Extensive Green Roof System

Drainage layer:

• Protecto-drain 20P perforated drainage sheet.

• Thickness: 20 mm.

• Can be cut and shaped around particular details.

Geotextile filter fleece:

• Weight: 100–1200 g/m² (generally 300 g/m² required for component green roof systems).

• See clause 360 for product descriptions.

• Laid above and below drainage layer.

Growing medium:

• Crushed lecca / crushed brick / crushed concrete.

• Green waste (up to 30%).

• Locally sourced marine aggregate and grit.

• Peat (10%).

• Moisture retention polymer.

• 12–14 month release fertilizer, if required.

Vegetation:

- Plug planted extensive roof:

• Requires 150 mm (maximum) substrate.

• Plug planted vegetation installed on site.

• Large variety of foliage available.

• Very low lead times.

• Can be installed at any time of year.

• Can take up to 24 months to be fully established.

• Less rainwater runoff (60% (maximum) retained).

• Requires higher maintenance.

• Saturated weight: Up to 150 kg/m², depending on vegetation.

- Sedum blanket:

• Requires minimum 70 mm substrate.

• Supplied in nine month old, established blanket, to give instant green roof.

• Very low maintenance; weed clearance required once per year.

• Drought resistant; little irrigation required.

• Approximate saturated weight: 80 kg/m².

- Sedum/ wildflower blanket:

• Requires minimum 70 mm substrate.

• Plug planted mixture and established into thin layer of substrate.

• Native, local plants can be used, including herbs, bulbs and heather.

• Can take up to 24 months to be fully established.

• Fairly low maintenance depending on vegetation.

• Approximate saturated weight: 80 kg/m².

Maximum roof slope:

15°.

Protection board:

• Polymeric Protecto-Board.

• Thickness: 3 mm.