Product grades and cost breakdown
Artificial grass is graded by pile height (15mm–50mm), face weight (dtex — a measure of yarn density), and stitch rate (stitches per 10cm). For residential use in London, the practical range is 25mm–40mm pile with a face weight of 13,000–20,000 dtex and a stitch rate of 16–20/10cm. Products in the 30–35mm range at 15,000–17,000 dtex represent the best value for rear gardens: soft underfoot, realistic in appearance, and durable for 12–15 years under normal family use. Products below 10,000 dtex face weight have a thin, matted appearance after 2–3 seasons and are not recommended for permanent installation. Silica sand infill (typically 4–6kg/m²) stabilises the pile and improves underfoot feel; kiln-dried rubber crumb (recycled tyres) is increasingly avoided due to microplastic concerns. Installation cost breakdown: excavation and disposal of existing turf (£5–£12/m²), 100mm MOT Type 1 sub-base (£8–£15/m²), weed membrane (£1–£2/m²), banding boards and fixings (£2–£5/m for perimeter), artificial grass supply and lay (£20–£65/m² depending on grade). Total installed cost: £40–£110/m².
Drainage, London Clay and SuDS compliance
Artificial grass is technically classified as impermeable surfacing under SuDS guidance — water drains through the backing holes (typically 25–35 holes per m²) rather than through the surface itself. On London Clay, where natural drainage is already poor, this drainage hole specification is typically adequate for a rear garden receiving normal rainfall, provided the sub-base is correctly graded and the grass is pitched at a minimum 1:80 fall toward a border or drain. Front garden artificial grass over 5m² falls within the same SuDS rules as hard paving — technically impermeable, it requires drainage directed to a lawn or soakaway. In practice, many London front gardens install artificial grass with a perimeter drainage channel rather than a compliant permeable surface, which is non-compliant; planners in Lewisham, Lambeth and Southwark have issued enforcement notices for this. The safest front-garden solution is natural turf or permeable resin-bound gravel rather than artificial grass. Several London boroughs — Hammersmith & Fulham, Islington — have adopted planning policies discouraging artificial grass on grounds of urban heat island effect and biodiversity loss; check local policy before specifying.
