification.

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