What Does a Green Roof Cost?
Quick Answer
Sedum extensive: £60–100/m². Intensive: £120–250/m².
Based on: supply and installation costs for UK projects (2026). Substrate depth 80–150mm for extensive, 200mm+ for intensive.
Types of Green Roof
- Extensive (sedum): Lightweight, low-maintenance, 80–150mm substrate. Sedums, mosses, wildflowers. £60–100/m²
- Semi-intensive: Grasses, perennials, small shrubs. 150–200mm substrate. £100–160/m²
- Intensive (roof garden): Trees, shrubs, lawns. 200mm+ substrate. £120–250+/m²
- Biosolar (PV + green roof): Combines solar panels with sedum. £100–150/m² (excluding PV)
Build-Up Layers
- Waterproof membrane (root-resistant)
- Protection fleece
- Drainage layer (20–40mm)
- Filter fleece
- Growing substrate (80–150mm+)
- Vegetation (sedum mats, plugs, or seed)
Structural Considerations
- Extensive green roof (saturated): ~80–150 kg/m²
- Intensive green roof (saturated): ~250–500+ kg/m²
- Most flat roofs can support extensive green roofs, but always check with a structural engineer
- Minimum roof pitch: flat to 35° (steeper pitches need retention systems)
Benefits
- Reduces rainwater runoff by 50–70% (SuDS compliance)
- Improves thermal insulation
- Extends membrane lifespan (protects from UV and temperature extremes)
- Supports biodiversity (meets biodiversity net gain requirements)
Last updated: April 2026. Costs are indicative UK averages. Check structural capacity before installation and ensure the waterproof membrane has a root barrier or is root-resistant.