Pipes, Drainage & Ducting
GeoDrain GR 20/200 – Green Roof Drainage Board with Water Storage (20 mm)
A green roof drainage board that stores water as well as shedding it. The 20mm perforated HDPE dimple cells hold 6 litres of rainfall per m² against the build-up and release it back into the growing medium through dry periods, while excess above the reservoir volume discharges through the perforated crowns so the substrate never waterlogs. Compressive strength of 200 kN/m² protects the waterproofing beneath during substrate placement and maintenance traffic. Supplied in 2.4m x 20m rolls covering 48m².
Overview
GR 20/200 is a perforated HDPE green roof drainage board with a 20mm dimple profile, engineered for extensive green roof systems, roof gardens and terraces where the substrate is shallow and the tolerance between drought stress and waterlogging is narrow.
The dimple cells act as reservoirs. Rainfall collects in them and is held against the roof build-up rather than being discharged immediately, then released back into the growing medium by capillary action and evaporation through dry periods. The board holds 6.0 litres per square metre, the equivalent of 6mm of rain, which reduces irrigation demand across the planted area and buffers stormwater discharge from the roof - relevant on any site carrying attenuation obligations. Excess water above the reservoir volume drains away through the perforations in the top of each dimple and moves laterally through the void beneath at up to 10.6 litres per second per metre width, so the substrate never waterlogs and the root zone stays aerated. That same void vents water vapour forming beneath the system laterally, rather than allowing it to pressurise the waterproofing.
GR 20/200 is supplied as a bare board and requires a filtration geotextile laid over it before substrate placement. This is not optional detailing. Growing medium washing into an unfiltered drainage layer will progressively pack the reservoir cells and the void beneath them, and a green roof drainage layer packed with substrate is not recoverable without stripping the roof. Where site programme or wind exposure makes handling a separate filter roll a risk, specify the bonded-geotextile variant instead.
The board also protects the waterproofing membrane and root barrier beneath it from mechanical damage during substrate placement and subsequent maintenance traffic, at a compressive strength of approximately 200 kN/m2 - around 20 tonnes per square metre, which absorbs saturated substrate, ballast margins and barrow loading without the dimples deforming and closing the drainage path. At 2.4m wide it covers ground faster than 2m civil rolls, a real programme saving over a large roof area.
Manufactured from HDPE that resists plant root penetration, decay, groundwater chemistry, acids, alkalis, oils and solvents, and is not harmful to drinking water, permitting use above potable storage and rainwater harvesting systems. Service temperature range of -30 to +80 degrees Celsius. Supplied in 2.4m x 20m rolls and installed horizontally, dimples uppermost, with the filtration geotextile and substrate placed over. Store and transport rolls upright, protected from UV, and cover promptly after laying. Specify GeoDrain RB 40 root barrier beneath the board where the waterproofing system is not itself root-resistant, and ensure all board edges drain freely to roof outlets or perimeter channels.
- MaterialHDPE (high density polyethylene)
- Structure20mm perforated dimpled core with water storage reservoir cells
- ColourBlack
- StandardRoot, chemical and solvent resistant; potable water safe
- Roll Width2.4 m
- Roll Length20m (48 sqm)
Typical Properties
| Property | DS 8-600 | GEO 8-250 | GEO 10-400 | GR 20/200 |
|---|---|---|---|---|
| Type | Bare HDPE | Geocomposite | Geocomposite | Geocomposite |
| Dimple Height | 8mm | 8mm | 10mm | 20mm |
| Compressive Strength | 250 kN/m² | 250 kN/m² | 400 kN/m² | 200 kN/m² |
| Filter Layer | None | Bonded PP | Bonded PP | Separate PP |
| Roll / Sheet Width | 2.0m | 2.0m | 2.0m | 2.4m |
| Roll / Sheet Length | 20m | 20m | 12.5m | 20m |
| Perforated | No | No | No | Yes |
| Coverage | 40 m² | 40 m² | 25 m² | 48 m² |
| Water Storage | - | - | - | 6.0 L/m² |
| Primary Application | Protection | Standard drainage | Heavy-duty drainage | Green roofs |
Note: The above specifications represent the product family properties. Please refer to the product datasheet for individual SKU values.
Typical Applications
View all applicationsBasement & Foundation Waterproofing Protection
GeoDrain DS 8-600 is an 8 mm, 250 kN/m² bare HDPE dimpled protection sheet for basement walls, foundations and below-ground waterproofing systems. Installed outside the waterproofing layer, it provides mechanical protection and creates a defined drainage and ventilation cavity between the structure and surrounding backfill. Specify where an integral filter geotextile is not required.
Retaining Wall & Below-Ground Drainage
GeoDrain GEO 8-250 combines an 8 mm, 250 kN/m² HDPE drainage core with bonded PP filter geotextile for retaining walls, basement walls and foundation drainage. The geotextile filters surrounding soil fines while allowing water to enter the drainage core and discharge toward the designed subsoil drainage system, combining filtration, drainage and waterproofing protection in one layer.
Deep Basement, Podium & Underground Structure Drainage
GeoDrain GEO 10-400 is the heavy-duty drainage geocomposite for deep basements, podium decks, underground parking, tunnels and demanding civil structures. The 10 mm HDPE drainage core provides 400 kN/m² compressive resistance with bonded PP filtration geotextile and published in-plane flow capacity of 4.11 × 10⁻³ m²/s at 20 kPa, i=1, providing drainage and filtration under higher imposed loads.
