Artificial Grass Specifications Decoded: Pile Height, Density, Backings & Drainage

Artificial grass spec sheets are full of jargon — pile height, Dtex, gauge, backing. Here's what each number actually means and which ones matter for a UK garden.

Pile height — taller is not always better

Pile height is the length of the grass blades, measured in millimetres. UK garden grades typically run from 20 mm (short, manicured look) to 45 mm (lush, natural look). Common sweet-spot for residential use is 30–37 mm — long enough to look natural, short enough to recover well from foot traffic. Anything above 40 mm tends to flatten under regular use and look matted in shaded areas.

Pile weight and density (Dtex)

Dtex measures the weight of an individual fibre — higher Dtex means thicker, stronger blades. Residential grades are typically 8,000–14,000 Dtex. Total weight per m² combines Dtex with pile density (how many tufts per linear metre) and matters more than pile height for long-term durability. Quality residential grass is typically 2,200–3,500 g/m². Anything below 2,000 g/m² will flatten and wear quickly.

Gauge and stitch rate

Gauge is the spacing between rows of tufts (3/8 inch gauge is standard for residential). Stitch rate is the number of stitches per linear metre within each row (16–18 is typical for residential, higher for sports grades). Tighter gauge + higher stitch rate = denser grass that looks more natural and wears better.

Backings — primary and secondary

Behind the visible grass is a primary backing (usually a polypropylene fabric) that the tufts are stitched through, and a secondary backing (typically polyurethane or latex) that locks the tufts in place. The secondary backing is what stops the tufts pulling out. Quality grasses use polyurethane (PU) which is more durable, more flexible in cold weather, and significantly more recyclable than latex. Drainage holes are punched through both backings — typically 4 mm holes every 100 mm for residential.

Drainage performance — the spec that matters most for UK gardens

UK rainfall makes drainage performance the single most important spec for artificial grass. Quality residential backings drain at 60+ litres per m² per minute, more than the heaviest UK rainfall. Cheaper grasses with sparser hole patterns can be 10× slower, which leads to standing water and odour. We test drainage with a bucket-of-water demonstration on every quote — it's the most informative thing we show customers.

Sub-base — the foundation that makes or breaks it

The grass itself is only half the install. A typical residential artificial grass sub-base is: 75–100 mm of compacted Type 1 (or Type 3 for SuDS-sensitive sites), topped with 25 mm of compacted granite dust (laying course), with a weed membrane between the granite dust and the grass. Cheaper installs that lay grass directly onto existing soil look fine for 12 months and then settle, ripple and dip. Spec the sub-base properly and the install lasts 10–15 years.

Infill — do you actually need it?

Older artificial grasses needed sand or rubber infill to keep the pile upright. Modern residential grades with curled or thatched 'memory' fibres are designed to stay upright without infill. We typically only use kiln-dried silica sand infill (about 5 kg per m²) where pet odour management matters or where the grass is on a high-traffic route — it helps with both.

Pet-safe specifications

If you have dogs, three things matter: (1) anti-bacterial backing or backing finish; (2) high drainage rate (urine needs to flush through quickly); (3) silica sand infill that absorbs odour. Several brands now market 'pet-safe' or 'urine-resistant' specs — they generally meet these three criteria and command a small premium (~£3 per m²).

UK fire-rating and child-safety standards

For residential gardens, the only widely-relevant test is the EN 14041 fire classification (Bfl-S1 is standard). For school or nursery installations, a Critical Fall Height (CFH) test under BS EN 1177 may be required — typically achieved by adding a 25–35 mm shock pad layer underneath the grass.

What we include in every artificial grass quote

Our free instant quote tool produces a detailed spec for your project: pile height, total weight, drainage rate, backing type, sub-base spec, weed membrane, infill (if any) and edging method. If you're comparing quotes from other installers, ask for the same spec details in writing — vague quotes like '30 mm artificial grass' tell you almost nothing about the actual product.

Frequently Asked Questions

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