Green Roof, Planter & Podium Landscape Drainage
GeoDrain GR 20/200 is a perforated 20 mm HDPE drainage and water-storage board for extensive green roofs, roof gardens, planter boxes and landscaped podiums. The system provides 200 kN/m² compressive strength, 6.0 L/m² water storage and 10.6 L/s·m drainage capacity, retaining useful moisture within the planted build-up while allowing excess water to discharge toward roof outlets
Compatible Systems
View all systemsGeoDrain DS 8-600 – 8mm HDPE Dimpled Drainage & Protection Board, 250 kN/m²
Bare HDPE dimpled drainage and waterproofing protection sheet for basements, foundations, retaining walls and below-ground structures. The 8 mm profile and 250 kN/m² compressive class provide a continuous protection and drainage cavity between the waterproofing system and backfill where an integral filter geotextile is not required. A high-volume choice for basement waterproofing protection, foundation drainage and general civil construction.
GeoDrain GEO 8-250 – 8mm Geocomposite Drainage Board for Basements & Retaining Walls, 250 kN/m²
Geocomposite drainage sheet combining an 8 mm HDPE drainage core with bonded PP filter geotextile for filtration, drainage and waterproofing protection in one layer. Designed for retaining walls, basement walls, foundations, planter walls and other below-ground applications where soil fines must be filtered before water enters the drainage cavity. Specify GEO 8-250 where an integrated filter layer is required.
GeoDrain GEO 10-400 – 10mm Heavy-Duty Geocomposite Drainage Board, 400 kN/m²
High-performance geocomposite drainage sheet for deep basements, retaining structures, underground parking, podium decks, tunnels and demanding civil works. The 10 mm HDPE drainage core provides 400 kN/m² compressive resistance with a factory-bonded PP filter geotextile and published in-plane flow capacity of 4.11 × 10⁻³ m²/s at 20 kPa, i=1. Designed for projects requiring higher load resistance and drainage capacity than standard 8 mm systems
GeoDrain GR 20/200 – 20mm Green Roof Drainage & Water Storage Board, 200 kN/m²
Perforated HDPE green roof drainage board for extensive green roofs, roof gardens, planter boxes and landscaped podiums. The 20 mm reservoir profile combines 200 kN/m² compressive strength with 6.0 L/m² water storage and 10.6 L/s·m drainage capacity, retaining useful moisture within the planted build-up while allowing excess water to discharge to roof outlets. Supplied in 2.4 m × 20 m rolls.
Installation Guidance
Standard Method Statement
Substrate Preparation & Product Selection – Confirm the specified GeoDrain grade, compressive strength and filtration requirement before installation. Waterproofing membranes and concrete substrates must be sound, clean and free of sharp projections or debris that could damage the drainage core. Complete and inspect waterproofing before covering it. For horizontal applications, confirm designed falls, drainage outlets and discharge paths before laying the drainage board.
Vertical Installation & Overlaps – Install DS 8-600, GEO 8-250 or GEO 10-400 in the orientation shown on the approved project detail, with geocomposite filter geotextile facing the soil or backfill side. Secure sheets using fixings compatible with the substrate and waterproofing system, keeping penetrations above the waterproofed zone wherever practicable. Form continuous overlaps between adjacent sheets and ensure geotextile overlaps prevent soil fines entering the drainage core. Do not leave open joints, displaced fleece or exposed drainage edges.
Drainage Outlet & Backfilling – The drainage layer must terminate into a designed collection and discharge system such as a perforated subsoil drain, drainage channel or approved outlet. Maintain an uninterrupted drainage path at the base of walls and around penetrations. Backfill carefully to prevent displacement, puncture or crushing of the sheet, avoiding direct impact from large aggregate or compaction equipment. GEO 10-400 provides 400 kN/m² compressive resistance where higher imposed loads require a heavy-duty drainage geocomposite
Green Roof & Podium Installation – Install GR 20/200 horizontally over the completed waterproofing/protection build-up with the reservoir and perforation arrangement positioned in accordance with the approved green-roof detail. Maintain free drainage to roof outlets and perimeter channels and install a suitable filter geotextile above the board before placing growing medium where required. GR 20/200 provides a 20 mm profile, 200 kN/m² compressive strength, 6.0 L/m² water storage and 10.6 L/s·m drainage capacity
Quality Assurance & Testing
Field QA/QC Checklist
- Delivery & Storage: Materials checked against the delivery note and conformance certificates, stored off the ground, covered from UV and kept clear of sharp objects and fuel.
- Orientation: Dimples placed against the structure or soil as specified; filter fabric facing the backfill.
- Laps & Fixing: Vertical and horizontal laps and fixing points to the manufacturer's guide; top edge closed with a finishing strip.
- Drainage Outlet: Base connected to the drainage pipe or outlet; falls checked.
- Backfill: Backfill placed in layers without tearing the fabric or crushing the board.
Manufacturing Standards
- ISO 12958 in-plane flow capacity
- Manufacturer installation guide
- Root, chemical and solvent resistant; potable water safe
Documents
Product Selection Guide
Compare performance properties across the entire category hierarchy before specifying.
Installation & Method Statement
Standard deployment procedures, installation specifications, and field application method statements.
QA/QC Site Checklist
Field quality control procedures, inspection checklists, and testing standards to verify installation integrity.
Technical Data Sheet (TDS)
Guaranteed minimum average roll values (MARV) and material testing properties.
Chemical Resistance / Accessories Guide
Chemical compatibility matrix and list of auxiliary materials needed for installation.
Projects Using GeoDrain GR 20/200 – Green Roof Drainage Board with Water Storage (20 mm)
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